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2 year anniversary

Can I continue on the INTERVAL study after 2 years?

Yes you can. Close to your 2-year donation you will receive an invite from us to join INTERVAL Phase II. It is entirely up to you if you wish to join. If you do decide to join, you will be able to continue donating at the interval you were allocated at the beginning of the study. If you would like to know more about INTERVAL Phase II, please click here or click the ‘INTERVAL Phase II’ link at the top of the page.

The study information sheet advised that some donors would be invited to take home and wear devices to measure physical activity over a period of seven days – will I be invited?

At the time of your 2-year anniversary of joining INTERVAL we will send you a link to an online questionnaire to complete. In this questionnaire we will ask you if you are willing to wear a physical activity monitoring device over a period of 7 days. Your permission will also be sought to retrieve your name and address for the purposes of sending the device in the post. We will be randomly selecting individuals to take part in these measurements; therefore, even if you are willing to take part, you may not be selected.

What will happen after my 2-year INTERVAL donation?

Your 2-year donation may be made several days or weeks before your 2-year anniversary of joining INTERVAL. At this 2-year anniversary date we will send you a link to an online questionnaire to complete. The information you provide in this questionnaire will be very important to the findings of the research.

What will happen at my 2-year INTERVAL donation?

In addition to your usual donation we will collect an additional small sample of blood for our research; this will be similar to the sample we collected at the beginning of the study. This sample will be very important to the findings of the research.

What will happen if I am deferred at the time of my 2-year INTERVAL donation?

Although you will not be able to give your usual donation you will still be invited to attend your Donor Centre to give a small sample of blood for INTERVAL; this will be similar to the sample we collected at the beginning of the study. This sample will be very important to the findings of the research. To make an appointment to do this we would be very grateful if you could contact your Donor Centre directly. You can find details for all the centres here.

When will I get to know the results of the study?

All participants will complete their involvement in the study in June 2016. It is only at this point that we will start to analyse the study outcomes. This is likely to take some time and we anticipate that the results will not be available until early 2017. At this time we will widely publicise the results for example in scientific journals, donor communications and on the INTERVAL study website.

General Questions

Are there any risks associated with the study?

You may be asked to give blood more frequently than usual during the study. The main risk of giving blood more frequently than is now standard is iron deficiency and the related anaemia because of a low haemoglobin level. This is why NHSBT will continue to follow its routine safety procedures to monitor your haemoglobin level before donation.

It is important to stress that your safety will be looked after by NHSBT in the same way as before. That is, you will receive the usual ‘finger-prick’ screening test for haemoglobin levels and you will need to be within the safe range to be eligible to donate. If you fall outside this range you will be invited to return again at your allocated interval.

Can I know the results obtained from my blood samples?

There are no plans to feedback results from genetic tests. The only scenario where blood-based test results would be communicated to you would be if we discover anything that has an immediate impact on your healthcare (e.g. in case cells are present in your blood that may point to leukaemia or a very high count of platelets). In this case, the researcher will inform a medical professional about the nature of the problem, and about who you are. The NHSBT medical professional would then use the routine procedures applicable in the NHS to get in touch with you and offer advice which may involve contacting your GP.

Do blood donations in the study still count towards my total number of donations?

Yes, INTERVAL study donations count towards your total number of donations, as normal (i.e. in the same was as all whole blood donations given to NHSBT are currently counted).

How do I withdraw if I want to do so?

The study will be most valuable if few people withdraw from it, so it is important to discuss any concerns you may have with a member of the study team before you agree to participate. However, you can withdraw from the study at any time and without giving a reason but we hope that you will continue to give blood as a regular donor. You can withdraw by telephoning us on freephone 0800 064 0089 Mon to Fri: 9:00 – 17:00, or by emailing or by writing to the coordinating centre. This will allow us to discuss your concerns with you and determine the desired level of withdrawal from the following options:

“No further contact”: This means that the INTERVAL team would no longer contact you directly, but would still have your permission to retain and use information and samples provided previously and to obtain and use further information from your health records.

“No further use”: This means that, in addition to no longer contacting you or obtaining further information about you, any information and samples collected previously would no longer be available to researchers. Please note that we will not be able to remove results of any tests already performed with your samples from the study database but we will prevent your records from being used in any future research. We can also assure you that your blood samples will be removed from the central study repository after we have received your written notification. It will, however, not be possible to remove small volumes of your samples which already have been distributed to research laboratories but results which are generated after you have withdrawn will not be uploaded to the study database. Your signed consent and withdrawal forms will be kept as a record of your wishes.

If, having discussed the options and your concerns, you did decide to withdraw then we would send you a withdrawal form to confirm your wishes in writing. Examples of this form can be viewed here. This form can be completed by you or, if you are not able to do so for some reason (such as illness), by someone able to act on your behalf. In the unlikely event of a loss of capacity to decide on continued participation in the study, the study team would retain blood samples and personal data collected and continue to use it confidentially in connection with the purposes for which consent has been granted.

How is information about me kept confidential?

We protect your privacy at all times.  The steps taken to ensure confidentiality are detailed below:

■ At the donation session, your consent to take part in the study will be recorded on a form that will contain identifiers including your name, email address and mobile phone number. These forms will be stored in a secure location and separately from the study data.

■ Your samples and data will not include any personal identifying details; researchers working with your samples and data will, therefore, never know your identity. Your data will be stored using a unique, anonymous study identification number.

■ A single table linking your anonymous study identification number to your NHSBT Donor Number and your NHS number identity will be stored on a separate password protected location which may be accessed by the study data manager only.

■ The link table will be used to retrieve only relevant health information from your medical and other health-related records. The retrieved information will be anonymous as any personal identifying details will have been removed and replaced by the unique anonymous study identification number.

■ All study data will be stored in a restricted-access, study database. This study database will not be connected to the NHSBT database containing your personal details. The study data will be linked to your study identification number, but your personal details (surname, first name, date of birth, address) will never appear in this database. Access to the study database will be password protected and will be used only by named researchers working on this study under the direct supervision of the senior scientific investigators.

How will I get to know the main findings of the study?

The main findings of the study are expected to be available early in 2017.  At this time we will widely publicise the results for example in scientific journals, donor communications (e.g. the Donor Magazine) and on the INTERVAL study website.

I am expecting a link to the questionnaire but have not received an email – what should I do?

If you have not yet received the email please make sure to check your junk/spam email folder. If the email is not in there then please contact us as we may not have your correct email address.

I don’t want to be in the group I have been allocated to – can I change?

No, participants must be randomly allocated to the different groups.  If participants chose which group they went into, this could introduce bias in the study results, which would then mean that they are not applicable to the wider blood donor population.

I have already joined the study but have become pregnant – does this mean I am no longer on the study?

We want the study to reflect reality as much as possible so you will still remain on the study even though you cannot donate blood.  This means you will still be sent the online questionnaires.  If you want to avoid receiving appointment reminders whilst you are pregnant please call the appointment line on 0300 0200 333.

I have changed my email address, what should I do?

You can contact the study team on 0800 064 0089 or email to let us know and we will update our records so you will continue to receive study correspondence.

I have moved home from University and no longer donate at the same centre. Can I still take part?

Yes, you can continue on the study if you are able to donate at one of the permanent centres. To see a list please click here.

I have received a link to an online questionnaire but not the password – what should I do?

Please check that the email with the password is not in your junk/spam email folder. The email subject is “INTERVAL key”. If you cannot locate the email then please contact us.

I have to call an 0300 number to make my study appointments, how much does it cost?

0300 numbers are charged at the same rate as a local landline call.

I read that my blood samples will be stored for future research – Is my blood donation still used to treat patients?

Absolutely.  Your blood donation is used in exactly the same way as normal, to save and improve lives.  An additional small blood sample (approximately 3 teaspoons) will be collected when you join the study. Another research sample will be collected after 2 years.  These samples are used or stored for research purposes

I’d like to change my donation appointment – will this affect my participation in the study?

This will not affect your participation in the study.  We ask that you stick to your allocated intervals as best you can over the 2-year study period, but we recognise that it may not always be possible for you to do this.

What happens if something goes wrong?

The risk of participants suffering harm as a result of taking part is minimal, and INTERVAL has insurance in place to provide compensation for any negligent harm caused by participation.

What happens to my blood samples?

Blood samples collected for the purposes of the research will either be used immediately, i.e. to perform a full blood count and measure substances related to your body’s iron stores (e.g. ferritin) or will be frozen for use in future research. Stored samples will include separate components of your blood (e.g. plasma, serum and DNA) which will be:

■ Kept securely at central laboratories. They will not be labelled with your name or contact details, but only with a unique study number.

■ Used by the study investigators for medical and health-related studies which have relevant scientific and ethics approval.

■ Used to measure biomarkers, which are substances in the body (e.g. haemoglobin) that can easily be measured and give a clue to health (e.g. iron deficiency).

■ Used to study your DNA and related substances. In particular, we want to know how genes regulate blood cells. Variations in genes influence the behaviour of the blood cells and so we need to analyse your DNA in detail. As part of this study, we will test your DNA for many genes and we may determine the sequence of part of or your entire DNA code.

What is stored in the INTERVAL research database?

Your anonymised data is stored in the INTERVAL study database and used by the study investigators to, for example, understand characteristics (e.g. age and gender) that influence the frequency with which people can donate safely. Stored anonymised data may also be used for future medical and health-related studies which have relevant scientific and ethics approval. Information stored on the database is anonymised and includes:

■ Relevant information from your NHSBT donor record, e.g. gender, month and year of birth, details of your donation history and blood group.

■ Data from the online questionnaires, forms and assessments.

■ Results from all laboratory measurements using your blood components. This includes your genetic information.

■ Information on health outcomes collected from routine medical and other health-related records at the time of joining the study and from time to time thereafter.

What is the point in being in the 12/16 week group if I already donate every 12/16 weeks?

We need a control or ‘usual’ group (i.e. the 12-week group for men and the 16-week group for women) against which to compare the impact of reduced interval groups.  Without a control group we will not be able to produce conclusive evidence on the safety and feasibility of more frequent blood donation.  This group is therefore very important for the study.

When will the main findings of the study be available?

All donors will complete their participation in the study in June 2016.  Around this time researchers will start to analyse the study data to look at differences in the amount of blood donated and measures of well-being between groups of donors who have been giving blood at the various intervals.  This analysis will take several months and therefore the main findings of the study are expected to be available early in 2017.

Where is my nearest donation centre?

There are 25 permanent blood donation centres in England.  Click here to see the locations.

Who can use my information and samples?

Your anonymous information and samples are available only to researchers who have relevant scientific and ethics approvals for their planned research. This could include researchers who are working in other countries and in commercial companies who are looking for new treatments or laboratory tests.

Insurance companies and employers will not be given any individual’s information, samples or test results, and we will not allow access to the police, security services, relatives or lawyers, unless forced to do so by the courts.

There will be a requirement to publish the results of the research arising out of the samples and data collected during the study so that people can benefit from it.

The results will also be made available to participants and anyone else who might be interested on this website.

Who do I contact if I have any concerns?

If you have any concerns or complaints about anything to do with the INTERVAL study then you can telephone the freephone number on: 0800 064 0089 Mon to Fri: 9:00 – 17:00 or email us

Alternatively, if you would like to write to the person in charge, please send your letter to:

Professors John Danesh and David Roberts The INTERVAL Study University of Cambridge Department of Public Health and Primary Care Wort’s Causeway, Cambridge CB1 8RN

We will reply to your letter promptly in writing, unless you enclose your telephone number and wish to discuss your concerns with us.

Who has approved the study?

All research in the NHS is reviewed by an independent group of people, called a Research Ethics Committee which is there to protect your safety, rights, wellbeing and dignity. This project has been reviewed and was given a favourable review by the Cambridge (East) Research Ethics Committee.

Who is organising and funding the study?

The INTERVAL study has been set up by the Universities of Cambridge and Oxford in collaboration with NHSBT, and funding has been provided by NHSBT.

Once funding for the study comes to an end, data and samples collected during the study will be maintained, as a national collection, by the lead academic institution, the University of Cambridge, in partnership with NHSBT.

Why is the study needed?

Because shortages in the blood supply are projected for England, NHSBT is exploring different approaches to ensure adequate blood supplies for the future.

One way to increase the blood supply is to ask blood donors to give blood more frequently. However, some time is required between blood donations to allow the body to replace its iron stores.

Because no one knows what is the optimum interval between donations, blood donation services in different countries have developed varying customs. In England, NHSBT invites men to donate every 12 weeks and women to donate every 16 weeks. By comparison, some European countries invite people to donate blood as frequently as every 8 weeks.

The INTERVAL study aims to recruit about 25,000 men and about 25,000 women from NHSBT blood donation centres across England. If you choose to join this study, you will take part for a period of two years. During this time we will invite you to give blood either at your usual donation interval or more frequently. Men will be invited to donate every 8, 10 or 12 weeks and women every 12, 14 or 16 weeks. The donation interval you are allocated to will be decided by a process called ‘randomisation’, which is like a coin toss. As usual, you will be able to give blood only if you pass the screening haemoglobin finger-prick test.

At the end of the study, we will compare the amount of blood donated and measures of well-being in people asked to give blood at standard intervals versus those asked to give blood more frequently.

To find out whether certain people have capacity to give blood more frequently, we will be collecting an additional small blood sample at the beginning and end of the study to look at iron levels and DNA for relevant genes. Not all of the blood sample will be used immediately and some will be stored so that it can be used to assist future studies about the health of blood donors.

Main Results

Have there been other publications from INTERVAL and where can I find them?

Yes, publications are found at Publications include those relating to:

i) Analysis of INTERVAL data and samples to answer the trial’s main questions about optimum donation intervals
ii) Results of other studies that INTERVAL participants have been involved in
iii) Findings of research involving the use of samples and data collected during the INTERVAL trial looking at donor and public health-related questions.

I was told I had low haemoglobin/iron levels during the study, how often should I be donating?

NHSBT’s routine health screening procedures assess whether your haemoglobin levels are safe for you to donate. If you do not pass these tests then you will be deferred for a given period of time.

The study shows that while some donors could donate more frequently than the current donation intervals, other donors should donate at longer intervals. These findings will allow greater personalisation of blood donation. In the future, some donors may give blood more often, and some less depending on specific characteristics.

If donors wish to discuss the finding of the research with someone who should they contact?

Please send an email to letting them know the nature of your query and they will refer it to the relevant person to provide you with a response.

If there are changes to recommendations on donation frequency, will I have to donate more often?

No, you can decide to donate at a frequency that suits you.

What do the findings of the study show?

The study showed that, over 2 years, the majority of donors could give blood more frequently without having a major impact on their health. Information on how different people can give blood safely could boost the supply of blood to the NHS. More details on the study’s findings is found here.

Will I be asked to be involved anything further for the INTERVAL study?

The INTERVAL research team or NHS Blood and Transplant may ask if you would like to help with other studies to help with blood donation or other important public health questions. You can decide if you want to help or not. Your decision will not affect your blood donation now or in the future. Other research which INTERVAL participants have been involved in after the INTERVAL trial include:

  • NIHR BioResource: This is funded by the Department of Health to help understand what causes important conditions such as cardiovascular disease and diabetes. The BioResource recruits healthy volunteers and participants who agree to be invited in the future to participate in ethics-approved research studies. Over 12,000 INTERVAL participants have joined NIHR BioResource.
  • INFORM: A subset of INTERVAL participants was invited to the University of Cambridge-led INFORM study. We considered if providing people with different types of information about their individual risk of a heart attack would help them change their lifestyle (for example to eat a healthier diet, exercise more or stop smoking). Publications relating to the INFORM trial can be found here.
  • CARRIAGE: Small numbers of INTERVAL participants were asked to help with a study of bacteria carried in the nose. Donors took nasal swabs to help researchers identify who did and didn’t carry the bacterium Staphylococcus aureus (S. aureus). This is important, as carriers are at much greater risk of all types of S. aureus infections. Further information about the study can be found here.
Will I now be able to donate more often?

No, not at the moment. The new research may change the official recommendations on donation. For now, the intervals between blood donations will stay the same (every 12 weeks for men and every 16 weeks for women).

It will take some time to translate the findings of the INTERVAL study into routine donation practice. In particular, NHS Blood and Transplant will need to understand which type of donors can safely donate more often without an adverse impact on their iron stores.

Will there be any other changes to the donation service based on the study’s results?

The results from the trial suggest that we need better screening methods to measure haemoglobin levels in potential donors. A further study (COMPARE) is now looking at how different tests can spot donors who meet or fall below the haemoglobin threshold for donation ( This study, in almost 30,000 donors, is now completed and we are looking at the results. NHS Blood and Transplant will use the results to decide on the best screening method in the future.

Will there be further publications about the INTERVAL study?

Yes. There will be many more publications relating to the INTERVAL trial including the results of:

  1. INTERVAL Phase II where some donors gave blood at their study-allocated donation frequency for a period of up to 4 years
  2. INTERVAL Phase III in which some donors provided a series of research samples across 2 or more donations
  3. Research looking at whether increasing donation frequency is a cost-effective way of increasing the supply of blood.
Will you be able to tell me the results from measurement in my blood samples?

During the 2-year INTERVAL study, we collected research samples when you joined and at your 2-year anniversary. We measured fresh blood samples and froze some of your blood for future tests. We measured your full blood count and if any results could have an immediate impact on your healthcare (such as a low haemoglobin level or high platelet count), we will have told you.

It is not planned to feedback any further results as these are research results and not designed for clinical tests.

Phase II

Do I automatically become part of Phase II?

No. To join Phase II you must click the link in the invitation email that we send you and fill out the online consent form.

How long do I have to decide whether to join Phase II?

You have 21 days to complete the online consent form starting from the date that you receive our email invitation to join Phase II. If you lose the email we can resend it, but only within the 21 day consenting period. If you are in any doubt please call the Helpline on 0800 064 0089.

How long is Phase II?

Phase II will finish in June 2016.

I am deferred from donating blood, can I join?

Yes. If you are deferred from donating blood you are able to continue to make an important contribution to the study’s findings. If you are able to give blood again during your participation in Phase II, we will ask you to do so at your previously allocated donation interval.

I don’t want to consent online, can you send me a copy in the post?

I’m afraid not. Due to practical considerations, the consenting process has been designed to be completed online only.

I’d like to help your research but I don’t want to keep donating at my assigned study interval.

That is fine, if you decide not to join INTERVAL Phase II you can still help us with our future research. You can do this by giving the INTERVAL researchers permission to retrieve, in the long-term, study-specific anonymised data from your donor record. These data will be used by the study investigators to gain more information on the effect of donation frequency on blood supply and donor well-being. There is an option to consent to this level of involvement in our research within the online information for Phase II.

I’m a platelet donor, but I’m still on the INTERVAL study, can I join?

No, I’m afraid not. But we would like to thank you for your help with our research so far and your valuable contributions to the donation service.

What happens immediately after I enrol in the study?

A few days after enrolling we will send you a welcome email which will include contact details for your future appointments and for any further questions you have about the study.

What should I do if I want to take part?

You will be sent an email invitation with a link to an online information sheet and consent form. Depending what stage you have reached in the 2-year INTERVAL study, you may receive this email either several weeks before or shortly after your final study donation before your 2-year anniversary. If you decide to join the study after reading the online information, all you need to do is complete our online consent form.

What standards are in place to protect me and the data / samples I provide?

INTERVAL Phase II will maintain the standards that have been in place during the first phase of INTERVAL to protect you and your data. This includes regular review by an independent safety committee.

What will be involved?

If you choose to join INTERVAL Phase II, you will:

  • Continue to give blood at one of the 24 fixed Donor Centres across England
  • Attend your donation appointments, until June 2016, at your previously allocated study interval, i.e. 8, 10, or 12 weeks for men and 12, 14, or 16 weeks for women
  • Make your appointments through the INTERVAL Study Administration Team (ISAT). You won’t be able to make your appointments through NHSBT’s National Call Centre, Donor Portal or Website
  • Receive reminders about your donation appointments by either an approach very similar to that used during the first phase of INTERVAL or an approach which involves less frequent reminders
  • The type of reminders you receive will be decided by an entirely random process
  • Continue to complete questionnaires every 6 months until June 2016

You may also be asked to:

  • Give a small research blood sample at the end of the study
What’s happened so far on INTERVAL?

The INTERVAL trial was set up as a 2-year study to assess the impact of shorter donation intervals on the health and well-being of blood donors and on blood services. In the last two years, 50,000 donors have been recruited into the study. This remarkable achievement is thanks to donors like you who have supported this research.

Who do I contact if I have any further questions or concerns?

If you have any more questions or concerns about INTERVAL Phase II please contact the Helpdesk on 0800 064 0089 or email


Why is Phase II happening now?

The last participant was recruited in mid-June 2014. The reason for Phase II is to make maximum scientific use of the time between now and June 2016, when the last participants recruited into INTERVAL are due to end their 2-year involvement in the study. We are now inviting interval participants, like you, to keep donating blood until June 2016 at the same interval you have been assigned to give blood as part of the INTERVAL study.

Why is Phase II needed?

Rather than stopping your involvement at your 2-year anniversary of joining INTERVAL, we would like you to consider getting involved in INTERVAL Phase II in order to provide extra valuable information to help us develop strategies to enhance the health of blood donors and optimise blood services.

Phase II will enhance the information we have already planned to collect during the 2-year INTERVAL study. In particular, this extension period will enable researchers to work out if donors find it acceptable to donate more or less often beyond a duration of two years. It will also evaluate the impact of different donation frequencies on the health and well-being of donors and on blood services over this longer period. The Phase II extension will provide an opportunity to tackle an additional question: what is the impact on donors’ health and on blood services of a more active approach to managing appointments for blood donations? In INTERVAL, the approach has been somewhat “more active” than the approach routinely used by NHS Blood and Transplant. For example, INTERVAL has provided donors with more frequent reminders to attend appointments than is routine in the blood service. However, the impact of using these different approaches is not known. So, to compare these approaches directly in a rigorous manner, we will randomly allocate donors who join INTERVAL Phase II to receive reminders about their donation appointments by either an approach very similar to that used during the first phase of INTERVAL, or an approach which involves less frequent reminders through NHSBT’s routine reminder system.

Will I know which type of appointment reminders I have been randomised to?

No. It is possible that you may get reminders about your appointments as you previously did on INTERVAL (i.e. through ISAT) or through NHSBT’s reminder systems.

Phase III

I don’t want to consent online, can you send me a copy in the post?

Unfortunately, no. Due to practical considerations, the consenting process has been designed to be completed online only.

INTERVAL Phase III – why have I been invited?

We want to recruit about 4,000 INTERVAL participants to INTERVAL Phase III. We are inviting donors who:

  • Do not have an existing donation deferral at the time of joining Phase III
  • Have enough time remaining on the study to give a minimum of 2 consecutive research samples at their allocated donation frequency

To take part, it is important that you i) have no known reasons (e.g. extended holidays) which will prevent you from giving blood between the time of your invite and your last donation as part of the INTERVAL study, and ii) are willing to give a small, research sample at each donation attended as part of the INTERVAL study.

INTERVAL Phase III – why now?

INTERVAL Phase III has emerged out of a growing interest, among blood donation services and researchers, in factors that influence the recovery of iron stores following repeated donation. The INTERVAL study provides an ideal opportunity to explore these factors – especially as it will be possible to look at patterns of iron recovery at different donation frequencies.

What happens immediately after I enroll in the study?

A few days after enrolling we will send you a welcome email which will include contact details for your future appointments and for any further questions you have about the study.

What should I do if I want to take part?

If you are eligible to join, you will receive an email invite from the INTERVAL study team – this will contain a web-link to Phase III study information and an online consent form. If you would like to join INTERVAL Phase III then all you need to do is complete the online consent form and give your consent.

What standards are in place to protect me and the samples I provide?

Phase III will maintain the same standards to protect you and your data and samples that were set out at the time of you enrolment to the study.

What will be involved?

If you choose to join INTERVAL Phase III the following will happen:

  • A flag will be placed on your donor record indicating to staff at your Donor Centre that you are happy to provide a small research blood samples at each of your next donations attended as part of the INTERVAL study.
  • If you meet NHSBT’s usual criteria for blood donation when you attend an appointment you will be able to give your routine blood donation plus your research blood samples.
  • If you do not meet NHSBT’s usual criteria for blood donation when you attend an appointment, a research blood sample only will be taken.
  • The INTERVAL study team will send reminders, similar to those you are already receiving, to remind you to book and/or attend study donation appointments when they are due.
Who do I contact if I have any further questions or concerns?

If you have any more questions or concerns about INTERVAL Phase III please contact the Helpdesk on 0800 064 0089 or email

Physical Activity

Can I take the activity monitor with me when I go on holiday?

Yes. You can put the monitor on your wrist and forget about it. It is also safe to pass through airport security. But please do not forget to return it to us after the date given in the enclosed letter when you get home.

Can I wear the monitor for longer than the date given in the enclosed letter?

The monitor turns off automatically after the date given in the enclosed letter. Please return it to us as soon as possible after that date in the stamped addressed FREEPOST envelope provided.

Do I need to take it off for certain activities?

The device is robust and water-proof, and has been designed to be worn when working or sleeping, having a bath or shower, or playing all types of sport, including swimming. Extremes of temperature may damage the battery though, so it should be taken off if you have a sauna.

How do I return the activity monitor?

Please post the device back to us as soon as possible after the date given in the enclosed letter. All you need to do is put it into the stamped addressed padded envelope provided, seal the envelope and put it in a post box. The cost of postage is already paid.

How long do I have to wear it?

Please put it on as soon as it arrives and wear it continuously until the date given in the enclosed letter.

How secure is the information on the monitor; suppose it gets lost in the mail?

The activity monitor does not contain any information that can identify you. A special code number on each device is matched with your “participant ID number”, and the key to this code is known by the INTERVAL study data manager only. Your personal details and data about your health and lifestyle are stored separately. Other security mechanisms are also used to protect your privacy.

How will I know if it is working?

The activity monitor is set up to turn itself on and off automatically. As it is completely silent, you will not be able to tell that it is running.

I was away for a few days when the monitor arrived. Is it still worth wearing?

Yes, provided it is still before the return date given in the letter. If it is after that date, please return the device to us with a note to say that you were unable to wear it. Unfortunately we will not be able to replace it with a new one.

My job does not allow me to wear accessories: can I still take part?

Yes. Please remove the activity monitor if you are required to do so for work, but don’t forget to
put it back on again afterwards.

On which wrist should I wear it?

It is preferable to wear the monitor on the wrist of the hand that you would use to throw a ball. But, if this is not possible for some reason then please wear it on the other wrist.

What does the activity monitor measure?

The activity monitor records information about the duration, frequency and intensity of all kinds of activity (from sleeping to vigorous physical activity). It does this by measuring acceleration in three directions (up/down; forwards/backwards; and left/right). Scientists will be able to determine how active a person has been based on the information collected by the activity

What if I have to take off the monitor?

If you need to take the monitor off for some reason please put it in a stationary place, e.g. in a drawer, not in your bag, and then put it back on as soon as you can.

What is the monitor made of, and might it cause an allergic reaction on my wrist?

The activity monitor is made of moulded thermoplastic and the strap is hypoallergenic. A mild reaction, e.g. itchiness, may be experienced if you have an allergic reaction to plasters, but there are no other risks associated with wearing the activity monitor.

What should I do if I cannot find the return envelope?

Don’t worry. You can return the activity monitor to us in a padded envelope using our FREEPOST address:

INTERVAL Study Strangeways Research Laboratory
Wort’s Causeway

What should I do if I lose the activity monitor or it breaks?

Don’t worry. If the device breaks just return it to us in the envelope provided. We are able to retrieve any information that has already been collected. If you lose the device please let us know by telephoning free of charge 0800 064 0089 (Mon-Fri; 9:00am-5:00pm).