Summary of study methods

This article will summarize the following issues:
1 Outcome measures
2 Study procedures

1 Outcome measures
a. The development of a disease related to ageing, metabolic and endocrine diseases, cardiovascular, renal, pulmonary or musculoskeletal disorders, and psychopathology.
b. The burden of disease for society in terms of care needed and costs of care.
2 Study procedures
Inclusion of participants

The prospective participants in the study are approached by a letter from their GP, and a folder with basic information on the study (attachment 1 and 2). Added to this letter is a reply form (attachment 3) which future participants can fill in and return toll-free to the Lifelines organization if they want to participate or, if they do not want to participate, with the reasons for not participating. On this reply form they also can specify their preferences regarding times and days of the week for the first study visit (also available through Internet). Persons willing to participate receive a more detailed folder with information on the study, an informed consent form, a questionnaire (part 1 which can also be entered through a secured internet site) and a date and time for the first study appointment (attachment 5,6,7). The cover letter explicitly states that people can refuse to participate without affecting the care by their GP or the University Medical Centre Groningen (attachment 4). The questionnaire has to be filled in (on paper or online) before the first visit, and, if on paper, returned at the first visit. There is a minimum of two weeks between the first and second letter. In case, no reply form is returned, the relevant prospective participants will receive a reminder (attachment 9). In case a participant misses a visit a no show letter will sent (attachment 10 ).

Participants will be asked if their partners, parents, and parents in law would like to participate in the study and if so, permission will be asked to send them information (attachment 11). These persons will be informed and invited for participation by the LifeLines organisation (attachment 1b, 1c). Family relations will be registered in a family database. From each relative that is known to the LifeLines organisation, the name, LifeLines code and willingness to participate will be recorded.

Intake visits to General Practitioner or Research Site During the first visit the signed informed consent is taken in. If requested, additional information will be provided.

During the first and second visit, the first or second part of the questionnaire, respectively, are taken in and checked for completeness, a number of investigations are conducted and blood and urine samples are taken (see below). The second visit is scheduled approximately 2 weeks after the first visit, depending on available time and preference of the participant. For participants of 65 years and older, a MMSE (minimal mental state examination) will be conducted in order to determine the capabilities of the participant. An adapted program or visits at home by the research nurse will be conducted; a decision to do so is at the discretion of the participating general practitioner. In principle, the adapted program will identical to the standard program instead that the questionnaires will be divided in several parts. Additionally, for all participants, investigations will not be performed when the participant is physically or mentally not capable in the performance of one or more specific investigations, a decision to do so is at the discretion of the research nurse.

Also, data relevant for the study (medication, hospital admissions, medical investigations performed, and diagnoses) are retrieved from the general practitioners’ records. A specific application is developed that secures that only relevant data are extracted, only after proper coding. If this is not possible, data verification of important medical events will be done based on reports of specific health care providers.

• Questionnaires
The participant is asked to fill the questionnaire in at home (on paper or online), and to return the paper versions by mail or to deliver it at the first scheduled visit. If there are problems filling in the questionnaire, LifeLines personnel can be contacted for assistance.
The baseline questionnaire consists of the following parts:
-Demographics
-Family composition
-Work and educational level
-Health
-Questions for females
-Birth and development
-Lifestyle and diet
-Day time spending
-Living environment
-Quality of life
-Health perception
-Personality
-Stress
-Social support

• The Investigational schedule of the first visit is as follows:
1. Signed informed consent is taken in
2. All possible questions, which a participant may have in relation to his or her participation, are discussed by the research nurse
3. Anthropometric measures: height, weight, hip and waist circumference
4. Blood pressure: using a DINAMAP, measurements during 10 minutes
5. 12-lead electrocardiogram (ECG)
6. Pulmonary function tests (FEV1 and VC)
7. Ruffs Figure Fluency Test (RFFT): test of cognitive function
8. MINI interview: neuropsychiatric interview in which a number of basic questions are asked about fears and depression
9. The containers for the 24-hour urine collection are handed out including instructions
10. The container for the first morning urine is handed out together with instructions
11. Questionnaire part 1 is taken in and checked for completeness
12. Questionnaire part 2 is handed out
13. Family form is handed out

• Investigational schedule second visit:
1. Fasting venapuncture, 75 ml blood is collected. Full blood count, renal function, electrolytes, liver tests, total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, glucose and HbA1c as well as hsCRP, apo B100 and apo A1 are measured directly to detect subclinical abnormalities.
2. Measurement of skin autofluorescence with a non-invasive AGE-reader (Advanced Glycation Endproducts).
3. 24 hour urine is handed in, in order to measure the following: albumin, total amount per 24 hours of sodium, potassium, calcium and phosphate.
4. First morning urine is taken in, in order to measure the albumin/kreatinin ratio.
5. Questionnaire part 2 to be taken in and checked on completeness.
6. Family form to be handed in.
All measurements are described in procedures and performed by trained Lifelines personnel, i.c. research nurses.
Follow-up procedures
Yearly, the participants will receive a questionnaire.
The yearly questionnaire consists of the following parts:
-Change of address / change in family members
-Incidence of diseases / visits to health care providers
-Medication use
-Additional information on health determinants, e.g. nutrition

Every 4-5 years participants are invited for a visit to the general practitioner or research site. These follow-up visits include blood sampling, urine collection and measurements like the baseline measurements. A questionnaire comparable to the baseline questionnaire is used. Maximal efforts will be used to have follow-up examinations in most participants.