Survey of Health, Ageing and Retirment in Europe (SHARE)

The current ratio of older people to total population in Europe is higher than
on any other continent * yet, the phenomenon of population aging will continue
well into this century everywhere on this planet. The Survey of Health, Ageing
and Retirement in Europe (SHARE, please visit our website www.share-project.org
for further information), which started data collection in 2004, is the first
study to examine the different ways in which people aged 50 and older live in
twenty countries from Scandinavia to the Mediterranean.

SHARE is a cross-national and multidisciplinary panel study incorporating
individual self-reported information regarding social, economic and health
factors as well as national institutional and social policy conditions in order
to understand how we age differently within Europe. These factors are
well-known determinants of healthy ageing in its broad definition which
includes adequate economic and social support as well as good health.

Self-reported information on health is important as it reflects subjective
impressions. When collected in different countries, however, it is typically
biased because individual perceptions vary across countries as much as
socio-cultural factors. This bias can be overcome through objective measures of
biological and physical functions, so-called biomarkers. For this reason,
biomarkers, serving as indicators of the objective state of health, are
increasingly used in epidemiological and socio-economic research.

Already from its beginning, SHARE has used objective physical biomarkers
well-known for their prediction of adverse health outcomes, e.g. grip strength
and lung force. But even though these physical biomarkers provide some valuable
insights about potential health risks, they can only give us indirect
information and do not allow us to understand the underlying processes and
pathways. This knowledge gap can be filled with the aid of biological
biomarkers. Although there is still much to learn in this field, we already
know some biological biomarkers that are strongly correlated with health. And
the field is expanding.

In many clinical and epidemiological studies, biomarkers have been collected
through venipuncture and venous blood analyses. Such a methodology is extremely
expensive when used in field surveys such as SHARE. As an alternative, the
method of Dried Blood Spot (DBS) sampling has been introduced to the research
field. DBS sampling means that several drops of blood are taken by pricking,
e.g. a finger, and collecting the capillary blood drops on a filter-paper card.
The blood spots are left to dry and the cards are then shipped by ordinary
postal mail to a laboratory, where they are stored in freezers until analyses
are performed. DBS samples can easily be collected in surveys employing trained
lay interviewers.

Present biotechnology allows DBS samples to be used to determine various
lipoprotein or protein structures as well as tracer elements (e.g. heavy
metals) in the individual. Among them, the more well-known biological markers,
like glycated hemoglobin (HbA1c), a marker of diabetes, and C-reactive protein
(CRP) and cytokines, markers of inflammation and associated with
atherosclerosis, hypertension and cardiovascular diseases, have reliably been
measured in DBS samples. More recently, DBS assays for the measurement of
Vitamin D and cholesterol have been developed and validated. Low values of
Vitamin D are associated with a loss of muscle mass, muscle weakness and
functional decline, as well as elevated risk of osteoporosis and fracture.
Cholesterol is a marker for the risk of cardiovascular diseases. DBS assays for
other biomarkers are still under development and will have huge potentials in
future studies.

The biomarkers collected in SHARE are expected to give novel insights into the
relations between chronic conditions common in old age and behavioural and
environmental risk factors under various socio-economic conditions. The
inclusion of DBS sample collection in SHARE will therefore not only enrich the
SHARE database but also support multidisciplinary scientific research.
Moreover, we are certain that the results from the collection of biomarkers in
SHARE will have a profound influence on public health policy for the benefit of
individuals in Europe and elsewhere.

Including the collection of biological biomarkers into a social survey such as
SHARE is of important scientific value as it opens up multiple research
possibilities:
-Identification of causal relationships: biological biomarkers can help to
understand the complex relationships between social status and health and their
physiological pathways.
-Pre-clinical information: biomarkers allow to identify pre-disease pathways,
since the physiological processes are often below the individual*s threshold of
perception.
-Measurement of respondents* health can be improved: Standard health questions
in surveys are often subject to the respondents* own interpretation (of the
question), own evaluation or perception (of health status), and own knowledge
(of health status) and health literacy. The value of subjective health
measurements is undeniable, but some research questions require objective
measurements. Especially in international comparisons self-reported health data
may be biased by varying country-typical response styles. Biomarkers enable
researchers to validate respondents* self-reports and therefore to study the
amount and determinants of under-, over-, and misreporting in large-scale
population surveys.

A fundamental advantage of including the collection of biomarkers into a
large-scale survey such as SHARE is the simultaneous availability of biological
and socio-demographic data in a representative (i.e. non-clinical) population.
Using these data, manifold research areas can be investigated, e.g. the
implications of recent public policy interventions on the health of older
citizens, the causal link between biological aging processes with socially and
economically induced health behaviours, or the future costs of typical chronic
diseases in old age, such as diabetes.

In general, we are interested in biomarkers indicating the development of
diseases that occur typically from onwards the mid of live (such as
cardiovascular diseases) and conditions which are influenced by life style and
environmental factors. In particular, the following parameters from the
collected DBS samples will be analysed:
-Glycated hemoglobin (HbA1c): this is a measure for identifying the blood sugar
concentration over a longer period of time. We are not measuring the current
blood sugar level (NOT fasting blood sugar, thus respondents are allowed to eat
or drink before taking the blood spots); instead, by analysing the HbA1c value
from the blood spot, we find out about the average blood sugar level of the
last 2-3 months, and if somebody might have diabetes or not. Diabetes is a
common disease of old age and of unhealthy lifestyle. Furthermore, if diabetes
is known to the respondent, the HbA1c value tells, how well the respondent is
adjusted to the treatment.
-Vitamin D (Vit. D): low values of Vit. D are associated with a loss of muscle
mass, muscle weakness and functional decline, as well as elevated risk of
fracture (osteoporosis). Vit. D blood concentration is highly dependent on
nutrition and sunlight exposure. As the latter depends on local climate and
latitude, and the former on nutrition habits that differ regionally, comparing
vitamin D levels in a cross-national survey may provide interesting insights in
the risk of developing diseases according to where somebody lives.
-Total cholesterol: The level of total cholesterol is a good marker for the
risk of developing cardiovascular diseases. These diseases often have a subtle
beginning below the threshold of the person*s perception. The analyses of the
total cholesterol can help to identify patients in an early stadium of
cardiovascular diseases which would otherwise pass unobserved.
-C-reactive protein (CRP) and cytokines (such as TNF*, IL-6, BDNF): CRP and
cytokines are inflammation markers which tell us if a respondent has an ongoing
inflammation. Subdued but non-disease specific increases of CRP/cytokines are
correlated with cardiovascular diseases and stress. Also ageing per se is
associated with cytokine release, but at much lower levels than the elevations
observed during infections. A wide range of environmental factors (e.g.
smoking, infections, and obesity), genetic factors, and declining functions of
sex hormones contribute to this systemic low-grade inflammatory activity in
older individuals, but also age-associated diseases contribute. Both Tumor
Necrosis Factor alpha (TNF-*) and Interleukin 6 (IL-6) have been associated
with morbidity and mortality and are believed to reflect the underlying
pathogeneses of atherosclerosis, diabetes and dementia, as well as frailty and
functional decline. Many other cytokines relevant to ageing exist, e.g.
Brain-Derived Neurotrophic Factor (BDNF), which is released from nerve cells
during exercise and activates the brain stem cells to convert into new neurons
as well as protecting existing neurons from degradation. Accordingly BDNF has
been linked to dementia and depression. Lifestyle factors may affect negatively
(smoking, obesity) or positively (diet, physical activity) the level of
circulating cytokines. Furthermore, low socio-economic status has been linked
to elevated inflammatory markers.

These data therefore allow the investigation of the correlation between
socio-economic conditions and behaviour and the risk of developing certain
diseases, which all are an immense economical factor for the ageing European
society.

SHARE is a multidisciplinary and cross-national panel database of micro data on
health, socio-economic status and social and family networks of more than
85,000 individuals (approximately 150,000 interviews) from 19 European
countries (+Israel) aged 50 and over.

1. Sample size and target population

The target population for inference from SHARE is the European population aged
50 and over. For practical reasons the definition of the study population for
SHARE is: Persons born in 1964 or earlier, and persons who are a spouse/partner
of a person born in 1964 or earlier, who speak the official language(s) of the
country and who are residents within private households, regardless of
nationality and citizenship.

To achieve representation of this population, SHARE employs a sample design
which involves baseline samples of the household population aged 50 and over at
a particular point in time in each country, supplemented by regular refreshment
samples of the sub-population of people who have turned 50 since the original
baseline sample was selected.

The sample size in the Netherlands will be 4000 individuals. We will ask panel
respondents as well as refresher respondents, who do an interview for the first
time, to participate in the dried blood spot collection. The participation in
this part of the interview is voluntary. Should a respondent refuse to have
blood spots taken, no blood will be collected. Furthermore, we will not collect
blood in case the interview is a proxy-interview (i.e. an interview not with
the originally sampled person but with another person who knows him/her well)
or if the respondent is not able to understand the information given to him/her
prior to the DBS sample collection and/or to agree to the collection of blood
spots.

2. Methodology (Dried Blood Spot Sampling)

SHARE is a face-to-face interview that takes place in the respondents' homes
using CAPI (Computer-Assisted Personal Interviewing) software. In the middle of
the interview the collection of DBS samples is conducted. Of course, the
participation is absolutely voluntary (with regard to the SHARE study as well
as regarding the collection of the DBS samples). All participating respondents
will be asked for their (informed and written) consent to have their blood
collected for DBS samples.

DBS samples are collected by taking blood from a finger prick using a small,
sterile lancet * just as it is done daily by millions of diabetic people. After
pricking a fingertip with the small lancet, a few drops of blood are dripped on
specified (circled) areas of a card made of filter paper, i.e. a DBS filter
card. The card is registered by a unique identifier in the format of a barcode
printed on a sticker attached to the card and the respective barcode number is
typed into the CAPI by the interviewer. When dry, the filter card is put into a
special tear-proof and water-resistant envelope. As DBS samples are sensitive
to moisture and high temperatures, a small desiccant bag and a temperature
sensitive strip are added to the envelope before being dispatched by postal
mail to the SHARE Biobank located at the Institute of Public Health, University
of Southern Denmark in Odense, Denmark.

At the beginning of the DBS sample collection each respondent is given an
information leaflet (and enough time to read it), then he/she has to sign a
consent form. The signed consent form is collected by the interviewer and sent
to the the survey agency, while a copy of the form is left with the respondent.
Both forms have the respondents' unique barcode attached.

3. Materials Needed & Blood Sample Collection

The following materials are needed in order to collect the DBS samples:
- 2 Blood spots collecting cards
- Disposable protective cloth
- 2 pairs of disposable rubber gloves
- Disposable disinfecting wipes
- 2 semi-automatic lancets
- Cotton balls
- Plasters
- Desiccant
- Small plastic bag for blood spot collecting card
- Small envelope for blood spot collecting card
- Special, water-resistant and tear-proof mailing envelope
- Barcode stickers
- Address stickers
- Temperature sensitive strip
- 2 copies of the "Dried Blood Spots Collection" consent form
- Large plastic bag for waste material
The detailed steps of the DBS sampling are the following:
1. The respondent is asked to give informed and written consent to participate
in the DBS collection, if yes
2. The respondent is asked to rub and/or shake hands (warm hands ensure enough
bleeding through good capillary circulation).
3. All parts from the blood collection kit are placed on the disposable
protective cloth.
4. The blood spot collecting cards, consent forms and envelopes are marked with
individual barcodes.
5. The interviewer puts on rubber gloves.
6. The finger to be pricked (preferably the respondent*s fourth finger on the
non-dominant hand) is cleaned with the disinfecting wipe and let to dry.
7. The semi-automatic lancet is activated on a lateral side of the respondent*s
finger and blood drops are collected (the puncture can be done either by the
interviewer or by the respondent himself):
8. Using a cotton ball, the first drop of blood is wiped off.
9. The next large drops of blood from the respondent*s finger are allowed to
drop onto the pre-marked circles of the DBS filter card (without touching them
with the fingers).
10. The respondent is provided with a cotton ball and a plaster to attach
firmly to the puncture site which is observed for continued bleeding (in case
of which a second plaster is provided and the finger should be held firmly in
an elevated position).
11. The barcode number is entered into the CAPI (double-checked).
12. The card is put aside to dry until the end of the whole SHARE interview,
but for 15 minutes minimum.
13. Used materials are discarded.
14. The dried DBS filter card is posted in a special tear-proof and
water-resistant envelope for biological material together with a desiccant and
a temperature sensitive strip.
15. The DBS sample should be sent to the SHARE Biobank as soon as possible
after the interview using the standard mail service. Meanwhile the samples
have to be kept in a cool place.


4. Processing and Storage of the DBS Samples

To ensure comparability of the biomarker analysing results, all DBS samples
from all SHARE countries are sent to one single biobank, namely the SHARE
Biobank at the Institute of Public Health of the University of Southern Denmark
in Odense.

Upon arrival at the biobank, the DBS sample is immediately processed, given
arrival on a weekday. The process starts by scanning the barcode on the DBS
filter card and, thus, registering the sample in a specific SHARE biomarker
database together with the dates of the sample collection, the mailing stamp
and the arrival at the biobank. The indicated temperature on the temperature
sensitive strip * showing the highest temperature the sample was exposed to *
is entered into the database as well. Once registered in the database, copies
of the unique barcode are printed on stickers for later use (see below).

To minimise the risk of accidental events jeopardising the quality of the
sample or resulting in a later loss of the DBS sample, the DBS card is divided
into three subsamples, each registered in the database by the same unique
barcode number and marked with a barcode sticker, and put in a new envelope,
which is sealed inside a plastic bag containing a desiccant. Each of the three
subsamples is finally stored in different freezers and their exact locations
are also registered in the database. The temperature of the freezers is kept at
-20°C. Experiences from the National Danish Biobank in Copenhagen show that the
biological material on the DBS cards can be kept frozen at this temperature for
many years without significant deterioration. An alarm will sound in case the
temperatures of the freezers deviate significantly from -20°C and a biobank
staff member on call will receive a warning by mobile phone.

To ensure confidentiality, the barcode is the only "identifier" of the
individual respondent. Neither the biobank nor the processing laboratory have
access or connection to the SHARE interview database and do not keep any names
or other personal information in their database. After the mentioned analyses
have been carried out, the DBS samples will still be kept in the biobank. The
respondents consent to their blood samples being stored after the ending or
termination of the DBS collection in SHARE. But they may revoke their
participation and request the removal from storage and the destruction of their
blood samples at any time.

5. Analyses and Linkage oft the Results to the SHARE Dataset

The DBS samples collected in SHARE wave 6 will be used to carry out analyses
regarding the development of diseases, which occur often from onwards the mid
of life in order to enable scientific research to conduct comparative analyses
of correlations between such diseases and life circumstances (such as family,
occupation, retirement, social networks). At this, the main focus lies on
cardiovascular diseases and diseases, which are influenced by life style and
environmental factors. In particular the following pre-specified analyses will
be conducted: Glycated hemoglobin (HbA1c), Vitamin D (Vit. D), total
cholesterol, C-reactive protein (CRP) and the cytokines tumor necrosis
factor-alpha (TNF-*), interleukin 6 (IL-6), brain-derived neurotrophic factor
(BDNF).

In this context participants are given the opportunity to exclude certain
analyses from being done. This, of course, also applies with regard to analyses
related to scientific research questions in the above mentioned research areas,
which could be answered with the help of the DBS samples in the future. Since
other biological biomarkers are still under development and will have huge
potentials with regard to future scientific research, the samples will be
stored in the SHARE Biobank even after the pre-specified analyses have been
conducted in order to maintain the possibility to carry out further scientific
analyses in this field.

Finally, for scientific research purposes all the analyses results are sent to
the central SHARE coordination team where the data are merged with the SHARE
wave 6 database. Since the unique barcode number was entered into the CAPI
during the interview, the DBS analyses results can be linked to the interview
data. However * to emphasise this * the barcode numbers will not be part of any
of the releases in the SHARE database used by scientific researchers.

Dried blood spots (DBS) sampling is safe and easy to perform. The method of DBS
sampling was developed to safely gain a small blood sample from a newborn to
check for a disabling metabolic disease (phenyl ketonuria), which may be
avoided if disclosed right after birth. In the last years, the method was
adapted to field surveys taking blood from adult respondents to generate
objective health data. In Sweden, self-administered DBS collection is used in
diabetes control monitoring of patients living in more remote areas. In
population-based ageing research in Denmark, more than 3500 DBS samples have
been collected among the old and oldest old without any problems. Also in
Germany during SHARE wave 4, more than 1400 DBS samples have been collected,
and no problems occurred. Pricking the finger is in general associated with
very low risks. Millions of diabetic people do it daily to check their blood
glucose. The puncture can cause light pain or a small hematoma.