The Scottish Health Survey 2008

INTRODUCTION

Catherine Bromley

OVERVIEW OF THE 2008 SCOTTISH HEALTH SURVEY

The 2008 Scottish Health Survey was commissioned by the Scottish Government Health Directorates. It is the fourth of a series of surveys aimed at monitoring health in Scotland. During 2005 and 2006 a comprehensive review of the survey was carried out by the then Scottish Executive ¹. One of the key recommendations to emerge from the review was that the survey should be carried out on a more frequent basis. This recommendation was adopted and the survey began running continuously in 2008 with a contract let for the four years from 2008 - 2011. This report is based on data collected in the first year of its new format, 2008. Future reports will present findings from additional years as well analysis carried out using a pooled dataset drawn from more than one year.

The previous three surveys took place in 1995, ² 1998, ³ and 2003 ⁴ and were conducted by the Joint Health Surveys Unit ( JHSU) of the National Centre for Social Research (NatCen) and the Department of Epidemiology and Public Health at University College London ( UCL). In 2003, the JHSU collaborated with the MRC Social and Public Health Sciences Unit based in Glasgow ( MRCSPHSU). The 2008-11 surveys are being conducted by a collaboration between the Scottish Centre for Social Research (part of NatCen), the MRCSPHSU and UCL.

Each survey in the series consists of main questions and measurements (for example, anthropometric and, if applicable, blood pressure measurements and analysis of blood and saliva samples), plus modules of questions on specific health conditions. As with the earlier surveys in the series, the principal focus of the 2008 survey was cardiovascular disease ( CVD) and related risk factors. The main components of CVD are coronary heart disease ( CHD) and stroke. As noted in Chapter 8, CHD is Scotland's second biggest cause of death and is the focus of a significant number of health policies, many of which have a specific emphasis on reducing the significant health inequalities associated with CVD in Scotland. The SHeS series means that there are now trend data going back for over a decade, and providing the time series is an important function of the survey.

Many of the key CVD risk factors are in themselves of particular interest to health policy makers and the NHS. For example, smoking, poor diet, lack of physical activity, obesity and alcohol misuse are all the subject of specific strategies targeted at improving the nation's health. The Scottish Health Survey includes detailed measures of all these factors.

The Survey consists of two stages, all those sampled are invited to take part in the first stage interview while a sub-sample is invited to also complete a second stage visit from a nurse. The interview includes questions on general health, mental health, cardiovascular disease, respiratory symptoms, eating habits, smoking, drinking, and physical activity, as well as height and weight measurements. There are additional modules asked only in certain years (for example, extended CVD and respiratory questions, and on accidents), and a module about knowledge and attitudes to health which is asked of a sub-sample of adults in every year on behalf of NHS Health Scotland. ⁵ The nurse visit collects additional information and takes further measurements including blood pressure, lung function, saliva and blood samples, and a urine sample. See Volume 2 of this Report for a more detailed discussion of the survey's methodology and design, including the changes to the design that were implemented as a result of the survey's review in 2005/6.

Sample design

The sample has been designed to cover the four year period 2008-11 and has been designed to provide data at both national and regional level about the population living in private households in Scotland. Each single year of the survey has been designed to provide estimates at the national level. The survey used a multi-stage stratified probability sampling design, with data zones (or groups of data zones) selected at the first stage and addresses (delivery points) at the second. The three previous survey samples (1995, 1998 and 2003) were designed to ensure that the sample size was sufficiently large within seven regions based on aggregations of Health Boards for the purpose of regional analysis. The 2008-11 sample design has been changed and will instead be able to provide sufficient samples within each Health Board area after four years for the purpose of regional analysis. ⁶

Two samples were selected for the survey: a general population (main) sample in which all adults and up to two children were eligible to be selected in each household; and a child boost sample in which up to two children were eligible to be selected in additional households in the same datazones.

The sample of addresses was selected from the small user Postcode Address File ( PAF). This is a list of nearly all the residential addresses in Scotland and is maintained by The Royal Mail. The population surveyed was therefore people living in private households in Scotland. People living in institutions, who are likely to be older and, on average, in poorer health than those in private households, were not covered. This should be considered when interpreting the survey estimates. The very small proportion of households living at addresses not on PAF (less than 1%) was not covered.

Fieldwork

Fieldwork for the 2008 survey started in January 2008, and continued through to March 2009. Fieldwork for the second year of the survey started in January 2009. Each sampled address was sent a letter explaining the survey in advance of the first interviewer visit. Interviewing was conducted using Computer Assisted Personal Interviewing ( CAPI). Children aged 13-15 were interviewed in the presence of a parent or guardian. Parents answered on behalf of younger children, who were nevertheless required to be present. In addition, those aged 13 and over were asked to complete a short paper questionnaire on more sensitive topics. There were four such booklets: one for adults aged 18 and over, one for young adults aged 16-17 (with the option of using it for those aged 18-19 at the interviewer's discretion), and one for teenagers aged 13-15. Parents of any children aged 4-12 years, included in the sample, were also asked to fill in a self completion booklet about the child's strengths and difficulties designed to detect behavioural, emotional and relationship difficulties in children.

Interviewers were also responsible for measuring participants' height and weight. Finally, in a sub-sample of households, they sought permission for a follow-up visit by a specially trained survey nurse.

At the nurse visit, participants were asked about their use of prescribed medication and recent experiences of food poisoning and stress, anxiety and depression. The nurse then took the blood pressure and waist and hip measurements for all aged 16 and over, and measured the arm length (demi-span) for those aged 65 and over. Lung function was measured via a spirometer. With written agreement, a small sample of blood was taken by venepuncture. The blood sample was analysed for: total and HDL-cholesterol, c-reactive protein, fibrinogen and glycated haemoglobin. Nurses also sought agreement for the storage of a small sample of blood for possible future analysis. Samples of saliva and urine were also collected. Further details of these samples and measurements are available in the Glossary.

Survey response

There were 6,465 individual interviews with adults and 1,750 with children aged 0-15. This includes 1,239 children interviewed in the main sample, and 511 interviewed in the boost sample. 1,878 adults were eligible to take part in the nurse visit, and of these 1,123 saw a nurse and 903 gave a blood sample.

In the main sample, 61% of eligible households (4,139) took part in the 2008 survey. 49% of adults in participating households were interviewed. In the child boost sample, 64% of eligible households (345) co-operated with the survey, and in all but four of these households, all eligible children were interviewed.

Data

The data collected in the field was subjected to an intensive editing process to produce a fully 'clean' final dataset. This covered coding of verbatim responses, including 'other' responses to pre-coded questions, as well as a series of consistency and plausibility checks on data values.

Since addresses and individuals did not all have equal chances of selection, the data have to be weighted for analysis. The Scottish Health Survey 2008 comprised a general population (main sample) and a boost sample of children screened from additional addresses. Therefore slightly different weighting strategies were required for the adult sample (aged 16 or older) and the child sample (aged 0-15). These are describe in full in Volume 2.

The 2008 Scottish Health Survey data will be deposited at the Data Archive at the University of Essex, from where the 1995, 1998 and 2003 datasets may also be obtained.

This report

The 2008 Scottish Health Survey report consists of two volumes, published as a set as 'The Scottish Health Survey 2008'. Volume 1 presents results for adults for the topics listed below. Chapter 7 also includes the results of children's healthy weight, an important national indicator. Volume 2 provides methodological information and survey documentation. These two volumes are available on the Scottish Government's Scottish Health Survey website ( www.scotland.gov.uk/scottishhealthsurvey).

1. General health and mental wellbeing
2. Dental health
3. Alcohol
4. Smoking
5. Fruit and vegetable consumption
6. Physical activity
7. Obesity
8. Cardiovascular disease and diabetes

Data for men and women are presented separately, in some instances figures for the whole adult population are cited in the text. The same is true for boys and girls. Survey variables are tabulated by age groups and, usually, Scottish Index of Multiple Deprivation ( SIMD), National Statistics Socio-Economic Classification ( NS-SEC), and equivalised household income. Trend data are presented, where possible, from the four surveys in the Scottish Health Survey series (1995, 1998, 2003 and 2008). In some cases trend data are restricted to those aged 16-64 (the age range common to all four surveys), for some measures trends are available for the 16-74 age range (common to the 1998 survey onwards). Trends based only on the 2003 and 2008 surveys can be presented for all adults.