1. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Quantifying non-response bias in the Scottish Health Surveys by comparison of alcohol-related harms with the general population Gorman E 1, Leyland AH 1, McCartney G 2, White IR 3, Katikireddi SV 1,4, Rutherford L 5, Graham L 6, Gray L 1 1 MRC/CSO SPHSU, University of Glasgow 2 NHS Health Scotland 3 MRC Biostatistics Unit 4 Department of Public Health and Policy, NHS Lothian 5 Scotcen Social Research 6 ISD, NHS National Services Scotland 6th EUROPEAN PUBLIC HEALTH CONFERENCE 13-16 November 2013 Brussels, Belgium

2. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Background National health surveys play a vital role in shaping public health policy Many surveys are facing declining response levels Potential for bias * Tolonen, Hanna, et al. "25-year trends and socio-demographic differences in response rates: Finnish adult health behaviour survey." European Journal of Epidemiology 21.6 (2006): 409-415.

3. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Motivations Non-respondents tend to be in poorer health compared with respondents o Greater hospitalisation rates o Elevated risk of psychiatric and mental disorders o More likely to be hazardous drinkers Post-survey corrections (weighting/MI) typically based on limited information, eg age, sex, region A lack of health-related data may limit our ability to adjust for health-related differences.

4. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Measuring alcohol consumption Survey estimated alcohol consumption: o Mis-reporting o Recall bias o Non-response bias? Substantial under- estimation of population alcohol consumption * Beeston C, et al., Monitoring and Evaluating Scotland’s Alcohol Strategy. 2 nd Annual Report. Edinburgh. NHS Health Scotland 2012.

5. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Response levels and alcohol consumption Response levels and alcohol consumption estimates in men in the Scottish Health Surveys, retail-based consumption estimates and population male alcohol-related mortality in Scotland 1995-2011 * Gray L, McCartney G, White IR, SV Katikireddi, L Rutherford, E Gorman, AH Leyland. Use of record-linkage to handle non- response and improve alcohol consumption estimates in health survey data: a study protocol. BMJOpen 2013 ; 3:e002647

6. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Research question: Are rates of alcohol-related harm in the Scottish Health Survey respondents equivalent to those in the general population?

7. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Denominator data SCOTTISH HEALTH SURVEYS Repeated cross-sectional surveys designed to measure the health of the Scottish population living in private households 1995, 1998, 2003, 2008, 2009 and 2010 Household response proportion: 81%-63% GENERAL POPULATION Census-derived mid-year population estimates 96% enumeration All available by age-group, sex, area-deprivation quintile and geographical area of residence

8. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Numerator data SCOTTISH MORBIDITY AND MORTALITY RECORDS Anonymised alcohol-related hospital and death records drawn from routinely-collected national records (1981-2011) o Demographic, socio-economic and clinical information o Both general and mental health admissions SHeS Hospital and death records are confidentially linked at an individual level with consenting Scottish Health Survey respondents (consent proportion 91%-86%) General population Hospital and death records are combined with population denominator data by age-group, sex, area- deprivation quintile and geographical area of residence.

9. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Methods Rates of alcohol-related harm were compared between each survey and the corresponding general population data - o Outcome is time to hospitalisation or death due to alcohol o Hospital and death records allow follow-up from baseline year until end of 2011: maximum of 16 years from 1995 o Restricted to those aged 20 to 64 years at baseline survey year (1995, 1998, 2003, 2008, 2009 or 2010) o Rates were calculated for survey respondents and the general population, by sex, and directly age-standardised to the European Standard Population.

10. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Results Rates of subsequent alcohol-related harm are lower in the SHeS respondents compared with the general population MalesFemales

11. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Conclusions and implications Under-representation of those with high risk of alcohol- related harm may suggest associated under-estimation of aggregate alcohol consumption due to non-response Alcohol-related health outcomes are associated with non-response and should be incorporated into post- survey adjustments (weighting, MI) Increased understanding of health-related differences between respondents and non-respondents will inform further work to generate refined survey estimates of key health behaviours.

12. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Discussion Key strength is in the use of robust routinely-collected administrative records o Record-linkage allows direct comparison between survey respondents and general population Bias from non-consent to linkage? Differential sampling frame between surveys and population - o The SHeS, as with many household surveys, is limited to private households o Institutionalised population <2%; but likely to experience relatively high rate of harm.

13. MRC/CSO Social and Public Health Sciences Unit, University of Glasgow. Acknowledgements Data were provide by the Information Services Division, Scotland and the Scottish Government (SG) Funding was provided by the MRC Methodology Research Panel grant [MR/J013498/1]. Project advisors: Julie Ramsay, SG; Clare Beeston, NHS Health Scotland; Jim Sherval, NHS Lothian; and Michaela Benzeval, University of Essex Protocol paper: Gray L, McCartney G, White IR, SV Katikireddi, L Rutherford, E Gorman, AH Leyland. Use of record-linkage to handle non-response and improve alcohol consumption estimates in health survey data: a study protocol. BMJOpen 2013;3:e002647