1. MRC/CSO Social and Public Health Sciences Unit Socioeconomic gradients in coronary heart disease - the relative role of lifestyle Linsay Gray 1, Julie Armstrong 2, Yvonne Brogan 2, Andrea Sherriff 3, Catherine Bromley 4, Alastair H Leyland 1 1 MRC/CSO Social and Public Health Sciences Unit, Glasgow, UK 2 School of Life Sciences, Glasgow Caledonian University, Glasgow, UK 3 Department of Dentistry and Medicine, University of Glasgow, Glasgow, UK 4 Scottish Centre for Social Research, Edinburgh, UK Royal Statistical Society Edinburgh local group talk, 15 November 2011

2. MRC/CSO Social and Public Health Sciences Unit Background CHD strongly correlated with SES Lifestyle factors impact on health and are also linked with SES Thus may drive the CHD-SES associations Individual and combined lifestyle contributions to such inequalities not well quantified

3. MRC/CSO Social and Public Health Sciences Unit Aims To quantify contributions of lifestyle factors to social inequalities in CHD Individual and combined

4. MRC/CSO Social and Public Health Sciences Unit Data 6,060 participants >16 years in 2003 Scottish Health Survey (60% response) providing data on also consenting to linkage of mortality and hospital records ‘til 2008 SES (social class) Smoking status (current and previous) Physical activity levels Diet (quality index) next slide BMI and Alcohol consumption (weekly intake) CHD death or admission

5. MRC/CSO Social and Public Health Sciences Unit Diet quality index - DQI >20 foods Summary measure scores based on recommendations types and frequency Fish, red meat and products Starchy foods High fibre foods Sugary foods Fatty foods Fruit and vegetables (Alcohol) Armstrong, J. et al. (2009).

6. MRC/CSO Social and Public Health Sciences Unit Statistical methods Cox proportional hazards regression 1: Ascertain prediction of CHD event by SES adjusting for age only 2: Investigate degree of attenuation of the association of CHD with SES by lifestyle Assess using Relative Index of Inequality (RII)

7. MRC/CSO Social and Public Health Sciences Unit Relative Index of Inequality (RII) Commonly used measure of extent to which occurrence of an outcome - such as CHD - varies with risk factors such as SES Measures relative disparity by summarizing relative risk for extremes Calculation Rank values Scale ranks from 0 to 1 Analyse as a covariate in usual way Obtain estimates for a “one unit increase”

8. MRC/CSO Social and Public Health Sciences Unit CHD and baseline social class data 35,523 person-years of follow-up 213/6,060 (4%) CHD events; including 59 (28%) deaths;

9. MRC/CSO Social and Public Health Sciences Unit Lifestyle factors MeanSD Dietary quality index 52 17 BMI27 kg/m 2 5.3 kg/m 2 Alcohol units/week14 units 21 units

10. MRC/CSO Social and Public Health Sciences Unit Alcohol distribution

11. MRC/CSO Social and Public Health Sciences Unit Natural log of alcohol distribution

12. MRC/CSO Social and Public Health Sciences Unit Lifestyle factor associations with SES and CHD SESCHD Smoking status all p<0.001 Never Ex-occ 0.287 Ex-reg<0.001 Current 0.003 Physical activity Low Medium <0.001 High<0.001 Dietary quality index 0.50 BMI0.011 ln(Alcohol units/week)0.004

13. MRC/CSO Social and Public Health Sciences Unit Number breakdown Social classdeathsn Professional 9442 Intermediate 561937 Skilled (non-manual) 21880 Skilled (manual) 711554 Partly Skilled 38905 Unskilled 18342 All 2136060

14. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results

15. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results

16. MRC/CSO Social and Public Health Sciences Unit Proportional hazards? - log-log plot

17. MRC/CSO Social and Public Health Sciences Unit Proportional hazards check

18. MRC/CSO Social and Public Health Sciences Unit Proportional hazards check p=0.539

19. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results Social classdeathsn HR95% CI Non-manual 863,1731.00 Manual 1272,6741.601.212.10 RII 2136,0602.101.293.43 Sex interaction p = 0.254

20. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results - attenuation by smoking % Social classdeathsn HR95% CI HR95% CIdecrease Non-manual 863,1731.00 Manual 1272,6741.601.212.101.461.111.9322 RII 2136,0602.101.293.431.771.072.9031

21. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results - attenuation by physical activity % Social classdeathsn HR95% CI HR95% CIdecrease Non-manual 863,1731.00 Manual 1272,6741.601.212.101.531.162.0211 RII 2136,0602.101.293.431.931.183.1615

22. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results - attenuation by diet % Social classdeathsn HR95% CI HR95% CIdecrease Non-manual 863,1731.00 Manual 1272,6741.601.212.101.531.162.0310 RII 2136,0602.101.293.431.951.183.2114

23. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results - attenuation by BMI % Social classdeathsn HR95% CI HR95% CIdecrease Non-manual 863,1731.00 Manual 1272,6741.601.212.101.571.202.074 RII 2136,0602.101.293.432.041.243.336

24. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results - attenuation by alcohol % Social classdeathsn HR95% CI HR95% CIdecrease Non-manual 863,1731.00 Manual 1272,6741.601.212.101.591.212.091 RII 2136,0602.101.293.432.081.273.402

25. MRC/CSO Social and Public Health Sciences Unit CHD and social class Cox regression results - attenuation by all lifestyle factors % Social classdeathsn HR95% CI HR95% CIdecrease Non-manual 863,1731.00 Manual 1272,6741.601.212.101.371.031.8237 RII 2136,0602.101.293.431.530.922.5652

26. MRC/CSO Social and Public Health Sciences Unit Strengths and limitations Reasonable sample size Covers the (home-dwelling) general population of Scotland High linkage consent (>90%) Range of covariates Emigration – lost to follow-up but low levels Excludes those living in communal establishments e.g. prisons residential care Bias from survey response (67% household; 60% individual)

27. MRC/CSO Social and Public Health Sciences Unit Conclusions Adjusting for lifestyle factors attenuates association by over 50% Individually, greatest impacts made by smoking (31%), physical activity (15%) and diet (14%) Little impact of BMI and alcohol Valuable insight for tackling socio-economic health inequalities Importance of physical activity and healthy eating as well as smoking What else? Structural/environmental factors

28. MRC/CSO Social and Public Health Sciences Unit Acknowledgements Data were provided by ISD Funding was provided by the Chief Scientist Office for Scotland Thanks to Joan Corbett of ScotCen for help with data queries

29. MRC/CSO Social and Public Health Sciences Unit Thank you for your attention Contact me on l.gray@sphsu.mrc.ac.uk for further informationl.gray@sphsu.mrc.ac.uk