In George Orwell’s Animal Farm, first published in 1945, some animals were “more equal than others”. In 2009 the human situation is similar both in the UK and worldwide. Social inequality leads to health inequality in terms of disease causation, treatment and health outcomes [1]. There is growing momentum at governmental and global level to target the so-called social determinants of ill health, which include social gradient, occupation and social support networks [1]. Smoking is the single greatest risk factor for mortality in later life and since people in lower socioeconomic groups are more likely to smoke, they are more likely to have ill health [1,2]. This week’s BMJ reports the first ever long-term study to compare smokers and non-smokers in both sexes, across the whole social spectrum. The study population was based in western Scotland and consisted of 8000 women and 7000 men, followed up over 28 years, starting from 1972 [3]. Social class was measured by occupation and social deprivation, based on the subject’s postcode. There are three new findings. Firstly, “smokers in all social classes have poorer survival than those who never smoked in even the lowest social positions”. In women, comparing never-smokers and current smokers, survival rates were 65% vs. 41% in the highest class and 56% vs. 35% in the lowest class. In men, comparing never-smokers and current smokers, survival rates were 53% vs. 24% in the highest class and 36% vs. 19% in the lowest class. Secondly, the mortality of ex-smokers was much closer to never-smokers than current smokers. Thirdly, women of the same social class and smoking history have higher survival rates than their male counterparts, but smoking by women “seems to nullify the survival advantage they otherwise have over men”. Previous analyses from both UK [4] and from global data [5] have suggested that the majority of health inequalities between socioeconomic groups (as much as 85%) are attributable to smoking which is confirmed by this new data. Smoking reduces the survival advantage of women and the higher social classes, and so it is an equaliser in one sense. Smoking rates and the associated mortality are still high, with men smoking more cigarettes than women and only 46% of women and 17% of men classified as “never-smokers” [3], and so there is great scope for action. This compelling new evidence suggests that the best way to reduce health inequalities is to reduce smoking rates in people of lower social position. Programmes focusing solely on social determinants of health are likely to be unsuccessful in addressing these health inequalities.

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1. Commission on Social Inequalities in Health. Achieving health equity: from root causes to fair outcomes. Geneva: World Health Organization, 2007.
2. Doll R, Peto R. Boreham J, Sutherland I. Mortality in relation to smoking: 50 years observations on male British doctors. BMJ 2004;328:1519-33.
3. Gruer L, Hart CL, Gordon DS, Watt GCM. Effect of tobacco smoking on survival of men and women by social position: a 28 year cohort study. BMJ 2009; 338: b480.
4. Law M, Morris J. Why is mortality higher in poorer areas and in more northern areas in England and Wales? J Epidemiol Community Health 1998;52:344-52.
5. Ezzati M, Lopez AD. Potential health gains from reducing multiple risk factors In:  Ezzati M,  Lopez AD,  Rodgers A,  Murray CJL, eds. Comparative quantification of health risks: global and regional burden of disease attributable to selected major risk factors. Geneva: World Health Organization, 2004.