Obesity Fills In for Smoking as Major Killer

Obesity is a central factor in mortality among women who have never smoked, especially those in lower social classes, researchers reported.

Class differences in who smokes have been shown to increase social inequalities in all-cause mortality, according to Carole Hart, PhD, of the University of Glasgow in Glasgow, Scotland, and colleagues.

But in a long-running cohort study among women who had never smoked, obesity stepped up to the plate as a cause of inequalities in mortality, Hart and colleagues reported online in BMJ.

The finding comes from a large cohort study started in the 1970s in the neighboring Scottish towns of Paisley and Renfrew, which enrolled more than 15,400 people ages 45 through 64 at the time.

As might be expected, people who had never smoked had much better survival rates than smokers, regardless of their social position, and women who had never smoked had the best survival rates in the cohort, Hart and colleagues reported.

But after 28 years of follow-up, they noted, age-adjusted survival rates for women who had never smoked were 65% in the highest occupational class and 56% for those in the lowest, suggesting some other factors were creating social inequalities in the risk of death.

To clarify the issue, they analyzed outcomes for 3,613 women who had never smoked, stratifying them by occupation and by body mass index.

Occupationally, the women were placed into four groups – professionals and managers, nonmanual skilled occupations such as office workers, manual skilled occupations such as bricklayers, and semi- and unskilled workers.

Those in lower occupational groups, the researchers found, were shorter and had poorer lung function, higher systolic blood pressure, and a higher body mass index than women in higher classes. All the trends were significant at P<0.001, they reported.

Overall, 43% of the women were overweight, 14% were moderately obese, and 5% severely obese, Hart and colleagues reported, and obesity rates were higher in lower occupational classes.

As well, overweight and obesity was much higher – regardless of social class – among the nonsmokers than among the women in the full cohort who smoked.

For instance, among the professionals and managers, 40.3% of never-smokers were overweight, compared with 29% among the smokers in the same occupational group.

The finding suggests a masking effect of smoking, the researchers noted.

Over the 28 years of follow-up, Hart and colleagues reported, 1,796 of the 3,613 never-smokers died, with 51% of deaths due to cardiovascular disease and 27% owing to cancer (table 3).

Overall, 39% of the professionals and managers died, as well as 47% of the nonmanual skilled workers, 56% of manual skilled workers, and 54% of the semi- and unskilled workers.