For Nonsmoking Women, Obesity Is a Killer
While smoking is remains the leading preventable cause of death, obesity is gaining ground. A new study published online in the British Medical Journal notes that obesity is an important contributor to premature death in women who have never smoked, especially among women in low income groups.
Obesity is known to be a major risk factor for cardiovascular disease, certain types of cancer, and type 2 diabetes. Over the past 30 years, obesity in the United States has risen. According to the CDC, in 2009 more than 33 states had a prevalence of obesity equal to or greater than 25%.
Dr Laurence Gruer from NHS Health Scotland and colleagues chose to look at what could happen to health inequalities if smoking were eliminated as a risk factor.
Gruer and colleagues reviewed the cases of 3,613 women from Scotland who had never smoked. These women participated in a study of over 15,000 adults who were recruited to the Renfrew and Paisley Study in 1972-1976 when aged 45-64 and have been followed up until death.
The study participants were grouped by occupational class (I and II, III non-manual, III manual, and IV and V) and by weight (normal weight, overweight, moderately obese and severely obese).
Overall, 43% (n=1555) of the study participants were overweight, 14% (n=515) moderately obese, and 5% (n=194) severely obese.
During the follow-up period of 28 years, half the women died, including 916 (51%) from diseases of the heart and circulation and 487 (27%) from cancer.
The researchers found that women who had never smoked and were not obese had the lowest mortality rates, regardless of their social position.
Women in lower occupational classes who had never smoked were found on average to have higher systolic blood pressure than women in the higher occupational classes. These women were more likely to die of diseases of the heart and circulation rather than cancer. They were also more likely to be severely obese and those who were severely obese had the highest death rates.
Never-smoked, obesity rates were higher in lower occupational classes and much higher in all occupational classes than in current smokers in the full study cohort. The authors feel this suggests that high smoking rates 35 years ago probably concealed the true extent of obesity in non-smoking women and that the decline in smoking rates in recent decades may have contributed to the increase in overweight and obesity.
Dr Gruer argues that the results have important implications. Although lifelong smoking is clearly responsible for much higher mortality rates, obesity, and especially severe obesity, has probably been an important contributor to premature mortality in populations like this for some time. He adds that where obesity is more common in disadvantaged groups it may contribute to health inequalities and increase the burden on local health and social services.
On a positive note, the authors conclude that women who never smoke and are not obese have relatively low mortality rates regardless of their social position.
In the accompanying editorial, Professor Johan Mackenbach from the Erasmus Medical Center Rotterdam, says the study is welcome "but it is important not to forget that smoking is a much stronger risk factor for mortality than most other risk factors, including obesity."
He concludes that "inequalities in mortality persist among those who have never smoked, partly because obesity takes over the role of smoking, but they persist at a much lower level, and that is good news for whoever wants to reduce health inequalities."
C. L. Hart, L. Gruer, G. C. M. Watt. Cause specific mortality, social position, and obesity among women who had never smoked: 28 year cohort study. BMJ, 2011; 342 (jun28 1): d3785 DOI: 10.1136/bmj.d3785