Physical activity moderates the association between nicotine dependence and depression among U.S. smokers

Purpose: Research demonstrates that nicotine dependence and depression are associated and that physical activity is effective in reducing depression symptoms. However, our understanding of the potential beneficial effects of physical activity on depression in current smokers is more limited. The purpose of this study was to examine whether physical activity moderates the association between nicotine dependence and depression in U.S. smokers.

Design: Cross-sectional.

Setting: National Health and Nutrition Examination Survey 2005-2006.

Subjects: Four hundred forty-one current adult smokers.

Measures: Participants wore an accelerometer for at least 4 days and completed questionnaires to assess nicotine dependence and depression.

Analysis: Effect modification and statistical interaction models were used.

Results: Both models were significant. With regard to the statistical interaction model, and after controlling for age, gender, race/ethnicity, education, comorbidity index, homocysteine, cotinine, total cholesterol, sedentary behavior, and vitamins C, D, and E, objectively measured physical activity moderated the association between nicotine dependence and depression (interaction variable: odds ratio = 3.43; 95% confidence interval: 1.02-11.51; p = .04).

Conclusion: In this national sample of current smokers, physical activity moderated the association between nicotine dependence and depression. These results suggest that those individuals with nicotine dependence and who are less physically active are more likely to be depressed than what would be expected on the basis of the individual effects of nicotine and physical inactivity separately.