Association between five lifestyle habits and cancer risk: results from the E3N cohort.

Although some modifiable lifestyle characteristics have been associated with decreased cancer risk, little is known about their combined effect or about the proportion of cancer cases that could be prevented by improving lifestyle behaviors. We aimed to quantify the association between lifestyle habits and all-site and site-specific cancer risk in middle-aged women. The study included 64,732 women from the French E3N prospective cohort, ages 43 to 68 years at baseline. During a 15-year follow-up period, 6,938 cases of invasive cancer were diagnosed. We defined an index that aggregated five lifestyle characteristics: smoking, body mass index, alcohol consumption, fruit and vegetable consumption, and physical activity. Proportional hazard Cox regressions were performed to evaluate the association between lifestyle and cancer risk and to estimate multivariate HRs and their 95% confidence intervals (CI). In addition, population-attributable fractions were used to estimate the proportion of cancer cases that could be prevented by healthier behaviors. A significant decrease in all-site cancer risk was observed and was associated with a healthy lifestyle (HR, 0.81; 95% CI, 0.73-0.89 when comparing the highest with the lowest health index category; Ptrend across categories < 0.01). Combining all five characteristics would have prevented 6.3% (2.2%-10.3%) of any-site, 6.3% (0.5%-12.1%) of postmenopausal breast, and 47.5% (26.8%-64.1%) of lung cancers. In conclusion, compliance with only five modifiable lifestyle behaviors could prevent a significant number of cancers, notably postmenopausal breast and lung cancers.