Impact of lifestyle in middle-aged women on mortality: evidence from the Royal College of General Practitioners' Oral Contraception Study.

BACKGROUND: Although many individuals have multiple lifestyle risk factors, few studies have investigated the impact of lifestyle risk factor combinations among women.

AIM: To investigate the relationship between individual and combinations of lifestyle risk factors in middle-aged women with subsequent mortality, and to estimate the associated population attributable risks.

DESIGN OF STUDY: Prospective cohort study.

SETTING: Royal College of General Practitioners' (RCGP) Oral Contraception Study, UK.

METHOD: In 1994-1995, women remaining under follow-up in the RCGP Oral Contraception Study were sent a lifestyle survey, from which modifiable risk factors were identified: pack-years smoked, physical inactivity, never drinking versus consuming at least 7 units of alcohol weekly, and being underweight, overweight, or obese. The cohort was followed to December 2006 or death. Population attributable risks were calculated.

RESULTS: Of 10 059 women studied, 896 died. Pack-years smoked (11-20 years: adjusted hazard ratio [HR] = 1.82, 95% confidence interval [CI] = 1.46 to 2.27; >20 years: adjusted HR = 2.34, 95% CI = 2.00 to 2.74); never drinking alcohol (adjusted HR = 1.66, 95% CI = 1.34 to 2.05); being underweight (adjusted = HR 1.66, 95% CI = 1.03 to 2.68); and physical inactivity (<15 hours/week: adjusted HR = 1.73, 95% CI = 1.46 to 2.04) were significantly associated with mortality compared with their respective reference group. Women with multiple lifestyle risk factors had higher mortality risks than those reporting one factor. The population attributable risk of the combination of smoking, physical inactivity, body mass index outside normal range, and alcohol (never drinking or excess intake) was 59% (95% CI = 31% to 78%).

CONCLUSION: Assuming a causal relationship between lifestyle and mortality, avoidance of four lifestyle risk factors would have prevented 60% of the deaths. The importance of avoiding smoking and undertaking physical inactivity during midlife should continue to be emphasised.