Adherence to a low-risk, healthy lifestyle and risk of sudden cardiac death among women.
Level 3 - non-randomized controlled study
Prospective observational cohort study with 26 years of follow-up.
PubMed 21730242 · doi:10.1001/jama.2011.907
What was done
A prospective cohort study followed 81,722 US women enrolled in the Nurses' Health Study from June 1984 to June 2010 (26 years). Lifestyle variables were assessed via questionnaires every 2 to 4 years. A low-risk lifestyle was defined by four factors: not smoking, body mass index < 25, physical activity ≥ 30 minutes/day, and high adherence (top 40%) to an alternate Mediterranean diet. The primary outcome was sudden cardiac death (SCD), defined as death within 1 hour of symptom onset without prior circulatory collapse.
What was found
During follow-up, 321 SCD events occurred (mean age at event: 72 years). Absolute risk was 22 cases/100,000 person-years among women with 0 low-risk factors, 17 for 1 factor, 18 for 2 factors, 13 for 3 factors, and 16 for 4 factors. Compared with women with 0 low-risk factors, multivariable relative risks for SCD were 0.54 (95% CI, 0.34–0.86) for 1 factor, 0.41 (95% CI, 0.25–0.65) for 2 factors, 0.33 (95% CI, 0.20–0.54) for 3 factors, and 0.08 (95% CI, 0.03–0.23) for all 4 factors. The population attributable risk proportion for smoking, physical inactivity, overweight, and poor diet was 81% (95% CI, 52%–93%) overall, and 79% (95% CI, 40%–93%) among women without diagnosed coronary heart disease.
Why it matters
Because sudden cardiac death frequently presents as the first clinical manifestation of heart disease in women, primary prevention through combined conventional lifestyle modifications may prevent a substantial majority of SCD events.
Limits
The observational design cannot establish causality and remains susceptible to residual confounding. Lifestyle exposures were self-reported via periodic questionnaires, introducing potential misclassification bias. The cohort consisted exclusively of female US registered nurses, potentially limiting generalizability to men, other occupational groups, and broader racial or socioeconomic populations.
Cited by
- contradicts Half of all heart attacks result in sudden death.