Adherence to a low-risk, healthy lifestyle and risk of sudden cardiac death among women

Abstract

Context: Sudden cardiac death (SCD) accounts for more than half of all cardiac deaths; the majority of SCD events occur as the first manifestation of heart disease, especially among women. Primary preventive strategies are needed to reduce SCD incidence.

Objective: To estimate the degree to which adherence to a healthy lifestyle may lower the risk of SCD among women.

Design, setting, and participants: A prospective cohort study of 81,722 US women in the Nurses' Health Study from June 1984 to June 2010. Lifestyle factors were assessed via questionnaires every 2 to 4 years. A low-risk lifestyle was defined as not smoking, body mass index of less than 25, exercise duration of 30 minutes/day or longer, and top 40% of the alternate Mediterranean diet score, which emphasizes high intake of vegetables, fruits, nuts, legumes, whole grains, and fish and moderate intake of alcohol.

Main outcome measure: Sudden cardiac death (defined as death occurring within 1 hour after symptom onset without evidence of circulatory collapse).

Results: There were 321 cases of SCD during 26 years of follow-up. Women were a mean age of 72 years at the time of the SCD event. All 4 low-risk lifestyle factors were significantly and independently associated with a lower risk of SCD. The absolute risks of SCD were 22 cases/100,000 person-years among women with 0 low-risk factors, 17 cases/100,000 person-years with 1 low-risk factor, 18 cases/100,000 person-years with 2 low-risk factors, 13 cases/100,000 person-years with 3 low-risk factors, and 16 cases/100,000 person-years with 4 low-risk factors. Compared with women with 0 low-risk factors, the multivariable relative risk of SCD was 0.54 (95% confidence interval [CI], 0.34-0.86) for women with 1 low-risk factor, 0.41 (95% CI, 0.25-0.65) for 2 low-risk factors, 0.33 (95% CI, 0.20-0.54) for 3 low-risk factors, and 0.08 (95% CI, 0.03-0.23) for 4 low-risk factors. The proportion of SCD attributable to smoking, inactivity, overweight, and poor diet was 81% (95% CI, 52%-93%). Among women without clinically diagnosed coronary heart disease, the percentage of population attributable risk was 79% (95% CI, 40%-93%).

Conclusion: Adherence to a low-risk lifestyle is associated with a low risk of SCD.

Figure 1

Relative risks and 95%CI for sudden cardiac death by the binary lifestyle score. Low risk was defined as not currently smoking, exercise at moderate to vigorous intensity ≥30 min/day, diet in the top 40% of the Alternate Mediterranean Diet Score (aMed) distribution and BMI <25 kg/m². The relative risks are estimated from Cox proportional hazards models adjusted for age (months), family history of MI (no, <60 years, 60+ years), menopausal status (yes / no), current hormone therapy (yes/no), and presence of diabetes, hypertension, high cholesterol, cancer, coronary heart disease and stroke at baseline (all yes/no). Age, menopausal status and current hormone therapy were treated as time-varying covariates.