Association Between the Healthy Lifestyle Index and Risk of Multimorbidity in the Women’s Health Initiative

Background: Multimorbidity, defined as the presence of 2 or more chronic health conditions, is increasingly common among older adults. The combination of lifestyle characteristics such as diet quality, smoking status, alcohol intake, physical activity (PA), sleep duration, and body fat as assessed by body mass index (BMI) or waist circumference, and risk of multimorbidity are not well understood. Objectives: We investigated the association between the healthy lifestyle index (HLI), generated by combining indicators of diet quality, smoking, alcohol, PA, sleep amount, and BMI, and risk of multimorbidity, a composite outcome that included cardiovascular disease (CVD), diabetes, cancer, and fracture. Methods: We studied 62 037 postmenopausal women aged 50–79 years at enrollment in the Women’s Health Initiative, with no reported history of CVD, diabetes, cancer, or fracture at baseline. Lifestyle characteristics measured at baseline were categorized and a score (0–4) was assigned to each category. The combined HLI (0–24) was grouped into quintiles, with higher quintiles indicating a healthier lifestyle. Multivariable adjusted estimates of hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the risk of developing multimorbidity were obtained using Cox proportional hazard models. Results: Over an average follow-up period of 16.3 years, 5 656 women developed multimorbidity. There was an inverse association between the HLI levels and risk of multimorbidity (compared to the HLI_1st quintile: HR_2nd quintile = 0.81 95% CI 0.74–0.83, HR_3rd quintile = 0.77 95% CI 0.71–0.83, HR_4th quintile = 0.70 95% CI 0.64–0.76, and HR_5th quintile = 0.60 95% CI 0.54–0.66; p trend < .001). Similar associations were observed after stratification by age or BMI categories. Conclusions: Among postmenopausal women, higher levels of the HLI were associated with a reduced risk of developing multimorbidity.