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

Abstract

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.

Keywords: Cancer; Cardiovascular; Cohort study; Fracture; Postmenopausal women.

Figure 1.

(A) Women diagnosed at the same time for: cardiovascular and fracture (n = 9), cardiovascular and diabetes (n = 3), cardiovascular and cancer (n = 4), and cancer and fractures (n = 3). (B) Women diagnosed at same time for: cardiovascular and fracture (n = 4), cardiovascular and diabetes (n = 2), cardiovascular and cancer (n = 2), cancer and fractures (n = 1), and cancer and fracture (n = 1). (C) Women who died at the time of the first event (n = 1 430) or after (n = 4 855) without experiencing a second event. (D) Women who died at the time of the second event (n = 841) or after (n = 2 107) experiencing a second event.

Figure 2.

Results (hazard ratios [HRs] and 95% confidence intervals [CIs]) for individual healthy lifestyle index components derived from Cox regression models adjusted for age, total nonalcohol energy daily intake, race, education, family income, marital status, clinical trial participation, history of hormone replacement therapy, insomnia, and hypertension at baseline. AHEI = Alternative Healthy Eating Index; cig = cigarettes; kg = kilogram; m = meter; MET/wk = metabolic equivalent hours per week.

Figure 3.

The 25-year cumulative incidence functions of multimorbidity by quintiles of healthy lifestyle index and lifetable failure events by follow-up interval time (5 years). Quintiles of healthy lifestyle index. All models were adjusted for age, education, income, ethnicity/race, participation in Women’s Health Initiative clinical trials, enrollment in the calcium and vitamin D intervention trial, enrollment in the dietary intervention arm, enrollment in the menopausal hormone therapy trial, ever use of menopausal hormone therapy, years since menopausal occurred, total energy intake, insomnia, and history of high blood pressure. (A) Risk of developing a second morbidity after a diagnosis of cardiovascular disease. Model accounting for competing risk of having cancer, diabetes, fracture as first event, or death. (B) Risk of developing a second morbidity after a diagnosis of cancer. Model accounting for competing risk of having cardiovascular disease, diabetes, fracture as first event, or death. (C) Risk of developing a second morbidity after diabetes. Model accounting for competing risk of having cancer, cardiovascular disease, fracture as first event, or death. (D) Risk of developing a second morbidity after a fracture. Model accounting for competing risk of having cardiovascular disease, diabetes, cancer as first event, or death. ^*p Value for the tests of equality of cumulative functions.