Impact of Healthy Lifestyle Factors on Life Expectancies in the US Population

Abstract

Background: Americans have a shorter life expectancy compared with residents of almost all other high-income countries. We aim to estimate the impact of lifestyle factors on premature mortality and life expectancy in the US population.

Methods: Using data from the Nurses' Health Study (1980-2014; n=78 865) and the Health Professionals Follow-up Study (1986-2014, n=44 354), we defined 5 low-risk lifestyle factors as never smoking, body mass index of 18.5 to 24.9 kg/m², ≥30 min/d of moderate to vigorous physical activity, moderate alcohol intake, and a high diet quality score (upper 40%), and estimated hazard ratios for the association of total lifestyle score (0-5 scale) with mortality. We used data from the NHANES (National Health and Nutrition Examination Surveys; 2013-2014) to estimate the distribution of the lifestyle score and the US Centers for Disease Control and Prevention WONDER database to derive the age-specific death rates of Americans. We applied the life table method to estimate life expectancy by levels of the lifestyle score.

Results: During up to 34 years of follow-up, we documented 42 167 deaths. The multivariable-adjusted hazard ratios for mortality in adults with 5 compared with zero low-risk factors were 0.26 (95% confidence interval [CI], 0.22-0.31) for all-cause mortality, 0.35 (95% CI, 0.27-0.45) for cancer mortality, and 0.18 (95% CI, 0.12-0.26) for cardiovascular disease mortality. The population-attributable risk of nonadherence to 5 low-risk factors was 60.7% (95% CI, 53.6-66.7) for all-cause mortality, 51.7% (95% CI, 37.1-62.9) for cancer mortality, and 71.7% (95% CI, 58.1-81.0) for cardiovascular disease mortality. We estimated that the life expectancy at age 50 years was 29.0 years (95% CI, 28.3-29.8) for women and 25.5 years (95% CI, 24.7-26.2) for men who adopted zero low-risk lifestyle factors. In contrast, for those who adopted all 5 low-risk factors, we projected a life expectancy at age 50 years of 43.1 years (95% CI, 41.3-44.9) for women and 37.6 years (95% CI, 35.8-39.4) for men. The projected life expectancy at age 50 years was on average 14.0 years (95% CI, 11.8-16.2) longer among female Americans with 5 low-risk factors compared with those with zero low-risk factors; for men, the difference was 12.2 years (95% CI, 10.1-14.2).

Conclusions: Adopting a healthy lifestyle could substantially reduce premature mortality and prolong life expectancy in US adults.

Keywords: healthy lifestyle; life expectancy; mortality, premature.

Figure 1. Life expectancy estimated based on overall mortality rate of Americans (CDC report), the prevalence of lifestyle factors using NHANES data 2013–2014 and age- and sex-specific hazard ratios (A: hazard ratio; B: life expectancy at age 50; C: life expectancy by age)^{*, †}

^*Low-risk lifestyle factors included: cigarette smoking (never smoking), physically active (≥3.5 hours/week moderate to vigorous intensity activity), high diet quality (upper 40% of alternative healthy eating index (AHEI), moderate alcohol intake of 5–15 g/day (female) or 5–30 g/day (male), and normal weight (body mass index <25 kg/m²). ^†The estimates of cumulative survival from 50 years of age onward among the 5 lifestyle risk factor groups were calculated by applying: (1) all-cause and cause-specific mortality rates were obtained from the US CDC WONDER database; (2) distribution of different numbers of low-risk lifestyles was based on the US NHANES 2013–2014; (3) multivariate-adjusted hazard ratios (sex-and age-specific) for all-cause mortality associated with the 5 low-risk lifestyles as compared to those without any low-risk lifestyle factors, adjusted for ethnicity, current multivitamin use, current aspirin use, family history of diabetes mellitus, myocardial infarction, or cancer, and menopausal status and hormone use (females only), were based on data from the NHS and HPFS.

Figure 2. Projected gained or lost life expectancy according to individual low-risk lifestyle factors (A: physical activity; B: smoking; C: diet; D: alcohol; E: body mass index)^*

^*The estimates of cumulative survival from 50 years of age onward among different levels of each lifestyle factor were calculated by applying: (1) all cause and cause-specific mortality rate were obtained from the US CDC WONDER database; (2) distributions of different groups of each lifestyle factor were based on the US NHANES 2013–2014; (3) multivariate-adjusted hazard ratios (gender-specific) for all-cause and cause-specific mortality associated with each lifestyle factor adjusted for ethnicity, current multivitamin use, current aspirin use, family history of diabetes mellitus, myocardial infarction, or cancer, menopausal status and hormone use (females only), were based on data from the NHS and HPFS.