Development And Testing Of An Integrated Score For Physical Behaviors

Abstract

There is expanding interest in the 24-hr activity cycle in relation to health outcomes, creating a need for new statistical approaches to analyze the joint effects of distinct but inter-related physical behaviors (e.g., exercise, sitting time, sleep). PURPOSE: To develop and test an integrated physical behavior score (PBS) in relation to all-cause and cause specific mortality. METHODS: NIH-AARP Diet and Health Study participants (N=163,016) completed a questionnaire (2004-2006) asking about time spent in five exercise and non-exercise physical activities, two sedentary behaviors (television and non-television), and sleep. In half of the sample, we used shape constrained additive regression to model the relationship between each behavior and survival. Maximum logit scores from each of the eight behavior-survival functions were summed to produce a PBS that was proportionally rescaled to range from 0-100. We examined predictive validity of the PBS in the other half-sample using Cox Proportional Hazards models after adjustment for covariates for all-cause and cause-specific mortality. RESULTS: In the testing sample, over an average of 6.6y of follow-up, 8,732 deaths occurred. We found a strong graded decline in risk of all-cause mortality across quintiles of PBS (Q5 vs Q1 hazard ratio [95%CI] = 0.53 [0.49, 0.57]). Risk estimates for the PBS were higher than any of the components in isolation. Results were similar but stronger for cardiovascular disease (Q5 vs Q1 = 0.42 [0.39, 0.48]) and other mortality (Q5 vs Q1 = 0.42 [0.36, 0.48]). The relationship between PBS and mortality was observed in stratified analyses by median age, sex, BMI and health status. CONCLUSIONS: Although widespread in other areas of epidemiology, this is one of the first attempts to characterize integrate multiple distinct physical behaviors into a single composite score. In a large sample of US adults, we showed this score has strong predictive validity for both men and women. Future research is needed to test this approach in an independent sample. Supported by the National Institutes of Health U01-CA057030 and the Intramural Research Program.