Many studies examining the physical activity (PA) guidelines (PAG) use the least active participants as a reference for all group comparisons. Moreover, participants not meeting PAG may suffer from health conditions that confound the PA and outcome relationship. Purpose: The first aim of this study was to examine the extent to which initially healthy adults in different PAGgroups vary in their risk of heart disease (HD) mortality. The second aim was to determine if combined PAG groups differ when predicting HD mortality risk. Methods: A total of 405,994 participants from the 1997-2018 National Health Interview Survey (NHIS) were used and linked to the National Center for Health Statistics (NCHS) 2019 public-use mortality files. Only adults 18+ years of age, free from disease, eligible for linkage, with complete data were included. Four different PAG groups were created to include 1) those not meeting either aerobic PA or muscle strengthening (MS) guidelines (PAG1), 2) those meeting MS guidelines only (PAG2), 3) those meeting aerobic PAG only (PAG3), and 4) those meeting both aerobic PA and MS guidelines (PAG4). The analysis strategy included three goals: 1) examine the association between PAG groups and HD mortality risk using the conventional PAG1 as the reference category, 2) perform all PAG group comparisons in relation to HD mortality risk, and 3) test for differences in combined PAG groups using linear contrasts. The Kaplan-Meier (KM) method with log-rank (LR) test was used to compare survival curves between the PAG groups.Cox regression was used to address the above goals and estimate the hazard ratio (HR) and its 95% confidence interval (CI). Control variables included age, sex, race, income, BMI categories, and smoking status. Results: The median follow-up was 11.4 (SE=0.02) years with 7,849 (1.9%) HD-related deaths in the sample. Among HD survivors, 47.4% (SE=0.20), 3.5% (SE=0.04), 28.3% (SE=0.14), and 20.8% (SE=0.14) were categorized at baseline as PAG1, PAG2, PAG3, and PAG4, respectively. Whereas among those experiencing HD death, 69.4% (SE=0.68), 3.1% (SE=0.24), 20.3% (SE=0.54), and 7.3% (SE=0.40) were categorized at baseline as PAG1, PAG2, PAG3, and PAG4, respectively. Survival curves were significantly (KM LR p < .0001) different across the four PAG groups. The initial hazards model showed PAG2 (HR=0.75, 0.64-0.88), PAG3 (HR=0.65, 0.61-0.70), and PAG4 (HR=0.52, 0.46-0.59) with lower risk of HD mortality as compared to PAG1 (p for trend <0.0001). In multiple comparison analysis, PAG4 had lower risk of HD mortality as compared to PAG2 (HR=0.69, adj 0.54-0.90) and PAG3 (HR=0.80, adj 0.68-0.95). While PAG2 and PAG3 did not see significantly different (adj p=0.6811) HD mortality risk. Tests of linear contrasts showed that PAG4 had significantly lower (HR=0.29, adj 0.18-0.48) risk of HD mortality as compared to the other three groups combined. Additionally, PAG2, PAG3, and PAG4 combined had significantly lower (HR=0.25, adj 0.19-0.35) risk of HD mortality as compared to PAG1. Conclusion: These findings indicate that meeting any PAG may protect against HD mortality but meeting both could provide optimal benefit.

Physical activity, Heart disease, Mortality, Population health