Abstract
Background: Item-Response Theory (IRT) is a modern psychometric technique able to develop a true score measure of Health-Related Quality Of Life (HRQOL) from survey data. The purpose of this study was to investigate both Physical Inactivity (PIA) and HRQOL as predictors of survival, with the aid of IRT.
Methods: Data for this research came from the 2001-02 NHANES and its corresponding linked mortality file. PIA status was determined from survey questions regarding moderate and vigorous leisure-time physical activity. HRQOL was assessed by entering five perceived health variables into a single parameter IRT model. Cox proportional hazards regression was used to model the effects of PIA and HRQOL on survival time while controlling for confounding variables (age, sex, race and income).
Results: A total of 5,985 adults were included in this analysis with a mean person-year follow-up of 9.24 years and 965 deaths. Adjusted model showed a significant (p = .006) three-way (HRQOL×PIA×SEX) interaction, requiring a stratified analysis. Among females, those with poor HRQOL had shorter survival time (Hazard Ratio (HR) = 3.08, 95% CI: 1.24, 7.65) than those with good HRQOL. Physically inactive females showed shorter survival time (HR = 1.88, 95% CI: 1.24, 2.85) as compared to those who were not physically inactive. Since the two-way (HRQOL×PIA) interaction was significant (p = .004), the analysis for males was further stratified by PIA status. Among males who were physically inactive, those with poor HRQOL showed shorter survival time (HR = 2.39, 95% CI: 1.46, 3.90) than their counterparts with good HRQOL. Among males with poor HRQOL, those who were physically inactive showed shorter survival time (HR = 4.25, 95% CI: 2.30, 7.83) than their counterparts who were not physically inactive.
Conclusion: Results from this study support both HRQOL and PIA as predictors of survival time. Health promotion programs should include physical activity in adults with poor HRQOL.
Citation
Hart PD. Physical Inactivity and Health-Related Quality of Life as Predictors of Survival in US Adults: A Novel Use of Item-Response Theory. SM Prev Med Public Health. 2017; 1(2): 1010.