PURPOSE: To identify significant covariates predicting mortality in elderly subjects with obstructive airway disease (OAD).
METHODS: 268 subjects with OAD were identified based on American Thoracic Society criteria from the ‘Health, Aging and Body Composition (HABC)’ study, a community-based observational cohort of 3075 well-functioning Black and White men and women aged 70-79. During an average follow-up of 5.5 years, 83 subjects with OAD died. Baseline covariates such as percent predicted forced expiratory volume in 1 second (PPFEV1), body mass index, self-reported dyspnea, long distance corridor walk, knee extensor strength (dynamometer), smoking status, pack-years of smoking, race, gender and serum concentrations of three inflammatory markers (interleukin-6 [IL-6], C-reactive protein [CRP], and tumor necrosis factor-α; [TNF-α]) were evaluated for their association with all cause mortality. Covariates were coded such that a higher score signified a greater deviation from normal values. Variables that univariately associated with mortality were evaluated for their independent association by Cox proportional regression modeling. Based on the final model, a multidimensional 10-point index was constructed and hazard ratios (HR) were calculated.
RESULTS: Lower PPFEV1 (HR=2.03, P<0.0001), lower knee strength (HR 1.26, P=0.001), elevated IL-6 and CRP levels (HR 1.37, P=0.0002, HR 1.18, P=0.04, respectively), significantly predicted mortality. The final index (PILE), ranging from 1 to 10, incorporated PPFEV1 (P), IL-6 (IL) and knee extensor strength (E). Each 1 point increase in PILE score was associated with a 22% increase (95% CI 11.8–34.7%) in mortality after adjusting for race, gender, age, smoking status and comorbid conditions. Subjects with a PILE score of 10 (n=16; 56% dead) had a 5.8-fold higher risk of death compared to individuals with a PILE score of 1 (n=17; 0% dead).
CONCLUSION: The PILE index capturing pulmonary function, knee extensor strength, and systemic inflammatory response (IL-6) predicts mortality in a cohort of elderly subjects with OAD. Validation in an independent sample is warranted before generalization of these results.
CLINICAL IMPLICATIONS: Risk of mortality for subjects with OAD can potentially be incorporated in clinical decision making.
DISCLOSURE: Nitin Mehrotra, None.