Peak expiratory flow as a predictor of subsequent disability and death in community-living older persons

Abstract

Objectives: To determine whether peak expiratory flow (PEF), when expressed by a validated method using standardized residual (SR) percentile, is associated with subsequent disability and death in older persons.

Design: Prospective cohort study.

Setting: New Haven, Connecticut.

Participants: Seven hundred fifty-four initially nondisabled, community-living persons aged 70 and older.

Measurements: PEF was assessed at baseline along with chronic conditions and smoking history. The onset of persistent disability in activities of daily living (ADLs), continuous mobility disability, and death were ascertained during monthly interviews over a 5-year period.

Results: Participants' mean age was 78.4, 63.7% had a smoking history, and 17.4% reported chronic lung disease. The incidence rates per 100 person-months were 1.00 (95% confidence interval (CI)=0.90-1.12) for ADL disability, 0.80 (95% CI=0.70-0.93) for mobility disability, and 0.44 (95% CI=0.38-0.51) for death. At a PEF less than 10(th) SR percentile, identifying nearly one-quarter of the cohort, hazard ratios (HRs) adjusted for multiple confounders, including age, smoking, and chronic lung disease, demonstrated a greater risk of ADL disability (HR=1.79, 95% CI=1.23-2.62), mobility disability (HR=1.89, 95% CI=1.15-3.10), and death (HR=2.31, 95% CI=1.29-4.12).

Conclusion: In an elderly cohort, it was found that low PEF, when expressed as an SR percentile, is independently associated with subsequent disability and death. These results support the use of PEF as a potentially valuable risk assessment tool in community-living older persons.

Conflict of interest statement

The authors report no conflicts of interest.

Figures

Figure 1. Kaplan-Meier curves stratified by peak flow (PEF) stage

For the analysis of disability in activities of daily living (ADL) and death, the number of participants at risk in stages 1 through 5 was 120, 160, 127, 172, and 174, respectively, for a total of 753. For the analysis of mobility disability, the number of participants at risk in stages 1 through 5 was 102, 129, 95, 122, and 112, respectively, for a total of 560. Statistical significance was determined by the log rank test.