Peak expiratory flow, walking speed and survival in older adults: An 18-year longitudinal population-based study

Background: Peak expiratory flow (PEF) and walking speed (WS) have been proposed as indicators of robustness and are independent predictors of health-related outcomes. We aimed to investigate how the co-occurrence of respiratory and physical impairments changes as a function of age, and to quantify the association of the combination of low PEF and slow WS on survival in older people. Methods: This prospective study analyzes data from 2656 community-dwelling participants (age ≥ 60 years) from the SNAC-K study. At baseline, we assessed: (1) sociodemographic, lifestyle and medical data; (2) respiratory function, estimated through PEF and expressed as standardized residual (SR) percentile; and (3) WS at usual pace, categorized as no (>1.2 m/s), mild (0.8–1.2 m/s) and moderate-to-severe (<0.8 m/s) walking impairment. Participants' vital status over an 18-year follow-up was derived from registers. The association of different combinations of PEF and WS on median survival time was estimated through Laplace regression adjusted for potential confounders. Results: Respiratory and walking impairments co-occurred more frequently with increasing age. Among individuals with PEF SR-percentiles < 10th, the percentage of moderate-to-severe walking impairment was 12.1% in sexagenarians, 35.7% in septuagenarians, and 75–80% in the oldest old. The greatest reduction in median survival time (−5.4 [95%CI: −6.4; −4.4] years, p < 0.001) was observed among people with combined respiratory and moderate-to-severe walking impairments, compared with those with no dysfunctions, who had a median survival time of 17.4 (95%CI: 17.0; 17.8) years. Conclusions: Impaired PEF and WS co-occur more frequently with advancing age, and their co-occurrence is associated with shorter survival.