Associations of Socioeconomic Status and Phenotypic Frailty With Incident COPD: Findings From UK Biobank Participants

Abstract

Background: The independent, mediation, interaction, and joint effects of socioeconomic status (SES) and phenotypic frailty on the incidence of COPD are unclear.

Research question: Do SES and frailty increase the risk of COPD independently or jointly? Is there an interaction between the 2 factors in incident COPD? Does frailty play a mediating role between SES and COPD?

Study design and methods: This study included 396,106 UK Biobank participants without COPD at baseline. Latent class analysis was used to define the SES of participants. Frailty was defined by the frailty phenotypes according to 5 factors. Cox regression models were used to examine the associations and calculate hazard ratios (HRs) and 95% CIs. Mediation and interaction analyses were used to explain the associations between SES and frailty on COPD risk.

Results: During a median follow-up period of 13.5 years, 12,626 individuals were diagnosed with COPD. Compared with high SES or robust individuals, low SES (HR, 2.69; 95% CI, 2.48-2.92) or frailty (HR, 2.75; 95% CI, 2.58-2.93) increased the risk of COPD, respectively; 11.80% of the association between SES and COPD was mediated by frailty. In addition, there was a statistically significant additive interaction of low SES and frailty with COPD incidence (relative risk due to interaction, 3.591; 95% CI, 2.189-4.992; attributable proportion due to the interaction, 0.433; 95% CI, 0.276-0.589). Compared with robust individuals with high SES, frail individuals with low SES have the highest risk of COPD (HR, 7.85; 95% CI, 6.96-8.86).

Interpretation: Our findings indicate that low SES and frailty are independent risk factors for COPD, and these 2 factors also have synergistic interaction in COPD. Frailty partially mediated the association between SES and COPD. Thus, the early identification and reversal of frailty may minimize the risk of COPD, especially in individuals with low SES.

Keywords: COPD; frailty; interaction; mediation; socioeconomic status.