African American race is associated with worse sleep quality in heavy smokers

STUDY OBJECTIVES: To examine the association of self-identified race with sleep quality in heavy smokers.

METHODS: We studied baseline data from 1965 Non-Hispanic White (NHW) and 462 African American (AA) participants from SPIROMICS with ≥20 pack-years smoking history. We first examined the PSQI's internal consistency and item-total correlation in a population with COPD. We then used staged multivariable regression to investigate the association of race and sleep quality as measured by the Pittsburgh Sleep Quality Index (PSQI). The first model included demographics; the second added measures of health status; the third, indicators of socio-economic status. We next explored the correlation between sleep quality with six-minute walk distance and St George's Respiratory Questionnaire score as COPD-relevant outcomes. We tested for interactions between self-identified race and the most important determinants of sleep quality in our conceptual model.

RESULTS: We found that the PSQI had good internal consistency, and item-total correlation in our study population of heavy smokers with-and-without COPD. AA race was associated with increased PSQI in univariable analysis and after adjustment for demographics, health status, and socio-environmental exposures (P=.02, 0.44 95%CI: 0.06 to 0.83). Increased PSQI was associated with lower post-bronchodilator FEV and lower household income, higher depressive symptoms, and female gender. We identified an interaction wherein depressive symptoms had a greater impact on PSQI score for Non-Hispanic White than African American participants (P-for-interaction=.01).

CONCLUSIONS: In heavy smokers, self-reported AA race is independently associated with worse sleep quality.

CLINICAL TRIAL REGISTRATION: Registry: ClinicalTrials.gov; Name: Study of COPD Subgroups and Biomarkers (SPIROMICS); Identifier: NCT01969344; URL: https://clinicaltrials.gov/ct2/show/NCT01969344.