Statistical analysis
Survey responses were tabulated and reported as counts and percentages.
Current users were compared to non-current users of each substance for
all analyses. To assess differences in socioeconomic characteristics,
demographics, and illness severity markers, Fishers exact test was used.
Univariate and multivariate logistic regressions were performed to
evaluate the unadjusted and adjusted association between usage of CFTR
modulators and current usage of each substance. Potential confounders
included in the multivariate models were chosen a priori based on
prior literature and a directed acyclic graph of the framework of
potential relationships of use of CFTR modulators and substance use.
Potential confounders were gender (female, male, other), age (13-25,
26-39, 40-80 years old), race and ethnicity (non-Hispanic White,
Asian/Black/Hispanic/other race), FEV1 percent predicted
(<60%, 60-79%, >80%), PHQ-4 (normal/mild,
moderate/severe). Subjects with missing data were excluded from the
regression analyses. A p-value of less than 0.05 was considered
statistically significant. All statistical analyses were conducted using
R version 4.2.1 (R Foundation for Statistical Computing, Vienna,
Austria). The study procedures were reviewed and approved by the
Institutional Review Board at the University of California, San
Francisco (21-34926).