Vaping and smoking as risk factors for arthritis: Evidence from double machine learning.

Smoking is a well-documented risk factor for chronic diseases, including arthritis. Vaping, often marketed as a safer alternative, has risen sharply, yet its implications for musculoskeletal health remain unclear. We examine the associations of vaping and smoking with arthritis using Double Machine Learning (DML), and present illustrative economic scenarios projecting the potential cost implications of arthritis cases associated with these behaviors. Data from the Behavioral Risk Factor Surveillance System (BRFSS) of the Centers for Disease Control and Prevention (CDC), collected in the United States, for adults aged 18-64 years (N = 36,768) is used. Arthritis is the outcome variable; vaping and smoking are the exposure variables, with estimates conditioned on twenty-seven demographic, behavioral, and health-related covariates (See Table 1). Results show that vaping is associated with a 2.12 percentage point higher prevalence of arthritis than among non-vapers, while smoking is associated with a 2.22 percentage points increase compared with non-smokers. When accounting for concurrent nicotine behaviors, the estimated associations remain largely stable, with smoking exhibiting a slightly larger estimate of 2.14 percentage points while vaping attenuated to 1.91 percentage points. Vaping was estimated to be associated with approximately 190,581-254,109 arthritis cases annually, corresponding to a potential economic cost projection of $133.4--$177.9 million. Smoking was statistically associated with approximately 518,886-687,413 cases, corresponding to $363.2 -$481.2 million. Combined, the projected economic burden associated with vaping and smoking was approximately $496.6-$659.1 million annually under conservative assumptions. Relative to published estimates of the total U.S. arthritis burden, these projections represent approximately 0.09%-0.22% of arthritis-related expenditures under direct healthcare cost assumptions and up to 9.23% when broader indirect and societal costs are considered. Our findings suggest that vaping is associated with musculoskeletal risk comparable to, or potentially exceeding, that of smoking, and do not support the perception of vaping as a risk-free alternative. The illustrative projections may inform policy discussions on vaping and smoking in relation to the broader arthritis-related health and economic burden.