Elevated serum liver enzymes and fatty liver changes associated with long driving among taxi drivers

Abstract

Previous studies suggested increased morbidities and mortalities of liver diseases in drivers. To examine whether driving (monthly driving distance; tenure) is associated with elevated alanine aminotransferase (ALT), aspartate aminotransferase (AST), or chronic fatty liver (FL) changes, we performed a cross-sectional, secondary analysis of the Taxi Drivers' Health Study (n = 1,355), adjusting for clinical, demographic, and lifestyle factors. Prevalence of elevated ALT, elevated AST, and fatty liver changes were 22.0%, 5.1%, and 9.3%, respectively. Driving distance had a positive association with elevated ALT with a prevalence ratio of 1.35 (95% CI: 0.98, 1.89) comparing the highest versus lowest driving quartile. This association differed by alcohol use, with a corresponding prevalence ratio of 2.08 (95% CI: 1.30, 3.33) among "past/current" drinkers but no association among "never" drinkers. Similar patterns were found for AST, but estimates were less stable. We found a curvilinear response pattern for fatty liver changes; prevalence first increased with years as a taxi driver and then receded in the highest ranges of driving tenure, regardless of the alcohol history. Our results provide evidence that long driving is associated with both short-term and chronic liver insults, although alcohol use appears to modify this putative effect.