Effects of additive interactions among obesity, visceral adiposity, and sarcopenia on nonalcoholic fatty liver disease

Although the association of nonalcoholic fatty liver disease (NAFLD) with obesity or sarcopenia is known, few studies have investigated the combined effect of various body composition parameters on the risk of NAFLD. Thus, the aim of this study was to evaluate effects of interactions between various body composition parameters, including obesity, visceral adiposity, and sarcopenia, on NAFLD. Data of subjects who underwent health checkups between 2010 and December 2020 were retrospectively analyzed. Body composition parameters including appendicular skeletal muscle mass (ASM) and visceral adiposity were assessed using bioelectrical impedance analysis. Sarcopenia was defined as ASM/weight beyond two standard deviations below the gender-specific mean for healthy young adults. NAFLD was diagnosed using hepatic ultrasonography. Interaction analyses, including relative excess risk due to interaction (RERI), synergy index (SI), and attributable proportion due to interaction (AP), were performed. Among a total of 17,540 subjects (mean age: 46.7 years, 49.4% males), the prevalence of NAFLD was 35.9%. The odds ratio (OR) of interaction between obesity and visceral adiposity affecting NAFLD was 9.14 (95% CI: 8.29–10.07). The RERI was 2.63 (95% CI: 1.71–3.55), SI was 1.48 (95% CI: 1.29–1.69) and AP was 29%. The OR of interaction between obesity and sarcopenia affecting NAFLD was 8.46 (95% CI: 7.01–10.21). The RERI was 2.21 (95% CI: 0.51–3.90). SI was 1.42(95% CI: 1.11–1.82) and AP was 26%. The OR of interaction between sarcopenia and visceral adiposity affecting NAFLD was 7.25 (95% CI: 6.04–8.71), however, there was no significant additive interaction with RERI = 0.87 (95% CI: −0.76 to 2.51). Obesity, visceral adiposity, and sarcopenia were found to be positively associated with NAFLD. Obesity, visceral adiposity, and sarcopenia were found to have additive interaction effects on NAFLD.