Waist-to-height ratio and non-alcoholic fatty liver disease in adults.

BACKGROUND

The waist-to-height ratio (WHtR) has been recognised as a powerful indicator to evaluate non-alcoholic fatty liver disease (NAFLD) in recent years, but few related studies are available. Thus, clarifying the association between the WHtR and NAFLD may be beneficial to the prevention and treatment of NAFLD.

METHODS

The cross-sectional study population was from a large-scale health examination programme called 'human dock' in Japan. In this study, 14,125 participants in this health examination programme were included. To understand the association between the WHtR and NAFLD more intuitively, we grouped the WHtR values into quintiles and used a multivariable logistic regression model to assess WHtR and its quintile with NAFLD risk. Moreover, we used the generalised additive model to model the association between WHtR and NAFLD to explore their non-linear relationship.

RESULTS

The prevalence of NAFLD among participants in this study was 17.59%, with an average age of 43.53 ± 8.89 years. After adjusting for all non-collinear covariables, we observed a 66% increase in the NAFLD risk per SD increase in WHtR. Furthermore, in the quintile groups of WHtR, the participants in quintile 2, quintile 3, quintile 4, and quintile 5 had 3.62-fold, 5.98-fold, 9.55-fold, and 11.08-fold increased risks of NAFLD, respectively, compared with those in quintile 1 (P < 0.0001). Non-linear relationship analysis revealed threshold and saturation effects between WHtR and NAFLD in which a WHtR of approximately 0.4 might be the threshold effect of NAFLD risk, 0.6 might be the saturation effect of NAFLD risk. Additionally, subgroup analysis showed that the interaction between WHtR and BMI was significant.

CONCLUSIONS

Our results suggest that in adults, the WHtR is associated with NAFLD, and the association is not purely linear but non-linear, with significant threshold and saturation effects.