Global incidence of non-alcoholic fatty liver disease: A systematic review and meta-analysis of 63 studies and 1,201,807 persons

Abstract

Background & aims: The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing. We aimed to estimate the pooled global NAFLD incidence.

Methods: We performed a systematic review and meta-analysis of cohort studies of adults without NAFLD at baseline to evaluate the global incidence of ultrasound-diagnosed NAFLD.

Results: A total of 63 eligible studies (1,201,807 persons) were analyzed. Studies were from Mainland China/Hong Kong (n = 26), South Korea (n = 22), Japan (n = 14), other (n = 2, Sri Lanka, Israel); 63.8% were clinical center studies; median study year 2000 to 2016; 87% were good quality. Among the 1,201,807 persons at risk, 242,568 persons developed NAFLD, with an incidence rate of 4,612.8 (95% CI 3,931.5-5,294.2) per 100,000 person-years and no statistically significant differences by study sample size (p = 0.90) or study setting (p = 0.055). Males had higher incidence vs. females (5,943.8 vs. 3,671.7, p = 0.0013). Both the obese (vs. non-obese) and the overweight/obese groups (vs. normal weight) were about threefold more likely to develop NAFLD (8,669.6 vs. 2,963.9 and 8,416.6 vs. 3,358.2, respectively) (both p <0.0001). Smokers had higher incidence than non-smokers (8,043.2 vs. 4,689.7, p = 0.046). By meta-regression, adjusting for study year, study setting, and study location, study period of 2010 or after and study setting were associated with increased incidence (p = 0.010 and p = 0.055, respectively). By country, China had a higher NAFLD incidence compared to non-China regions (p = 0.012) and Japan a lower incidence compared to non-Japan regions (p = 0.005).

Conclusions: NAFLD incidence is increasing with a current estimate of 4,613 new cases per 100,000 person-years. Males and overweight/obese individuals had significantly higher incidence rates compared to females and those of normal weight. Public health interventions for prevention of NAFLD are needed with a special emphasis on males, overweight/obese individuals, and higher risk regions.

Impact and implications: Non-alcoholic fatty liver disease (NAFLD) affects approximately 30% of people worldwide and appears to be increasing, but data to estimate the incidence rate are limited. In this meta-analytic study of over 1.2 million people, we estimated an incidence rate of NAFLD of 46.13 per 1,000 person-years with significant differences by sex, BMI, geography, and time-period. As treatment options for NAFLD remain limited, prevention of NAFLD should remain the focus of public health strategies. Studies such as these can help policy makers in determining which and whether their interventions are impactful.

Keywords: cohort studies; epidemiology; metabolic liver disease; risk factors.