YPrevalence and Risk Factors of NAFLD, High-Risk NASH, and Fibrosis Among Lean US Adults

Introduction: Non-alcoholic fatty liver disease (NAFLD) is a growing public health concern worldwide. Early detection and management of modifiable risk factors are critical to mitigating its impact. This study aimed to investigate the prevalence and risk factors of NAFLD, high risk non-alcoholic steatohepatitis (NASH), and fibrosis among lean adults in the United States. Methods: We used the latest National Health and Nutrition Examination Survey (NHANES) dataset from 2017-2020. Participants who were adults (≥18 years), have completed a transient elastography (TE) exam, and had BMI data were eligible for inclusion. We excluded individuals with BMI < 18.5 and >25kg/m2 (or >23 kg/m2 for Asians), those with heavy alcohol use ( >2 drinks/day for men, >1 for women), positive hepatitis C RNA or B surface antigen, and exposure to steatogenic drugs. Using controlled attenuation parameter (CAP) scores of ≥285 dB/m, we assessed the age-adjusted prevalence of lean NAFLD. To determine the age-adjusted prevalence of high-risk NASH and significant fibrosis, we used the FibroScan-AST (FAST) score (cut-offs 0.35) and vibration-controlled transient elastography (LSM ≥8kPa), respectively. Multivariate logistic regression was used to identify potential risk factors. Results: From the 15,560 NHANES participants (2017-2020), 1,628 adults, classified as lean, were eligible for our analysis (Table 1). The age-adjusted prevalence of NAFLD among lean adults was found to be 6.30% (95% confidence interval [CI]: 3.84-10.16%), with higher prevalence in adults aged 40 and above, and in certain ethnic groups (Figure 1). The prevalence of high-risk NASH (FAST > 0.35), was 1.29% (95% CI: 0.70-2.34%) among lean adults, higher in males, individuals over 60, and those with diabetes or hypertension. Significant fibrosis (LSM ≥8kPa) was prevalent in 4.35% (95% CI: 2.73-6.89%) of lean adults, and more common among older adults, NH Whites, and males. Older age, hypertension, diabetes, and dyslipidemia were associated with lean NAFLD. Hypertension was the only predictor of high-risk NASH (cut-off of 0.35) among lean adults. Additionally, lean adults with significant fibrosis (LSM ≥8.0 kPa) were more likely to be aged 60 years and over, and less likely to be of Asian descent. Conclusion: These findings suggest that the prevalence of NAFLD is of concern among lean individuals, particularly those aged 40 and older with metabolic comorbidities, while a targeted approach to screening and risk stratification for hepatic fibrosis upon lean NAFLD diagnosis is warranted.Figure 1.: Prevalence and risk factors of NAFLD, high-risk NASH and Fibrosis Among Lean US Adults. Table 1. - Study Participants Characteristics Total CAP < 285 dB/m CAP > 285 dB/m N=1,628 N=1,517 N=111 Age categories 18-39 764 (46.9%) 746 (49.2%) 18 (16.2%) 40-59 374 (23.0%) 340 (22.4%) 3 (30.6%) 60+ 490 (30.1%) 431 (28.4%) 59 (53.2%) Gender Female 847 (52.0%) 795 (52.4%) 52 (46.8%) Male 781 (48.0%) 722 (47.6%) 59 (53.2%) Race/ethnicity Non-Hispanic White 615 (37.8%) 566 (37.3%) 49 (44.1%) Hispanic 296 (18.2%) 274 (18.1%) 22 (19.8%) Non-Hispanic Black 386 (23.7%) 373 (24.6%) 13 (11.7%) Non-Hispanic Asian 240 (14.7%) 220 (14.5%) 20 (18.0%) Other 91 (5.6%) 84 (5.5%) 7 (6.3%) Diabetes status No diabetes 1,046 (64.3%) 1,004 (66.2%) 42 (37.8%) Prediabetes 138 (8.5%) 108 (7.1%) 30 (27.0%) Diabetes 444 (27.3%) 405 (26.7%) 39 (35.1%) Blood pressure No hypertension 1,075 (71.0%) 1,028 (73.0%) 47 (44.8%) Hypertension 439 (29.0%) 381 (27.0%) 58 (55.2%) Dyslipidemia status Normal lipids 842 (54.7%) 809 (56.5%) 33 (31.1%) Dyslipidemia 696 (45.3%) 623 (43.5%) 73 (68.9%) Metabolic syndrome status No metabolic syndrome 623 (85.7%) 590 (87.9%) 33 (58.9%) Metabolic syndrome 104 (14.3%) 81 (12.1%) 23 (41.1%) Abbreviations: controlled attenuation parameter (CAP).