Evaluation of Racial Differences and Association of Obesity on Elevated ALT Level: 10-Year Analysis of the National Health and Nutrition Examination Survey (NHANES)

Abstract

Introduction: Obesity is a risk factor for non-alcoholic fatty liver disease (NAFLD) and it has important public health impact. Racial differences in alanine aminotransferase (ALT) levels have not been well described. This study aimed to identify racial differences on abnormal ALT levels in patients without liver disease and evaluate the association between obesity and elevated ALT levels in adults without other metabolic risk factors. Methods: The National Health and Nutrition Examination Survey was used to compare ALT levels by race and gender. Logistic regression models were constructed to evaluate the impact of obesity on elevated ALT and to identify potential risk factors for abnormal ALT levels. Obesity was classified according to BMI with WHO classification. Serum ALT levels were considered abnormal if >47 mg/dL in males and >35 mg/dL in females. We constructed multivariable logistic regression models using STATA software version 13. Results: We analyzed 9,025 patients. 2,347 patients (26%) were obese or morbidly obese, 2,099 patients (23%) were overweight, 2,772 had normal weight (31%) and 1,807 patients had BMI below the normal range (20%). No significant difference in ALT levels across overall races was found, however on the Hispanic subgroup analysis we found significant differences between Mexican when compared to Other Hispanics (Latinos from Central America and South America); (aOR 1.76, p < 0.01; CI: 1.3-2.1). Whites were not associated with high ALT levels and African Americans were the most unlikely to have high ALT levels (aOR 0.30, p < 0.01; CI: 0.20-0.44). Obesity was not significantly associated with elevated ALT (aOR 1.05, p < 0.7; CI: 0.7-1.5). However, Waist circumference was (aOR 1.04, p < 0.01; CI: 1.02-1.4). Female gender was protective against high ALT level (aOR 0.31, p < 0.01; CI: 0.24-0.40). Conclusion: Limitations: Retrospective study. Strength: Nationwide patient cohort. Incomplete comorbidity adjustment. Conclusion: Racial differences in ALT levels among adults are plausible. Mexican ethnicity but not Hispanic overall were significantly associated with higher levels of ALT. Abdominal obesity but not Overall obesity, in the absence of metabolic risk factors and other causes of liver disease, is associated with elevated ALT, providing evidence that abdominal lipotoxicity has may do more harm. These findings have important epidemiologic implications and need more investigations as it is a possible target for new screening interventions.