Association of age at first birth and risk of non-alcoholic fatty liver disease in women: evidence from the NHANES.

Background: Numerous studies have suggested that age at first birth (AFB) is inversely associated with metabolic diseases, but positively associated with liver cancer in women. Non-alcoholic fatty liver disease (NAFLD) is a canonical example of metabolic dysfunction and inflammation-based liver disease, while the association between AFB and the risk of NAFLD remains unclear. We aimed to investigate the association between AFB and the odds of NAFLD in women.

Methods: Women older than 20 years at the time of the survey were analyzed using National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2018 in the US. AFB was obtained with self-administered questionnaires. NAFLD was diagnosed as fatty liver index (FLI) ≥ 60. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using logistic regression models.

Results: Of the 12,188 women included in this study, 5670 (46.5%) had NAFLD. Compared to individuals with AFB of 30-32 years old (reference group), the fully adjusted ORs and 95% CI in women with AFB < 18, 18-20, 21-23, and 24-26 years were 1.52 (95% CI 1.14, 2.03), 1.60 (95% CI 1.21, 2.11), 1.40 (95% CI 1.06, 1.84), and 1.33 (95% CI 1.01-1.76), respectively. Yet there was no significant difference between AFB of 27-29, 33-35, or > 35 years compared to the reference group.

Conclusions: Women with younger AFB have higher odds of NAFLD in later life. Policymakers should consider focusing on those with earlier AFB for screening and prevention of NAFLD.