Serum alkaline phosphatase, a risk factor for non-alcoholic fatty liver, but only for women in their 30s and 40s: evidence from a large cohort study

Background: Several risk factors are able to predict non-alcoholic fatty liver (NAFL) development, but the predictive value of serum alkaline phosphatase (ALP) remains uncertain. Our aim is to investigate the association between serum ALP levels and NAFL. Methods: 21,331 NAFL-free subjects were included. Sex-specific ALP quartiles (Q1 to Q4) were defined. With Q1 used as reference, hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated across each quartile. Results: After adjusting for confounding variables, values in Q2, Q3 and Q4 had HRs (95%CIs) of 1.16 (0.94–1.43), 1.38 (1.13–1.69), 1.51 (1.24–1.83) in females and 0.99 (0.90–1.09), 1.04 (0.95–1.14), 0.96 (0.87–1.05) in males, respectively. A subgroup analysis of age factors in females, from Q2 to Q4, adjusted HRs (95%CIs) were 1.31 (0.81–1.99), 1.86 (1.23–2.81), 2.44 (1.60–3.71) in their 30 s, 1.13 (0.83–1.54), 1.17 (0.85–1.62), 1.65 (1.22–2.25) in their 40 s, and 0.95 (0.51–1.78), 0.91 (0.52–1.62), 0.89 (0.53–1.52) in their 50 s. Conclusions: Higher serum ALP levels are considered a significant predictor for NAFL development in females aged 30 to 50.