The correlation between serum levels of alkaline phosphatase and bone mineral density in adults aged 20 to 59 years

Serum alkaline phosphatase (ALP) plays an important role in bone metabolism. However, the association between serum ALP and bone mineral density (BMD) remains inconclusive. Therefore, this study aimed to explore the relationship between serum ALP levels and pelvic BMD in young adults. We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey conducted from 2011 to 2016. Serum ALP levels and pelvic BMD were analyzed as independent and dependent variables, respectively. Weighted multivariate linear regression models and stratified analysis by age, sex, and race/ethnicity were applied after controlling for confounding factors to assess the relationship between serum ALP and pelvic BMD. Smooth curve fitting and threshold effect analysis were used to describe the nonlinear relationship between the 2 variables. A total of 7796 participants (4063 males and 3733 females) aged 20 to 59 years were included in this study. When serum ALP was represented as a continuous variable and fully adjusted in the regression model, ALP was significantly negatively correlated with pelvic BMD (β = −0.0008, 95% confidence interval: −0.0010 to −0.0006, P < .000001); this significant negative correlation persisted when ALP was transformed into a categorical variable, and was consistent in subgroup analyses. Additionally, smooth curve fitting and threshold effect analysis showed a persistent negative correlation between serum ALP and pelvic BMD, with a saturation effect at 97 U/L. Our results revealed a negative correlation between serum ALP levels and pelvic BMD in young adults. Monitoring serum ALP levels could help in the early detection of risks for bone metabolic disorders such as osteoporosis.