Association of Bone Metabolism with Fatty Liver Disease in the Elderly in Japan: A Community-based Study

Objective With the aging of society, both osteoporosis and fatty liver disease (FLD) are becoming important issues. However, the relationship between osteoporosis and FLD remains controversial. We investigated the association between bone metabolism and FLD in a Japanese community in a cross-sectional study. Methods A total of 1,020 participants were enrolled in a health survey. FLD was diagnosed by ultrasonography. Bone metabolism was evaluated based on bone mineral density (BMD), which was assessed using dual-energy X-ray absorptiometry, and with the bone formation index (total type I procollagen N-terminal propeptide/bone-alkaline phosphatase ratio; P1NP/BAP ratio) and the bone resorption index (crosslinked N-telopeptide of type I collagen/tartrate-resistant acid phosphatase-5b ratio; NTx/TRACP-5b ratio) calculated from serum bone turnover markers. Results The BMD (percentage of the young adult mean) was the same level in both male and female participants with and without FLD. Both men and women showed an age-dependent decrease in their bone formation index and bone resorption index values. Men of ≥70 years of age and women of 60-69 years of age with FLD had significantly lower bone formation index values and higher bone resorption index values. However, similar findings were not seen in women of ≥70 years of age. Conclusion Although the BMD levels were the same, regardless of the presence or absence of FLD, elderly participants with FLD showed decreased bone formation and increased bone resorption, with sex differences. Because our results suggest that FLD in elderly individuals is detrimental for bone metabolism, and that it leads to bone loss and osteoporosis, further studies using a cohort population are warranted.