Osteoporosis genetic risk prediction using bone mineral density polygenic scores in Japanese: TMM CommCohort study.

Osteoporosis and fractures are major health concerns. We developed and validated a polygenic score (PGS) for quantitative ultrasound (QUS)-defined osteoporosis risk in Japanese individuals using heel QUS-derived T-scores. Genome-wide association study summary statistics from up to 10,794 participants in the Tohoku Medical Megabank Community-Based Cohort identified genome-wide significant loci, including MBL2, TMEM135, and WNT16. PGS models were constructed and evaluated using independent datasets for model selection (n = 1419) and validation (n = 8711). Adding the PGS to age and sex yielded only modest improvements in discrimination, whereas PGS quintiles supported genetic risk stratification. Compared with the intermediate group, individuals in the lowest PGS quintile had higher odds of the outcome (1.22, 95% confidence interval [CI]: 1.07-1.40), whereas those in the highest quintile had lower odds (0.85, 95% CI: 0.74-0.98). During prospective follow-up (mean 3.5 years), a similar gradient was observed, with higher incidence rate ratios in the lowest quintile (1.42, 95% CI: 1.17-1.73) and lower incidence rate ratios in the highest quintile (0.70, 95% CI: 0.54-0.89). No statistically significant interaction between age and PGS was observed, and age-T-score regression analyses showed no differences in age-related T-score decline across genetic risk groups. However, analyses in young adults (20-44 years) and extrapolation to age 20 suggested lower bone status around peak bone mass in individuals at high genetic risk for QUS-defined osteoporosis. These findings suggest that a Japanese-specific PGS may help identify individuals at elevated genetic risk earlier in adulthood.