Self-reported number of remaining teeth is associated with bone mineral density of the femoral neck, but not of the spine, in Japanese men and women

Recent studies suggest that a small number of remaining teeth may be associated with low skeletal bone mineral density (BMD) in postmenopausal women. Estrogen deficiency after menopause is considered potential cause relating to tooth loss accompanied by low skeletal BMD in women. Since estrogen plays a dominant role in regulating the male skeleton, it is likely that a small number of remaining teeth also may be associated with low skeletal BMD in men. However, it remains uncertain whether tooth loss is associated with low skeletal BMD in both men and women. We investigated the association between self-reported number of remaining teeth and BMD of the spine and the femoral neck in a cohort of 1914 Japanese subjects aged 48-95 years who were recruited from the Adult Health Study conducted by the Radiation Effects Research Foundation (RERF). BMD of the spine and the femoral neck was measured by dual energy X-ray absorptiometry (DXA). Tooth count was self-reported in response to a simple question to subjects about the number of remaining teeth they had at the time of the survey. Multiple regression analysis adjusted for age, weight, height, smoking, estrogen use, and years since menopause revealed a significant association between number of remaining teeth and BMD of the femoral neck in both men and women; however, no association was found between number of remaining teeth and BMD of the spine in both sexes. Retention of four teeth was significantly associated with a 0.004 g/cm(2) increase in femoral neck BMD in men (P<0.05), which was similar to that observed in women (P<0.01). Our results suggest the presence of common causes, except age and body weight, relating to tooth loss accompanied by low BMD of the femoral neck in both men and women.