We investigated risk factors for decreased calcaneus stiffness as an index of osteoporosis in Japanese elderly perpersons with a cohort study. Calcaneus stiffness was obtained through ultrasonographic heel measurement for 214 subjects (162 women and 52 men) who voluntarily participated in the baseline survey in 2000. Body mass index (BMI), medical history, oral health status, smoking cigarettes, alcoholic drinking, physical activities, and frequency of various foods intake were surveyed at that time. Stiffness was again measured among 93 subjects (70 women and 23 men) of them (43.5%) in the follow-up survey in 2005. Risk factors for decreased stiffness were evaluated using the unconditional logistic regression model adjusted for age and BMI by sex. Tooth loss was not associated with risk of decreased stiffness. From the results of stiffness in 2005 as a dependent variable, less frequent intake of vinegared dishes (OR=3.9, 95%CI: 1.3-11.6) and seaweed (OR=4.5, 95%CI: 1.5-14.2) in females as well as less frequent intake of green or yellow vegetables in males (OR=28.0, 95%CI: 2.5-317.4) were sigsignificantly associated with risk of decreased stiffness. From the results of change in stiffness as a dependent variable, less frequent intake of soybean products except for fermented soybeans (OR=3.2, 95%CI: 1.1-9.1) was significantly associated with risk of decreased stiffness in females. None of the other variables were significantly associated with risk of decreased stiffness. Dietary habits might play a role in calcium enrichment of the systemic bone. Further study is necessary to assess the relationship of dietary habits to risk of osteoporosis
