Determinants of bone health in elderly Japanese men: study design and key findings of the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) cohort study oleh Yuki Fujita, Junko Tamaki, Katsuyasu Kouda, Akiko Yura, Yuho Sato, Takahiro Tachiki, Masami Hamada, Etsuko Kajita, Kuniyasu Kamiya, Kazuki Kaji, Koji Tsuda, Kumiko Ohara, Jong-Seong Moon, Jun Kitagawa, Masayuki Iki, the FORMEN study group