Design and baseline characteristics of a prospective cohort study for determinants of osteoporotic fracture in community-dwelling elderly Japanese men: the Fujiwara-kyo osteoporosis risk in men (FORMEN) study

Abstract

Background: Osteoporosis and osteoporotic fracture in men are significant public health problems in an aging society. However, information on male osteoporosis remains impressively lacking, especially for Asians. We designed the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN) study as an ancillary study of a cohort study, the Fujiwara-kyo study, to determine risk factors for osteoporotic fractures in Japanese men.

Design: A community-based single-centre prospective cohort study with at least a 5-year follow-up.

Subjects: All the male participants of the Fujiwara-kyo study who were living in the four cities studied, aged 65 years and older, and able to walk without aid from others.

Primary outcome: Incidence of osteoporotic fractures including vertebral and clinical non-vertebral fractures. ADDITIONAL OUTCOMES: Change in bone mineral density (BMD), change in hip geometry, onset of receiving benefits from Long-term Care Insurance (LCI), health-related quality of life, and mortality. BASELINE MEASUREMENTS: BMD at the lumbar spine (LS) and hip (TH), hip geometry, vertebral deformity assessment, bone turnover markers, physical and cognitive performance, various medical and lifestyle factors, and geriatric psychosocial measures confirmed by interviews based on self-administrated questionnaires.OUTCOME SURVEILLANCE: Annual mail surveys and a follow-up survey at the fifth year comprising similar items to the baseline study will be used to determine the outcomes. Receipt of benefits from LCI and mortality will be obtained from the city governments.

Current status: The baseline study was conducted for 2174 eligible men, and 2012 completed the study and were eligible for follow-up. Prevalence rates of osteoporosis (BMD 2.5 SD or more below the young adult mean (YAM)) and low BMD (BMD 1 SD or more below YAM) in at least one of LS and TH were calculated to be 4.4% and 41.8%, respectively. The proportion of men with low BMD only at TH showed a significant increasing trend with aging (p < 0.0001) while that only at LS showed a decreasing trend (p = 0.0386). The prevalence rate of osteoporosis was underestimated when diagnosed using only BMD at LS. Other baseline measurements were successfully obtained.

Discussion: FORMEN baseline study was performed as designed and the FORMEN cohort study was successfully launched.

Figure 1

Study area of the Fujiwara-kyo study.

Figure 2

Time line of the Fujiwara-kyo study.

Figure 3

Proportions of BMD categories in age-stratified participants of the FORMEN baseline study, 2007-2008. BMD: Bone mineral density. Normal: BMD greater than 1 SD below the young adult mean (YAM). Low BMD: BMD 1 SD or more below YAM. LS: Lumbar spine. TH: Total hip. Data of 1912 subjects with BMD values available for both skeletal sites were used in the analysis.