Cohort Profile: The Japanese Population-based Osteoporosis (JPOS) Cohort Study.

The Japanese Population-based Osteoporosis (JPOS) Cohort Study was launched in 1996 to produce a reference database of areal bone mineral density (aBMD) by dual energy X-ray absorptiometry (DXA) and bone turnover markers in the Japanese female population and to determine risk factors for osteoporotic fractures. At baseline, 3984 women aged 15 to 79 years were randomly selected to provide representative bone status data and aBMD values for the diagnosis of osteoporosis. Follow-up surveys were conducted in 1999, 2002, 2006 and 2011/12 to determine changes in aBMD and identify incident morphometry-confirmed vertebral fractures and clinical fractures. These outcomes were obtained from 2174 women who participated in at least one follow-up survey. JPOS is a unique resource of individual-level bone health information with radiological and biological archives that include DXA images, and serum, plasma and DNA for future analyses with emerging radiological and biological techniques. The JPOS dataset is not freely available, but new collaborations are encouraged. Potential collaborators are invited to contact the Secretary General (M.I.) at the administrative office of the JPOS Study Group.

Tracking of appendicular bone mineral density for 6 years including the pubertal growth spurt: Japanese Population-based Osteoporosis kids cohort study.

Bone development up to early adulthood plays an important role in determining the risk of osteoporosis later in life. However, bone development in children has not been fully documented by longitudinal studies in Japanese children. The purpose of this study is to determine the degree of tracking of areal bone mineral density (aBMD) from pre-puberty to 6-year follow-up, and to determine the target period to achieve maximal peak aBMD. This study was conducted as the pediatric part of a larger cohort study, the Japanese Population-based Osteoporosis (JPOS) study. Of 448 children aged 9-12 years who completed the baseline survey, 225 participated in the follow-up study 6 years later (follow-up rate: 50.2%). aBMD at the forearm was measured using dual-energy X-ray absorptiometry. aBMD values in pre-pubertal children at baseline showed a significant tracking correlation with aBMD obtained at 6-year follow-up in both genders (boys r = 0.655, girls r = 0.759). Although boys and girls in the lowest quartile of aBMD pre-pubertally had greater annual increases in aBMD from pre-puberty to 6-year follow-up than those in other aBMD quartiles, they still showed the lowest mean aBMD at 6-year follow-up. Children with lower pre-pubertal aBMD showed greater increases in BMD up until 6-year follow-up, but the increase was not great enough to catch up with other children. About 50% of the variance in aBMD at 6-year follow-up was determined by the aBMD achieved during the pre-pubertal period. Activities that increase aBMD are important not only for children during puberty, but also for younger pre-pubertal children.

Cumulative statistical power for hierarchical comparisons to evaluate two combination drug doses.

According to the regulatory requirements for multiple-dose factorial designs, a combination drug must have confirmatory evidence for being more effective than each component drug alone. An incomplete factorial design may be employed to evaluate some combination drugs because of resource constraints and priorities. In this paper, we compare the powers for four different patterns of sample size allocations in two incomplete factorial designs, with two combination drug doses and fixed total sample size. A hierarchical closed testing procedure is employed for the treatment comparisons of interest as a method to control type I error for multiple comparisons. The overall cumulative powers of contradicting all null hypotheses at a particular stage of the hierarchy and all preceding stages are determined by simulation for the respective stages of the hierarchy. The purpose is to identify the allocation of sample size so as to enable better power in a hierarchical evaluation of comparisons.