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Frequencies and circumstances of falls were assessed among 1030 middle-aged and elderly people who participated in the NILS-LSA (National Institute for Longevity Sciences, Longitudinal Study of Aging) from November, 1997 to March, 1999 and responded to the questionnaires. The variables analyzed in the present study were demography and history of falls in the past one year. Circumstances of falls, e.g. time, location, activities associated with falls, cause of falls and degree of injury due to falls were asked when the subjects experienced a fall. Fear of falling was also investigated in all subjects. The prevalence of falls was 12.9% in the middle-aged group (40-59 yr.) and 16.5% in the elderly group (60-79 yr.). The distribution of time, location, activity associated with falls, cause and injury due to falls corresponded with previous fall studies among community-dwelling elderly people. The incidence of falls was extremely high during the daytime and outdoors. Falls occurred most frequently while walking. The majority of falls were due to extrinsic factors. About 40% of all falls caused no injury. As to the fear of falling, about 30% of the middle-aged subjects and about 60% of the elderly subjects reported that they were fearful. Our results suggested that fall accidents are not rare, even in middle-aged people.

To clarify age-related changes in bone mineral density (BMD) by peripheral quantitative computed tomography (pQCT), 1,124 Japanese middle-aged and elderly community-dwelling people were examined. The BMD of the trabecular bone was assessed at the distal part of the radius (D50), and the BMD of the cortical bone was assessed at the diaphysis of the radius (P100). P100 during age 40 to 49 was significantly higher in females (1359.6 +/- 10.7 mg/cm3, mean +/- SE) than in males (1253.5 +/- 9.5 mg/cm3), while there was no difference in D50, 245.3 +/- 5.1 mg/cm3 in females and 293.0 +/- 5.5 mg/cm3 in males. Females and males aged 50 to 59 lost 8.09 +/- 2.08 (mean +/- SE) mg/cm3 and 3.80 +/- 1.77 mg/cm3 of D50 every year, respectively. As for P100, females lost 25.1 +/- 4.48 mg/cm3, and males lost 6.37 +/- 3.89 mg/cm3 every year. Because of these gender differences, both D50 and P100 were significantly higher in males than in females aged 50 and over. Assuming that the average BMD between ages 40 and 44 was the maximum bone mineral density (BMD max), the percentage change from the BMD max with age was examined. Females aged 60 to 69 whose BMD were under 70% of the BMD max made up 73.9% in D50 and 23.2% in P100. Only 21.1% of males aged 60 to 69 showed less than 70% of the BMD max in D50 and only 3.8% in P100. The percentage decrease in BMD by age was larger in D50 than in P100 in both males and females. The individual difference in BMD was larger in D50 than in P100. These results suggest that pQCT may be useful to independently assess aging effects on cortical and trabecular bone density.

Air displacement plethysmography (ADP) is a method for the determining percent body fat (%BF) using the two-compartment model, in which the body is partitioned into body-fat mass and fat-free mass (FFM). Although this model assumes a constant density of FFM as 1.10 g/ml, its density may depend upon the bone mineral content (BMC) and total body water (TBW) which vary with age, gender, and race/ethnicity. This study compared %BF determined from ADP (ADP%BF) with %BF obtained by dual-energy x-ray absorptiometry (DXA%BF), and also investigated the effects of BMC, TBW, and other factors on its value. The subjects were 721 female and male Japanese aged 40 to 79 years. Body density was measured by ADP and %BF was calculated using Brozek et al's equation. BMC and body-fat volume were measured using DXA, and TBW was measured by multifrequency bioelectrical impedance. A series of anthropometric measurements was taken. Although ADP%BF was highly correlated with DXA%BF (female: r = 0.89, male: r = 0.90) (p < 0.001), ADP%BF differed significantly from DXA%BF (female: -1.30 +/- 0.14% (mean +/- s.e.m.), male: 1.22 +/- 0.13%) (p < 0.001). The difference in %BF (ADP%BF-DXA%BF) was negatively associated with BMC/FFM but not with TBW/FFM in both genders. The difference in %BF was also positively correlated with waist circumference. Considering previous studies, this result may be explained by the underestimation of DXA%BF, rather than by the overestimation of ADP%BF. In conclusion, ADP may be a useful method to measure %BF. However, BMC should be taken into consideration. Furthermore, DXA%BF may be underestimated in people with large waists.

To prevent a decline in gait with age, it is necessary to investigate age-related changes in gait performance and detect related factors. The purpose of this study was to assess the association between gait ability and leg extension power among middle-aged and elderly people. Height, weight, maximum gait velocity (MGV) and leg extension power (LEP) were measured in 752 males and females who participated in the National Institute for Longevity Sciences, Longitudinal Study of Aging (NILS-LSA). Age-related changes in MGV and LEP and the association between MGV and LEP were assessed. There were significant decline trends in height, weight, MGV and LEP with advancing age (p < 0.001). MGV showed a significantly positive correlation with LEP (in males: r = 0.48 p < 0.001, in females: r = 0.47; p < 0.001). Subjects aged 60 yrs and over showed a significantly higher correlation than those under 60 yrs in males, but not in females, after adjustment for height and weight. Although the relationships between MGV and LEP were different by age and gender, LEP may be one of the important factors in maintaining gait ability.