Effect of Aging on Bone Mineral Content in Japanese Measured by Photon Absorption Wethod
1979 Volume 16 Issue 3 Pages 253-260
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1979 Volume 16 Issue 3 Pages 253-260
Osteoporosis characterized by the loss of bone mass is quite common in the elderly people. However the quantitative study of the loss of bone mass with aging in Japanese has not been reported so far.
Therefore, the purpose of this study is to clarify the effect of aging on the loss of bone mineral content in Japanese. Radial mineral content (RMC) in 381 Japanese patients was measured by the photon absorption method developed by Nowland-Cameron.
The coefficient of variance of this method was 1.9±1.09% in 100 times of scanning.
In the male subjects, the mean RMC was at its muximum around the age of thirties (0.68±0.016g/cm2) and then gradually decreased with aging showing its lowest value (0.52±0.040g/cm2) around the age of eighties.
In the female subjects, RMC was at its maximum around the age of forties (0.61±0.012g/cm2) and then fell rapidly after the age of fifties showing its lowest value around the age of eighties (0.42±0.024g/cm2). The loss of RMC with aging in the female subjects without fracture was significantly greater than that in the age matched male subjects.
RMC was significantly smaller in the females with fractures than that in the females without fracture.
The longitudinal study revealed that the mean rate of bone mineral loss with aging was significantly greater in the females with fractures (-20.4%/3 years) than that in the females without fracture (-8.9%/3 years).
In an attempt to clarify the influence of physical parameters such as body weight, body height and age on the RMC in the elderly patients, we have subsequently studied the correlation between the RMC and these three physical factors, respectively.
Body weight and body height had a significant positive correlation with RMC in both sexes respectively, while age had a significant negative correlation with RMC in both sexses.
Subsequently, we have calculated the partial correlation coefficient between RMC and these three parameters, respectively. Among three factors examined, the most intimately correlated factor with RMC was body weight in the males and age in the females, respectively.
Subsequently, correlation between RMC and these three parameters was studied by using multiple regression analysis.
It was found that RMC was expressed by the following formula.
Male: RMC(g/cm2)=0.443-0.04x+0.05y-0.07z
Female: RMC(g/cm2)=0.641-0.12x+0.001y+0.45z
x: age x 0.1 (year), y: body weight x 0.1 (Kg)
z: body height x 0.01 (cm)
The validity of this experimental formula was checked by the distribution pattern of the residuals obtained by reducing the theoretical RMC calculated by this formula from the actual value in the females. It was found that the distribution pattern of the residuals in the females without fracture was of normal distribution at the centre in zero, thus showing the validity of this experimental formula.
The frequency distribution of the residuals in the females with fractures was found to be significantly shifted to the negative side compared with that of the females without fracture.
In conclusion, it was clearly demonstrated that RMC in the aged females with fractures can be distinguished statistically from that in the aged females without fracture using by this experimental formula.
