Seasonal variation of bone mass indices in elderly man

Abstract

The existence of a seasonal variation of bone mass indices and other variation factors of that variation in an elderly man were studied.
The subject was only myself. The right calcaneal quantitative ultrasound (QUS) parameter as bone mass indices and body weight were measured weekly, and the number of walks were measured every day, for 7 years from the age of 56 to 63. The measured QUS parameters were the speed of sound (SOS), transmission index (TI) and osteo sono-assessment index (OSI), which was calculated mathematically from both SOS and TI. The correlation of the number of walks, the body weight or global solar radiation to OSI, TI or SOS was examined, and then a multiple linear regression analysis was performed to evaluate the strength by which global solar radiation, the number of walks and age could predict each QUS parameter. The following results were shown.
(1) Seasonal variation of QUS parameters were observed, and were associated with the seasonal variation of global solar radiation.
(2) 65% of the variation of OSI were interpreted by global solar radiation, ageing and the number of walks.
(3) The independent variables which strongly influenced TI were global solar radiation and ageing. SOS was strongly influenced by the number of walks, but was not influenced by ageing.
(4) Bone mass indices were found to be significantly associated with global solar radiation and the number of walks, with a time lag of 3 and 5 months, respectively.
The decreasing of bone mass indices associated with ageing may be suppressed by increasing sunlight exposure and the number of walks.