Bone mineral density of lumbar spine and its relations to biological and lifestyle factors in middle-aged and aged Japanese women (Part 2). Effects of age and menopause on bone mineral density evaluated by biochemical markers of bone metabolism

Abstract

Bone mineral density of the lumbar spine (BMD) and biochemical markers for bone turnover were examined to study the mechanisms of age-related and menopause-related bone loss. We measured BMD of the lumbar spine and serum bone alkaline phosphatase (B-AIP) and bone gla-protein (BGP) as markers of bone formation and fasting urinary creatinine-adjusted hydroxyproline (Hyp/Cr) and calcium (Ca/Cr) as those of bone resorption in 166 community-dwelling Japanese women. A highly significant positive correlation between age and each of the biochemical markers, except for Ca/Cr, was observed. This relationship was not linear. Marked elevation in the levels of the markers was found in women in their sixth decade women compared with those in their fifth. All the markers correlated inversely with the BMD and these relationships remained significant after elimination of the effect of age by partialization. When analyzing the subjects in each five-year age group, the positive correlation of Hyp/Cr with Ca/Cr was significant in the subjects aged 45 to 49 and the negative correlation of Hyp/Cr with BMD was significant in those aged 50 to 54. B-AIP correlated positively with BGP in the subjects aged between 50 and 54 and inversely with BMD in those aged between 55 and 59. These correlations were significant. Thus, intercorrelations between the markers were observed five years earlier than were correlations between the markers and BMD. Such associations appeared earlier in terms of the markers for bone resorption than in terms of the markers for bone formation.(ABSTRACT TRUNCATED AT 250 WORDS)