Effect of age on some blood variables relating to bone metabolism in women

The available laboratory parameters reflecting bone metabolism are not adequate for reliable diagnosis of osteoporosis. They display a marked biological variation and are inaccurate in individual cases. Therefore precise knowledge of these variations, as upon aging in healthy people is important.

The purpose was to examine the age- and weight-related variation of some blood constituents relating to mineral metabolism and commonly used in hospital laboratories in healthy women aged over 40, and to estimate their mutual correlations and normal values in different age groups.

The study series consisted of 238 healthy Caucasian women without any diseases related to bone metabolism and aged 40-86 years, who were divided into the following age categories: 40-45, 50-55, 60-65, 70-75 and over 80 years.

Markers of bone formation, alkaline phosphatase (AP) and osteocalcin, and marker of bone resorption, tartrate resistant acid phosphatase (TrAcP), as well as parathyroid hormone, phosphorus and creatinine increased with age, whereas 25-hydroxyvitamin D and oestradiol decreased. All these parameters except calcium showed a significant age relation. Only the relation of weight versus osteocalcin and weight versus TrAcP remained significant when the effect of age was included in the multiple regression analysis or the partial correlation coefficients were examined. There was a significant correlation between serum osteocalcin and serum AP. Serum TrAcP had a significant positive correlation with serum osteocalcin and serum AP. Percentage fat mass correlated significantly with AP and TrAcP.

Our observations may be useful when these markers of bone metabolism having inadequate sensitivity and specificity, are used as a battery in the diagnosis of osteoporosis and other metabolic bone diseases and in the assessment of normality in population studies.