Abstract
Aim: Bone turnover is a well studied phenomenon, however it is still unclear as to whether bone shows a season driven rhythm over the course of the year, particularly in ethnic groups. Some studies have found a significant seasonal variation in bone resorption markers but others have not. This study aimed to establish if bone turnover shows significant seasonal variation as this has practical implications in terms of the use of bone markers in diagnostics. Method: The D-FINES study (Vitamin D, Food Intake, Nutrition and Exposure to Sunlight in Southern England) investigated 373 Surrey Caucasian (C) and Asian (A) women every season over a 12 month period (2006-2007). A random sub-sample of premenopausal C (n 18) and postmenopausal C (n 17); premenopausal A (n 13) and postmenopausal A (n 17) with blood samples for all seasons were selected. Serum C-telopeptide (sCTX) was determined by electrochemiluminescent immunoassay on a cobas e411 automated analyser (Roche Diagnostics). Results: As shown in the Figure above, a mixed between-within subjects ANOVA showed there was no significant main effect of season F(3,59.0)=1.467, p=0.233. However, there was a significant between subjects effect of group F(3,61)=3.099, p=0.033, with post hoc tests showing significant differences between the two C groups (p=0.007) and between the postmenopausal A and premenopausal C groups (p=0.042) but no significant differences between the other groups. Last, there was no significant interaction between season and group F(9,143.741)=0.540, p=0.843. The lower sCTX in the younger premenopausal groups is as would be expected. However, unexpectedly, there was a non-significant trend in the postmenopausal groups for the A women to have a lower mean sCTX than the C women. In contrast, in the premenopausal women, the sCTX was lower in the C group. Therefore it appears that it is menopausal status, not ethnicity which is likely the main reason for the group differences. Indeed, there was no significant difference between ethnic groups of the same menopausal status. Conclusions: Overall, no evidence for a seasonal variation in bone resorption was found here but there was evidence for a menopausal difference in bone resorption. However, numbers of participants in this preliminary analysis was small, and the trend for an ethnic difference in the postmenopausal women might be statistically significant with higher subject numbers. Further analysis with a larger sample is planned.