ABSTRACT
Decreased bone mineral density (BMD) with age is an increasing health problem, especially for postmenopausal women. Multiple factors have been reported to affect BMD including both genetic and environmental factors such as calcium intake and physical activity. For Thailand, people residing in different regions may differ in BMD due to these factors. However, there is a paucity of data concerning this issue. The objectives of this study were to identify the lifestyle factors which may influence BMD and to investigate the association between BMD and these factors in postmenopausal women who have been living in Bangkok and other provinces in Thailand. Subjects consisted of 466 postmenopausal women aged 46-90 years including 236 Bangkokians (116 early postmenopausals and 120 late postmenopausals) and 230 non-Bangkokians (134 early postmenopausals and 96 late postmenopausals). All were healthy and ambulatory. BMD was measured by dual energy X-ray absorptiometry (DEXA, Expert XL). Calcium intake was assessed by food-frequency questionnaire. Data were expressed by mean + /- SEM. There were 22 per cent (n=52), 5.9 per cent (n=14), and 4.2 per cent (n=10) of postmenopausal Bangkokians while 13.9 per cent (n=32), 4.3 per cent (n=10), and 2.2 per cent (n=5) of postmenopausal non-Bangkokians who had low BMD at spine, femoral neck, and at both sites, respectively. Spine BMD (SPBMD) and femoral neck BMD (FNBMD) increased significantly across the quartiles of calcium intake in both groups of subjects (P<0.05) and a significant difference was found between the lowest and the highest quartiles of calcium intake (P<0.05). Moreover, BMD at both regions was shown to be correlated with calcium intake, exercise and sunlight exposure in these subjects (P<0.001). Further analysis revealed higher BMD at spine (0.992 + 0.02 vs 0.945 +/- 0.02 g/cm2, P<0.05) and at femur (0.780 +/- 0.01 vs 0.740 +/- 0.01 g/cm2, P<0.05), calcium intake (348.9 +/- 12.7 vs 316.3 +/- 8.0 mg/day, P<0.05), exercise (2.8 +/- 0.1 vs 2.4 +/- 0.1 h/wk, P<0.001) and sunlight exposure (2.9 +/- 0.06 vs 1.9 +/- 0.04 h/day, P<0.001) were found in late postmenopausal women in other provinces than their counterparts in Bangkok. Nevertheless, no significant difference of BMD at both sites, calcium intake and exercise was found in the early postmenopausal groups of these two areas. CONCLUSIONS: There were significant differences in BMD and lifestyle factors between late postmenopausal women in Bangkok and other provinces. Environmental factors especially calcium intake, exercise and sunlight exposure, may influence BMD in late postmenopausal Thai women.