Obesity protects against osteoporosis, but the magnitude of this association has been difficult to assess from cross-sectional or short term studies. We examined the time course of bone loss as a function of body mass index (BMI) in early and late postmenopausal women. Our study population (n = 300) was a random sample of the population-based Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) Study, Finland. We excluded women without complete BMD results, premenopausal women during the second bone densitometry and women who had used hormone replacement therapy, bisphosphonates or calcitonin. BMI along with femoral neck and spinal bone mineral density (BMD) were assessed three times by dual-energy X-ray absorptiometry during a mean follow-up of 10.5 years (SD 0.5). The mean baseline age was 53.6 years (SD 2.8), time since menopause 2.9 years (SD 4.3) and BMI 27.3 kg/m(2) (SD 4.4). The data was analyzed by linear mixed models. Thus, we were able to approximate the bone loss up to 20 postmenopausal years. To illustrate, a woman with a baseline BMI of 20 kg/m(2) became osteopenic 2 (spine) and 4 (femoral neck) years after menopause, while obesity (BMI of 30 kg/m(2)) delayed the incidence of osteopenia by 5 (spine) and 9 (femoral neck) years, respectively. The delay was due to high baseline BMD of the obese, while bone loss rate was similar for both lean and obese subjects. This lean versus obese difference may also be partly due to altered X-ray attenuation due to fat mass.
In long-term prospective studies, dual-energy X-ray absorptiometry (DXA) devices need to be inevitably changed. It is essential to assess whether systematic differences will exist between measurements with the new and old device. A group of female volunteers (21–72 years) underwent anteroposterior lumbar spine L2–L4 (n = 72), proximal femur (n = 72), and total body (n = 62) measurements with the Prodigy and the iDXA scanners at the same visit. The bone mineral density (BMD) measurements with these two scanners showed a high linear association at all tested sites (r = 0.962–0.995; p < 0.0001). The average iDXA BMD values were 1.5%, 0.5%, and 0.9% higher than those of Prodigy for lumbar spine (L2–L4) (p < 0.0001), femoral neck (p = 0.048), and total hip (p < 0.0001), respectively. Total body BMD values measured with the iDXA were −1.3% lower (p < 0.0001) than those measured with the Prodigy. For total body, lumbar spine, and femoral neck, the BMD differences as measured with these two devices were independent of subject height and weight. Linear correction equations were developed to ensure comparability of BMD measurements obtained with both DXA scanners. Importantly, use of equations from previous studies would have increased the discrepancy between these particular DXA scanners, especially at hip and at spine.
We assessed the determinants of onset of hypertension in a large, prospective population-based study of perimenopausal women from the Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study. The data collection started in 1989, when a baseline postal inquiry was sent to all women aged 47-56 years (n ¼ 14 220) residing in the Kuopio Province in Eastern Finland. Names, social security numbers and addresses were obtained from the Population Register Centre of Finland. A total of 11 798 women responded at baseline and at 5-year follow-up in 1994. After the exclusion of 1777 women with prevalent hypertension at baseline and women with missing height or weight information, the study population consisted of 9485 without established hypertension at baseline. New cases of established hypertension during the follow-up (n ¼ 908) were ascertained with the Registry of Specially Refunded Drugs of the Finnish Social Insurance Institution (SII). According to the National Health Insurance, the SII granted 90% reimbursement for drug costs in defined chronic illnesses necessitating continuous medication, like arterial hypertension. Weight and weight gain both raised the risk by 5% per kg (Po0.001). Weight gain of 4-6 kg increased the risk of hypertension 1.25 times and a gain of more than 7 kg 1.65 times compared with the control (zero) group. To conclude, the onset of hypertension in peri-and early postmenopausal women was related to an increase in body weight despite controlling for initial body weight, reported physical activity and use of HRT. Therefore, preventing weight gain by dietary means and exercise is of great importance at menopausal age.
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