How do reproductive and lifestyle factors influence bone density in distal and ultradistal radius of early postmenopausal women? The Nord-Trøndelag Health Survey, Norway.

In a population-based health survey, densitometry was performed at the distal and ultradistal radius with single-energy X-ray absorptiometry. Bone mineral density (BMD) data and self-reported reproductive and lifestyle data from 1652 randomly selected peri- and postmenopausal women aged 50-59 years were analyzed. A total of 893 (54.1%) postmenopausal women reported no prior use of hormone replacement therapy (HRT) and constituted the principal group of study. These women were more frequently smokers, consumed less alcohol, more coffee and had made less use of oral contraceptives (OC) than women in the HRT group. The strongest association with both distal and ultradistal radius bone densities was found for age, weight, time since menopause and a history of bilateral oophorectomy. Among reproductive factors, nulliparous women had lower BMD than parous women; however, no linear relationship was found between parity and bone density. A weak, positive relationship was found for OC and BMD in bivariate, but not in multivariate analyses. A history of hysterectomy was positively associated with BMD, stronger at the ultradistal than distal radius. A positive relationship between alcohol consumption and BMD was found at the ultradistal radius. Present or prior smokers had lower BMD than never smokers. In the multivariate model, interaction between pack-years of smoking and daily coffee intake was observed at the distal radius, and both factors had a stronger negative influence on distal than ultradistal radius bone density. In perimenopausal women, most reproductive and lifestyle risk factors found to be associated with BMD of the radius may be explained by different levels of estrogen.