Past and current weight change and women: the Nord-Trondelag Health forearm bone loss in middle-aged Study, Norway

Objective: The aim of this study was to investigate the association between bone loss and weight change before and concurrently to the assessment of forearm bone loss over 4.6 years in a population-based cohort of middle-aged women followed for more than 15 years. Methods: Among 8,856 women aged 45 to 60 years attending the first Nord-Trondelag Health Study study, Norway (1984-1986), a 35% random sample was invited for forearm densitometry at Nord-Trondelag Health Study 2 (1995-1997), and 2,188 women (78%) attended. After an average period of 4.6 years, they were subsequently invited for follow-up densitometry in 200 1, and 1,421 women (67.8%) met. Weight and height were measured on all three occasions. Results: During the total period of observation since baseline (15.5 y), the mean weight had increased by 3.4 kg, mostly in the youngest women. Weight loss had an accelerating and weight gain a decelerating effect on bone loss, and this was observed both for weight change occurring before the bone mineral density follow-up and for concurrent weight change. The relationship between prior weight gain or loss and bone loss seemed to persist, independent of the weight change observed during the period of bone loss assessment. Conclusions: Despite no mechanical impact of body weight on the forearm, weight loss in midlife women seems to be associated with a long-lasting negative effect on bone and vice versa for weight gain. This is presumably explained by humoral factors.