Smoking and bone metabolism in elderly women

Cigarette smoking has been implicated as a risk factor for osteoporosis, In the present study, the relationship between smoking and bone mineral densi ty, calcitropic hormones, calcium absorption, and biochemical indices relat ed to bone and mineral metabolism was examined at baseline, in subjects rec ruited for an osteoporotic study. The subjects included 489 elderly women, aged 65-77 years. After exclusions (thiazide users), 54 women constituted t he smoking group and 390 women were classified as nonsmokers. The effect of frequency of smoking was also examined in this population (33 light smoker s [<1 pack/day] and 21 heavy smokers [>1 pack/day]). Adjusted mean total bo dy bone mineral density was 4% lower (0.968 +/- 0.019 vs, 1.009 +/- 0.004) and the total hip density was 6% lower (0.778 +/- 0.024 vs. 0.826 +/- 0.006 ) in heavy smokers compared with nonsmokers. At the other sites measured (s pine, midradius, femoral neck, trochanter, and Ward's triangle), a similar nonsignificant trend was observed. The adjusted mean calcium absorption cor rected for weight was lower (13%) both in light and heavy smokers compared with nonsmokers, and serum 25-hydroxyvitamin D was significantly lower (16% ) in heavy smokers than nonsmokers, Serum parathryroid hormone (PTH) was hi gher in heavy smokers, but was not significantly different from that of non smokers. A significant increase in hone remodeling markers, serum osteocalc in (4.35 +/- 0.271 vs. 3.79 +/- 0.066) and urine N-telopeptide/creatinine ( NTx/Cr) ratio (74.5 +/- 5.75 vs. 49.8 +/- 1.4) was seen in heavy smokers co mpared with nonsmokers. Those results suggest that smoking lowers bone mine ral density, and is a result of decreased calcium absorption associated wit h secondary hyperparathyroidism and increased bone resorption. (C) 2000 by Elsevier Science Inc, All rights reserved.