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.