Current issues of ACP Journal Club are published in Annals of Internal Medicine


Etiology

Review: Smoking is associated with increased hip fracture in postmenopausal women

ACP J Club. 1998 Mar-April; 128:49. doi:10.7326/ACPJC-1998-128-2-049


Source Citation

Law MR, Hackshaw AK. A meta-analysis of cigarette smoking, bone mineral density and risk of hip fracture: recognition of a major effect. BMJ. 1997 Oct 4;315:841-6.


Abstract

Objective

To determine, using meta-analysis, whether an association exists between smoking, bone mineral density, and hip fracture according to age in women.

Data sources

Studies were identified with MEDLINE by using the terms smoking or tobacco with bone density, osteoporosis, or hip fracture and using references from relevant studies.

Study selection

Studies were selected if they assessed the incidence of bone mineral density or hip fracture in women according to smoking habit. Studies were excluded if they studied patients who had specific diseases or who started smoking late in life.

Data extraction

Data were extracted on age-adjusted bone density at the femoral neck, radius, or calcaneus; difference between mean bone density of women who smoked and those who did not smoke; incidence of hip fracture; age-adjusted relative risk (RR) for hip fracture on the basis of smoking habit; and menopausal status.

Main results

19 cohort and case-control studies were identified that reported 3889 hip fractures in mainly postmenopausal women and 29 cross-sectional studies that reported bone density in 2156 women who smoked and 9705 women who did not smoke. The average number of cigarettes smoked daily was about 15. RR for hip fracture was higher in women who smoked than in those who did not smoke, and the risk increased with age (P < 0.001). Smoking had no effect on risk for hip fracture in premenopausal women but was associated with increased risk at age 60 (RR 1.17, 95% CI 1.05 to 1.30), age 70 (RR 1.41, CI 1.29 to 1.55), age 80 (RR 1.71, CI 1.50 to 1.96), and age 90 (RR 2.08, CI 1.70 to 2.54).

RR for hip fracture was indirectly estimated by using bone density differences, and a pooled RR was 2.7 for a 1 SD decrease in femoral-neck bone density (using data from 2 cohort and 10 case-control studies). Bone density measurements were not adjusted for weight or other determinants of bone density except in 3 studies that reported only adjusted data. Indirect and direct estimates of risk for hip fracture at different ages were similar. In postmenopausal women, bone density was lower in women who smoked than in those who did not smoke and the difference increased with age (P = 0.001). With each 10-year increase in age, the bone density of women who smoked decreased by 0.14 SD (CI 0.07 to 0.21 SD; approximately 2%, CI 1% to 3%), relative to the average bone density at the onset of menopause. By age 80, bone density in women who smoked was 0.45 SD (CI 0.34 to 0.56 SD, approximately 6%) lower than those who did not smoke. The association of smoking with bone density was similar at all bone sites. In premenopausal women, bone density was similar in both groups. Among all women, 13% of hip fractures were attributable to smoking.

Conclusions

Postmenopausal women who smoke have lower bone density and an increased risk for hip fracture compared with those who do not smoke. These differences increase with age. Smoking is not associated with bone density or hip fracture in premenopausal women.

Source of funding: No external funding.

For article reprint: Not available.


Commentary

This analysis concludes that smoking is an important and treatable cause of osteoporosis in postmenopausal women. It has been estimated that, by quitting smoking, a woman will reduce her risk for hip fracture by 30% to 40%, which is almost as beneficial as receiving hormone replacement therapy or alendronate (1).

The authors conclude that smoking has no adverse bone effects in premenopausal women. However, this meta-analysis combined studies that used different methods and did not test whether these studies were too heterogeneous to pool. Thus, this conclusion should be interpreted with caution.

Smoking may increase the risk for hip fracture through decreased weight, impaired health status, and decreased neuromuscular function (2).

Women who smoke should be considered for interventions to prevent osteoporosis. Although controversy exists about the effects of hormone replacement therapy on estradiol levels in women who smoke (3), the largest prospective study to date showed that women who smoked and received hormone replacement therapy had a substantially decreased risk for fracture (4).

For women who smoke and are concerned about the risk for disability and death caused by fractures, this analysis provides physicians with another motivational tool to help these women quit smoking.

Sophie A. Jamal, MD
Steven R. Cummings, MD
University of California, San FranciscoSan Francisco, California, USA

Sophie A. Jamal, MD
University of California, San Francisco
San Francisco, California, USA

Steven R. Cummings, MD
University of California, San Francisco
San Francisco, California, USA


References

1. Cummings SR. Treatable and untreatable risk factors for hip fracture. Bone. 1996;165S-7S.

2. Cummings SR, Nevitt MC, Browner WS, et al. Risk factors for hip fracture in white women. Study of Osteoporotic Fractures Research Group N Engl J Med. 1995;332:767-3.

3. Jensen J, Christiansen C, Rødbro P. Cigarette smoking, serum estrogens, and bone loss during hormone-replacement therapy early after menopause.N Engl J Med. 1985;313:973-5.

4. Cauley JA, Seeley DG, Ensrud KE, et al. Estrogen replacement therapy and fractures in older women. Study of Osteoporotic Fractures Research Group. Ann Intern Med. 1995;122:8-16.