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Fracture risk and smoking

Meta-analysis
Results
Comment

We know that smoking is bad for us in many ways, and one of the ways is to decrease bone mineral density. One meta-analysis [1] showed that women who were current smokers were at increased risk for hip fracture. A new analysis [2] extends that analysis to men, to former smokers, and looks at where we live.

Meta-analysis

The new analysis examined PubMed and EMBASE up to mid 2002 for any type of study relating to smoking and fracture that reported relative risk or odds ratio in smokers compared with non-smokers. If subjects had other major diseases they were not included. Smokers were categorised as current smokers (smoking daily), previous smokers (irrespective of when they stopped), and ever smokers, a combination of both.

The outcome was the occurrence of a fracture, with division into any fracture, or hip, wrist, or spine. Analysis was by age, gender and geographical region as well as by smoking status.

Results

Fifty-one studies with 512,000 people were included in the analysis. Current smoking was associated with higher risk of any fracture, and hip and spine fractures, but not wrist fractures. Previous smoking was associated with increased risk only of hip fracture (Table 1). Studies reporting on the amount smoked reported higher risk estimates the more cigarettes smoked. Hip fracture risk was the same in men and women, for current and previous smoking (Table 1).



Table 1: Smoking status and risk of fracture



Fracture site Smoking status
Relative risk
(95%CI)
All sites Current
1.3 (1.1 to 1.4)
Previous
1.0 (0.9 to 1.2)
Hip Current
1.4 (1.2 to 1.6)
Previous
1.2 (1.1 to 1.4)
Wrist Current
0.9 (0.5 to 1.6)
Previous
0.9 (0.7 to 1.1)
Spine Current
1.8 (1.1 to 2.8)
  Previous
no data
All sites men Current
1.6 (1.1 to 2.3)
All sites women Current
1.3 (1.1 to 1.5)
All sites men Previous
1.4 (1.1 to 1.8)
All sites women Previous
1.2 (1.1 to 1.4)


Latitude was a major influence (Figure 1). Studies in current smokers from northern Europe had a higher risk for hip fractures than those from more southerly latitudes. Studies near the equator had no increased risk, and the risk from southern Europe, the USA and Mexico showed no statistically increased risk (Figure 1).



Figure 1: Fracture risk and current smoking at different latitudes














A clinically important number of fractures may be related to smoking (Table 2). Reducing current smoking would help prevent hip and spine fractures.



Table 2: Percentage of fractures attributable to smoking at different levels of smoking in a population



Percent of fractures attributable to smoking
Percentage of current smokers
Hip
Spine
All
20
7
13
5
50
16
28
12





Comment

There is much more to this paper than meets the eye. Fascinating was the relationship with latitude, implying that exposure to sunlight and vitamin D production might be an important factor.

We should not be surprised by these findings. There is considerable evidence that smoking delays bone repair after fracture or operation, and people undergoing elective orthopaedic surgery would be well advised to stop for that reason alone. Altogether yet another reason to stop smoking and to have another holiday in the sun.

References:

  1. MR Law, AK Hackshaw. A meta-analysis of cigarette smoking, bone mineral density and risk of hip fracture: recognition of a major effect. BMJ 1997 315: 841-846.
  2. P Vestergaard, L Moskelide. Fracture risk associated with smoking: a meta-analysis. Journal of Internal Medicine 2003 254: 572-583.

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