While lifestyle factors, such as smoking, were previously known to affect bone mass, the relative importance of smoking as a risk factor was unclear. The study conducted at the University of Melbourne is significant because of the magnitude of the effects that have been demonstrated, which suggests that some lifestyle factors are more important than was previously thought.
"This will be an important step forward in the management of osteoporosis, since the results of this study can be used to improve current approaches to preventing bone loss," says Professor John Wark, one of the main investigators in the study.
The study suggests continuing high exposure to tobacco in older smokers and greater sensitivity to smoking-induced bone loss after menopause as possible explanations for the more pronounced negative effects of tobacco on bone loss in postmenopausal women. But Professor Wark says that much remains to be learnt about how smoking is linked with osteoporosis and the risk of fractures.
Osteoporosis is the progressive thinning of bone tissue and is common among the elderly. Studies estimate that 50 year old women have an almost 60 percent chance of suffering from an osteoporosis-related fracture in the remainder of their lives. The importance of osteoporosis has been recognized nationally by the listing of musculoskeletal conditions as a national priority health area.
The upside for both younger and older women is that sporting exercise is associated with positive effects on bone density. The study stresses the importance of a healthy lifestyle when young but also the significance of continuing to be active and healthy later in life. The study also suggests that sporting activity in earlier years may be associated with residual benefits in later life. It is important to note that current sporting activity in older women seems to produce benefits particularly with regard to bone density at the hip.
"Increasing bone density and bone strength in the hip is particularly important, as older people who have a fall have a high risk of breaking their hip, as well as suffering other injuries," says Professor Wark.
"Twin studies have been very informative about the role of genetic factors in common diseases such as osteoporosis, but here they have told us a lot about the effect of common lifestyle factors on bone health and the damaging effects of cigarette smoking may well have been underestimated in the past," says Professor Wark.
"Twins are enormously valuable for this type of research, and we are deeply appreciative of their contribution," he says.
The study will be published in the September 2003 issue of the prestigious Journal of Bone and Mineral Research.