A Surprising ‘Benefit’ of Smoking

We’ve conducted diatribes against smoking on this blog for years, so the report of a new Australian study was a pleasant surprise.  It was an analysis of possible risk factors for total hip and knee joint replacement surgery.  The abstract is available online in the journal Arthritis & Rheumatism.

This was a study of 11,388 men who were part of the Health in Men Study, and enrolled in 1996-1999.  Clinical and lifestyle data at entry and subsequent hospital and mortality records were analyzed for associations between smoking, body mass index (BMI), physical activity, socioeconomic status, medical conditions, and total joint replacement (hip or knee) for osteoarthritis. 

By March 2007, there were 857 total joint replacement surgeries among the original collective – 59% knee and 41% hip. Being overweight independently increased the risk of such surgeries, while smoking lowered the risk.  The reduced risk in smokers was evident after 23 years of smoking, and men who smoked for 48 years or more were up to 51% less likely to have joint replacement surgery than men who had never smoked. 

An additional finding in the study – that vigorous exercise increased the risk of total joint replacement in men aged 70 to 74 – clearly parallels other causes of osteoarthritis, such as weight gain.  But there’s no immediately obvious explanation for a ‘protective’ effect of long-term smoking.  (It wasn’t related to less weight gain, which was discounted in the statistical analyses.)  It’s going to be worthwhile to study the smoking effect further, to see if this could help in finding an agent that could protect against osteoarthritis.

PS No one reading this should take it as a reason to start smoking or to cancel a decision to quit.  The risks of smoking (see the first link) are much worse than the possible benefits on osteoarthritic joint disease.