FRIDAY, July 8, 2011 (HealthDay News) -- It is well-known that smoking is unhealthy, yet men who smoke are less likely than nonsmokers to require total hip or knee replacement, according to a new study.
The researchers also found that being overweight or doing vigorous physical activity increased the likelihood of joint replacement.
In the study, Australian researchers analyzed the medical records of 11,388 men who were followed from 1996-1999 to March 2007. During that time, 857 of the men had either total knee replacement (59 percent) or total hip replacement (41 percent).
The investigators found that being overweight independently increased the risk of total joint replacement, while smoking lowered the risk. This reduced risk was most evident after 23 years of smoking, and men who smoked 48 years or more were up to 51 percent less likely to undergo joint replacement than men who never smoked, the study showed.
The University of Adelaide researchers also found that vigorous exercise increased the risk of joint replacement in men aged 70 to 74, according to the study published in the July 8 online edition of the journal Arthritis & Rheumatism.
"Our study is the first to demonstrate a strong inverse correlation between smoking duration and risk of total joint replacement. The independent inverse associations of smoking with risk of total joint replacement were evident also after adjusting for major confounders and after accounting for the competing mortality risk in this elderly [group] of men," study author George Mnatzaganian, a Ph.D. student, said in a journal news release. "Further investigation is needed to determine how smoking impacts the development of osteoarthritis."
According to the 2007 National Hospital Discharge Survey, about 230,000 Americans had hip replacements and 543,000 had knee replacements that year. Severe osteoarthritis was the most common reason for the procedures.
The U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases has more about joint replacement.