Smoking has a negative impact on health. That's a well-established fact. With regard to smoking and its effect on osteoarthritis, there is contradictory evidence. Researchers have suggested smoking has a negative effect on osteoarthritis, but at least one study suggests there may be a protective effect against osteoarthritis. Let's look at the evidence.
Smoking Worsens Knee Osteoarthritis in Men
Men who have knee osteoarthritis and smoke have greater cartilage loss and more severe pain than men who do not smoke, according to study results published in the January 2007 Annals of the Rheumatic Diseases. The study, led by a Mayo Clinic rheumatologist, examined the symptomatic knees of 159 men. The men were monitored for up to 30 months. Their knees were scanned using MRI and their pain level was scored. Of the 159 men, 19 were active smokers at the beginning of the study. On average, the 19 men smoked 20 cigarettes a day for about 40 years.
The study results revealed that the smokers were more than twice as likely to have significant cartilage loss than the non-smokers. According to researchers, reasons that may explain the link between smoking and cartilage loss include:
- Smoking may disorder the cells and deter cell production in cartilage.
- Smoking may raise levels of toxins in the blood, contributing to cartilage loss.
- Smoking may increase carbon monoxide levels in the blood, affecting blood oxygenation, which could impede cartilage repair.
The smokers also had higher pain scores than the non-smokers. Since cartilage does not have pain fibers, increased pain may not be caused by cartilage loss. However, smoking may impact other structures in the knee or may have an effect on pain perception.
Smoking Protects Against Knee Osteoarthritis
According to the September 2007 issue of Osteoarthritis and Cartilage, researchers analyzed the connection between x-ray evidence of knee osteoarthritis and obesity and occupation. Unexpectedly, during that analysis, researchers found a modest protective effect of smoking on the development of osteoarthritis.
To confirm the findings, researchers also analyzed data from the Framingham Osteoarthritis Study and found that smokers had a lower rate of osteoarthritis than non-smokers. The effect of nicotine on the chondrocytes (a layer of cells) in articular cartilage may account for the protective effect.
Similarly, in an older study published in February 1989 in Arthritis & Rheumatism, while studying knee osteoarthritis in the first Health and Nutrition Examination Survey, researchers unexpectedly found a protective association between smoking and osteoarthritis after adjusting for age, sex, and weight.
Based on their own findings and the comparison with the Framingham Osteoarthritis Study, researchers concluded that smoking or some unknown or unidentified factor related to smoking modestly protects against the development of knee osteoarthritis.
The Chingford Study: Smoking and Risk of Osteoarthritis in Women
A study, published in the February 1993 Annals of the Rheumatic Diseases, looked at cigarette smoking and the risk of osteoarthritis in women in the general population. Since previous studies concluded that smoking had a protective effect against the development of knee osteoarthritis, 1,003 women from the Chingford (greater London, England) general population were studied. There were 463 women classified as ever smokers (consumed an average of 14.9 cigarettes a day for a mean of 25.7 years) and 540 non-smokers. Hand and knee x-rays were used to assess osteoarthritis. Results did not support an inverse association between smoking and osteoarthritis in women. Inverse association would mean as smoking increased, osteoarthritis decreased -- and this theory was not supported by the Chingford study.
The Clearwater Osteoarthritis Study
Yet one more study, known as the Clearwater Osteoarthritis Study, published in the January 2003 Osteoarthritis and Cartilage concluded that smoking did not appear to significantly protect against the development of osteoarthritis. The conclusion followed examination of 2505 men and women. The study participants were examined for osteoarthritis at 4 sites -- knee, hand, foot and cervical spine. Self-reported history of smoking determined smoking status.
Conclusion About Smoking and Osteoarthritis
With the well-known health hazards related to nicotine, it would be impossible to recommend smoking, even if more studies pointed to a protective effect on osteoarthritis. Researchers are far from concluding that there is any substantial benefit associated with smoking.
Cigarette smoking and the risk of cartilage loss and knee pain in men with knee osteoarthritis. Annals of the Rheumatic Diseases. S Amin et al. January 2007. Smoking and osteoarthritis: Is there an association? The Clearwater Osteoarthritis Study. Osteoarthritis and Cartilage. Wilder FW et al. January 2003. Does smoking protect against osteoarthritis? Arthritis & Rheumatism. Felson MD, David T. et al. February 1989. Cigarette smoking and risk of osteoarthritis in women in the general population: the Chingford study. Hart, DJ and Spector, TD. Annals of the Rheumatic Diseases. February 1993.
Cigarette smoking and the risk of cartilage loss and knee pain in men with knee osteoarthritis. Annals of the Rheumatic Diseases. S Amin et al. January 2007.
Smoking and osteoarthritis: Is there an association? The Clearwater Osteoarthritis Study. Osteoarthritis and Cartilage. Wilder FW et al. January 2003.
Does smoking protect against osteoarthritis? Arthritis & Rheumatism. Felson MD, David T. et al. February 1989.
Cigarette smoking and risk of osteoarthritis in women in the general population: the Chingford study. Hart, DJ and Spector, TD. Annals of the Rheumatic Diseases. February 1993.