If you needed yet another reason to quit smoking, a new study out of Sweden found that the number of cigarettes a woman smokes a day and the number of years they smoked significantly increases the risk of rheumatoid arthritis (RA) by as much as 70%.
Researchers from the Karolinska Institutet and Karolinska University Hospital noticed that although there were a large number of case studies showing cigarette smoking is directly associated with the risk of developing RA, less attention was given the amount and duration of smoking. Even less was known about the effect of smoking cessation on the future risk of developing RA.
Rheumatoid arthritis is a chronic autoimmune disease that causes inflammation, pain and swelling of the joints and surrounding tissues. According to the Centers for Disease Control and Prevention, RA affects an estimated 1.5 million Americans.
To find out if even light smoking is associated with an increased risk of RA, and whether or not quitting will reduce the risk of RA development among smokers, they analyzed data from a Swedish mammography study, which included 34,000 women between the ages 54 and 89.
Researchers say the risk of developing RA for light or moderate smokers (1 to 7 cigarettes a day) was twice that of women who never smoked. The risk jumped to 70% for heavy smokers.
When researchers compared people who had never smoked to women who had smoked for up to 25 years, they found that the corresponding risk increased with their length of smoking.
“Stopping smoking is important for many health reasons, including the increased risk of RA for smokers,” said Daniela Di Giuseppe, who led this study. “But the clearly increased risk of developing RA, even many years after giving up, is another reason to stop smoking as soon as possible, and highlights the importance of persuading women not to start at all.”
Quitting smoking did decrease the chance of developing RA and the risk continued to diminish over time. Fifteen years after giving up, the risk of RA had decreased by a third. However, compared to people who had never smoked, this risk remained significantly higher even 15 years after their last cigarette.
While researchers say the biological role of smoking in the development of RA is unclear, they suspect it has something to do with the effect it has on the immune system. Specifically, they cite smoking as a trigger for an immune response against certain proteins, which in turn might cause arthritis.
Researchers acknowledged the limitations of the study, which included the fact that they only had data on women aged 54 to 89 years, and were unable to assess the risk of RA among younger women.
They also noted that the number of individuals who quit smoking was fairly limited, while information about smoking habits was collected only on a single occasion during the study period, leading to a possible misclassification of the exposure.
Nonetheless, they conclud that “our study indicated that even light smoking is associated with increased risk of RA for women,” and that “the clearly increased risk of RA development even among former smokers is another reason to persuade women not to start smoking.”
The results, published in the open access journal Arthritis Research & Therapy, are just the latest is a series of recent studies linking smoking to chronic pain ailments.
In December, a study at the University of Rochester of more than 5,300 patients with spinal disorders and back pain found that those who quit or never smoked had less pain than those who continued to smoke.
And a study by researchers at the University of Kentucky discovered that women who smoked heavily more than doubled their odds of experiencing chronic pain.