Women are more likely than men to experience back pain. What is it that makes women more susceptible? Researchers have started to look at the role female hormones may play in back pain. Studies of pregnant women suggest that hormones, especially estrogen, may have a loosening effect on the joints. This is thought to be a cause of instability in the spine–and back pain.
Some studies have suggested that women who use estrogen replacement therapy may be more likely to have back pain than those who do not. However, these studies have been inconclusive. These authors wanted to look at the relationships between estrogen use, back pain, and back function in a large group of older women.
The participants were 7,209 women from four cities in the United States. All of the women were white and over age 65. They filled out questionnaires about their estrogen use, medical history, and general health. At the beginning of the study and four years later, women were asked whether they’d had back pain during the previous year. They were also asked whether their back pain made it hard to do daily activities, such as getting in and out of a car or bending to pick something up.
Fourteen percent of the women were using estrogen replacement therapy (ERT). Another 27 percent had used it sometime in the past. Compared to women who had never used ERT, women who used estrogen were generally healthier. They were thinner and more likely to exercise. They also had healthier bones.
However, women who used ERT had more back pain than those who had never used estrogen. Women currently using estrogen were especially prone to back pain. At baseline, 53 percent of women using estrogen said they’d had moderate to severe back pain in the last year. Meanwhile, only 43 percent of women who had never used estrogen reported back pain. Four years later, back pain went down a little for both groups.
Why would women on ERT have more back pain? It’s possible that this generally healthier group is more likely to speak up about back pain. It’s also possible that older women who have back pain start ERT, mistakenly thinking their back pain has something to do with osteoporosis. Still, the authors believe the relationship is more direct; they think back pain comes from something the estrogen actually does to the spine.
Women who used ERT had more problems with daily activities due to back pain. Again, this was especially true for those using ERT at the time of the study. At baseline, 12 percent of women using estrogen said they had problems with activities due to back pain. Nine percent of women who had never used estrogen had problems due to back pain. Four years later, these numbers went up slightly for both groups. Seventeen percent of women using estrogen said they hadn’t been able to do activities for one or more days during the last year. This was true for only 13 percent of those who had never used estrogen.
Notably, women who used ERT had fewer vertebral fractures than women who had never used estrogen. This means that the increase in back pain couldn’t be explained by vertebral fractures. Lifestyle and medical history also didn’t explain the increase in back pain. Women’s age, body mass, smoking history, pregnancy, exercise habits, arthritis, and diabetes didn’t affect the relationship between ERT and back pain.
Black women seem to have less back pain than white women. Research is needed to define the relationship between ERT and back pain for this and other racial groups.
Women currently using estrogen had more back problems than women who used estrogen sometime in the past. There was no clear relationship between length of use and back problems. These results suggest that estrogen may have a short-lived effect on the spine. Certainly more research is needed to show exactly how estrogen affects the back.