Sometimes clinical lore actually starts to gain some scientific credibility.

For years, health care providers who treat back pain have thought that the use of oral contraception was linked to low back pain. Many women with back pain have been told by their caregiver to stop using oral contraception. That provider would use a hushed tone because the evidence for such advice was lacking and the association between oral contraceptives and back pain was unclear. Now, the association is becoming clearer, thanks to some diligent work by scientists who keep digging to find the truth behind the lore.

In 2006, one group of scientists announced that they found a definite link between the duration of oral contraceptive use and low back pain.* The longer a woman used oral contraception, the more likely she was to have chronic low back pain. This finding is not by itself; other scientists have come to the same conclusion. However, more research is needed not only to strengthen the connection between oral contraception and low back pain, but also to understand why there is a connection.

One certain fact is that oral contraception has only been around since the early 1960s for the general public. If duration of use increases the risk of injury, then we are just beginning to see the consequences in women who are in their 50s and 60s and now have chronic back pain.

How can oral contraception cause low back pain? Well, you have to think about how the pill works. These hormones trick the body into thinking that it is pregnant; thus, no eggs will get released because "one is already in the oven." During pregnancy, the supporting ligaments of the pelvis and low back start to relax and loosen in order to allow the baby to pass through the birth canal. Relaxin is the hormone responsible for this ligamentous laxity.

That is fine if you want to have a baby. But non-pregnant women taking oral contraception also have increased levels of relaxin, which compromises the support of the joints. Loose joints are at risk for injury.

Loose joints are also thought to increase the risk of low back pain in post-menopausal women using estrogen. Even though the estrogen hormones found in hormone replacement therapy are less potent than those found in oral contraception, any extra estrogen alters the structure of the pelvis and spine, possibly by affecting relaxin levels. It's also possible that the extra estrogen interacts directly with the joints, causing them to become looser. More research is being done because both types of hormone supplementation (contraception and replacement) have been linked to an increased incidence of low back pain.

So, what is a woman to do while the scientists continue to sort this out? If you have low back pain, please avoid oral contraception and hormone replacement therapy. This clinical lore is now gaining credibility. So clearly, you want to minimize your risk for back pain. As the medical evidence continues to grow, more specific solutions for women will be uncovered.

*Reference:
Wijnhoven, H., H.Vet, H. Smit, and S. Picavet. "Hormonal and Reproductive Factors Are Associated with Chronic Low Back Pain and Chronic Upper Extremity Pain in Women-MORGEN Study." Spine 31 (2006): 1496-1502.