What Do Obesity and Birth Control Have To Do With MS?
Two new studies suggest a relationship between obesity and oral contraceptives in the development of multiple sclerosis. The first study compared people with a normal body mass index to people who were obese at the age of 20 and found that the obese people were twice as likely to develop MS. The second study suggested that women who had taken hormonal birth control pills were more likely to develop MS.
In the study that looked at the link between obesity and MS, 210 people with MS and 210 people without MS were compared. People who were obese at the age of 20 were found to be twice as likely to develop MS as those who were not obese. It was also found that the obese subjects had higher levels of a hormone called leptin and low vitamin D levels. Leptin triggers hunger and is known to cause inflammation. Researchers are suggesting that leptin’s inflammatory properties could contribute to the inflammation that causes MS. Obesity is already linked to several other diseases such as diabetes, hypertension, and high cholesterol and it is no secret that our bodies need exercise and a healthy diet to function properly. It is unclear from this study if leptin is the trigger, or it could be explained by another cause such as other health conditions, inactivity, low vitamin D levels, or an unhealthy diet consisting of foods known to trigger inflammation. Vitamin D has been shown to have a strong relationship to MS, so it could be that vitamin D is the trigger as opposed to leptin. We also already know that diet and exercise play a key role in controlling symptoms in people who have MS, so lack of exercise and a poor diet could be the reason behind the development of MS. Based on this data I would say obesity is a risk factor for MS, but more data needs to be collected before suggesting that being obese causes MS.
In the study on birth control and its link to MS, 305 women with MS were compared to 3,050 women without MS. Both groups were similar when they compared the percentage of women who used birth control pills- 29% in the MS group, and 24% in the non-MS group. They then concluded that the women who were currently taking oral contraception were 35% more likely to develop MS. They also stated that women who used oral contraception in the past, but no longer used it, were 50% more likely to develop MS. A few things make me question the results of this study. I question whether birth control does cause MS, especially because the women who only had a past history of birth control use had higher rates of developing MS than the women who were on birth control. If birth control did directly cause MS I would expect the percentage of people who developed MS to be higher in the group that was currently on birth control. MS is known to be more common in women and to typically present in a woman's 20's-30's, during her childbearing years. This is the time frame when women are most likely to be on birth control which leads me to believe that the data only shows a correlation, rather then a causation. Additionally, MS was known to be more prevalent in young women long before oral contraceptives were available and popular. There are no studies that suggest the incidence of MS increased with the invention of oral contraception. Similarly to the obesity study, the data could potentially be explained by other factors and the data suggests that the estrogen and progesterone in birth control could be a risk factor, but there is not good enough data to prove this right now.
The role of hormones such as leptin, estrogen, and progesterone in causing MS is a subject that needs to be studied more. For now the National Multiple Sclerosis Society has stated that neither study proves a cause-and-effect relationship. If you want to learn a little bit more about how to tell if research study results are good or not, you can read about it in a short lesson that I posted on my blog!1,2
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