OCs associated with reduced risk of MS

Findings from a new study indicate that use of oral contraceptives (OCs) may affect the development of multiple sclerosis (MS).1 While the study provides support for the concept of hormonal influences in MS, more research is needed to demonstrate that the Pill can prevent the onset of the disease.

Approximately 400,000 Americans have MS, and every week about 200 people are diagnosed with the disease, according to the National Multiple Sclerosis Society in New York City.2 A chronic, unpredictable disease of the central nervous system, MS is thought to be an autoimmune disorder. MS symptoms result when the immune system attacks myelin, the tissues surrounding the nerve fibers of the central nervous system.

Symptoms of MS are unpredictable and vary from person to person. They may include abnormal fatigue, episodes of numbness and tingling, loss of balance and muscle, slurred speech, tremors, stiffness, and bladder problems.2

MS occurs twice as often in women as in men, and attacks are less likely during pregnancy. This finding is sparking research into the possible influence of sex hormones on the disease, says Patricia O’Looney, PhD, director of biomedical research programs at the National MS Society. "Our position in the past five to six years has been to encourage research in this area, to really accelerate the interest in the scientific community in trying to find more answers."

Such advances are needed. In severe MS, people have symptoms on a permanent basis that may include partial or complete paralysis as well as difficulties with vision, cognition, speech, and elimination.2

When investigators began formulating the currently published research, there were only three studies assessing the association between OCs and MS,3-5 says Álvaro Alonso, MD, PhD, a research fellow in the department of epidemiology at Harvard University’s School of Public Health in Boston and lead author of the study.

None of them found an important link, he observes. "However, two of them had a limited sample size, and the other was not well suited to assess the short-term effect of OCs on the risk of MS, given that the information on OC is gathered every other year."

To conduct the current study, Alonso’s team analyzed women from the General Practice Research Database, which contains prospective health information on more than 3 million people in the United Kingdom who are enrolled with selected general practitioners. They identified 106 women younger than 50 years with definite or probable MS who had been followed for at least three years before the onset of symptoms and compared the records with those of 1,001 women without the disease.

Researchers found that the risk of developing MS was 40% lower in women who had used oral contraceptives, compared with nonusers, during the previous three years. In addition, women in the study showed a higher risk of developing first symptoms of MS in the six months following a pregnancy.

"From the preventive point of view, it would be worthy to study the specific association of different types of OCs on the risk of MS," says Alonso. "Our number of MS cases was not large enough to study separately different OCs."

Explore the differences

Understanding the increased incidence and prevalence of MS in women compared to men, along with differences in disease course and manifestations, can provide new information about MS, its cause, and even its treatment, says O’Looney.

Prior to 1998, the National MS Society supported fewer than five research and training grants with a gender focus; however by 2003, such projects accounted for some $6.6 million in total expenditures, a 10-fold increase over pre-targeted funding. The society is cofunding projects with the National Institute of Allergy and Infectious Diseases to further look at sex differences in disease course, the immune system, brain tissues, hormonal influences, and response to infection.

One example of gender-focused research comes from Rhonda Voskuhl, MD, an associate professor in the department of neurology at the University of California at Los Angeles. In a small-scale, early-phase trial of the hormone estriol, Voskuhl’s team report that women with relapsing-remitting MS showed decreases in brain lesion activity and immune responses during treatment.6 A larger study of the subject is planned, says O’Looney.

"The MS Society has always had interest in trying to understand why women develop the disease more frequently," states O’Looney. "It wasn’t until we knew a little bit more about the immune system that we could try and tease away the differences that the hormones may play."

References

  1. Alonso A, Jick SS, Olek MJ, et al. Recent use of oral contraceptives and the risk of multiple sclerosis. Arch Neurol 2005; 62:1,362-1,365.
  2. National Multiple Sclerosis Society. What Is Multiple Sclerosis? Accessed at: www.nationalmssociety.org/MStheDisease.asp.
  3. Villard-Mackintosh L, Vessey MP. Oral contraceptives and reproductive factors in multiple sclerosis incidence. Contraception 1993; 47:161-168.
  4. Thorogood M, Hannaford PC. The influence of oral contraceptives on the risk of multiple sclerosis. Br J Obstet Gynaecol 1998;105:1,296-1,299.
  5. Hernán MA, Hohol MJ, Olek MJ, et al. Oral contraceptives and the incidence of multiple sclerosis. Neurology 2000; 55:848-854.
  6. Sicotte NL, Liva SM, Klutch R, et al. Treatment of multiple sclerosis with the pregnancy hormone estriol. Ann Neurol 2002; 52:421-428.