A new study conducted at McGill University in Montreal has found that women who use birth control pill, and in particular, those who take higher doses, have an increased risk of developing lupus.
Lupus is an autoimmune disease that affects connective tissues. Lupus most often harms the skin, heart, joints, lungs, liver, kidneys, blood vessels and nervous system. The course of the disease is unpredictable, with periods of illness, called flares, alternating with remissions.
The study, led by researcher Samy Suissa, PhD, a professor of epidemiology, evaluated more than 1.7 million women who are in the U.K. General Practice Research Database of more than 6 million people. The women who were evaluated were prescribed combined oral contraceptives which included both estrogen and progestin.
The average length of time the women were followed in the study was 8 years. Researchers found that 768 of the women had received a first-time diagnosis of lupus.
They found that use of oral contraceptives was related to an increased risk of developing the disease. “I think we have clear evidence that these pills, especially at higher doses, can increase the risk of lupus,” Dr. Suissa says.
“Women who take oral contraceptives have a 50% higher risk of having lupus than women who don’t take them,” – Samy Suissa, PhD.
But researchers do not believe that the contraceptive on its own increases the risk, he says. “We think it probably interacts with some genetic predisposition.”
However, Dr. Suissa says the risk is still small.
Dr. Suissa’s team determined that the risk is higher in women who take higher dosage pills with 50 micrograms of estrogen or more compared to those who took 30 micrograms or less.
Women who took the highest dose pills had a 190% increased risk of developing lupus, while those who took the lowest had a 40% increased risk.
They also found that the risk increased by 150% in new users during the initial three months.
The results of the study were published in the April 15 issue of Arthritis & Rheumatism.