VIENNA — Use of any type of oral contraceptive for 10 years was linked with about a 40% increase in relative risk of bilateral atherosclerosis in a Belgian study of about 1,300 women.
The absolute risk of bilateral carotid plaque was about 3%, and for bilateral femoral plaque the risk was about 5% in this population. Women taking an oral contraceptive (OC) had about a 1% absolute increased risk of having bilateral plaque (either type) for each 10 years of OC use, compared with those who did not have OC exposure.
This is the first time that a possible connection between OC use and atherosclerosis has been reported, Dr. Ernst-R. Rietzschel said while presenting a poster at the annual congress of the European Society of Cardiology.
The finding was “quite a shock,” Dr. Rietzschel said in an interview. “We expected to see nothing” linked to OC use.
“There is no need for panic,” he added. The next step should be to look at other data sets that include women who used OCs to see if the finding is replicated.
The study used data collected in the Asklepios study, a longitudinal population study of cardiovascular disease in a random sample of 2,524 Belgian volunteers aged 35–55 (median age 46). Included were 1,301 women. All participants underwent bilateral vascular echography of their femoral and carotid arteries.
The prevalence of women who ever used OCs for at least 1 year was 81%, with 27% current users. The median duration of use among all women who ever used an OC was 13 years.
In a multivariate analysis that controlled for many demographic and clinical features, including age, blood pressure, obesity, diabetes, activity level, food intake, and medications used, each 10-year period of OC use was associated with a 42% increase in relative risk of bilateral carotid plaque (defined as a protrusion of more than 0.5 mm or one having an absolute thickness of more than 1.5 mm). Each 10-year period of OC use was also linked to a 34% increase in relative risk of bilateral femoral plaque. Both associations were statistically significant, reported Dr. Rietzschel, a cardiologist at the University of Ghent (Belgium).
OC use was also linked with a 28% increased relative risk of unilateral femoral plaque that was also significant, and to a 17% increased relative risk of unilateral carotid plaque that was not statistically significant.
Additional data from the women showed that serum levels of high-sensitivity C-reactive protein (hs-CRP) were significantly raised in women currently using an OC.
Among the women who did not use an OC or hormone therapy, the average hs-CRP level was 1.0 mg/L (the same level as the men in the Asklepios study). But among current OC users in the study, the average hs-CRP level was 3.5 mg/L—significantly higher. Women in the study who were currently using hormone therapy had an average hs-CRP level of 1.3 mg/L, also significantly higher than nonusers.
OC use “is a major cause of hs-CRP rise in the general population,” Dr. Rietzschel and his associates said in a second poster at the meeting. The magnitude of the CRP rise “by far exceeds other population-prevalent, noninfectious stimuli” and is much larger than the rise in CRP triggered by hormone therapy. “Future research should take this effect into account when reporting CRP data in women taking OCs,” they concluded.