High Cholesterol May Diminish Ability to Conceive

Larry Hand

May 20, 2014

For the first time in humans, researchers have found a link between high cholesterol levels and diminished capacity for couples to conceive, according to a study published online May 20 in the Journal of Clinical Endocrinology & Metabolism.

Enrique F. Schisterman, PhD, from the Division of Intramural Population Health Research at the Eunice Kennedy Shriver National Institute of Child Health and Development, Rockville, Maryland, and colleagues conducted a population-based prospective cohort study involving 501 heterosexual couples attempting to have children during the period between 2005 and 2009. Researchers recruited the couples from the recently completed Longitudinal Investigation of Fertility and the Environment (LIFE) study.

The couples, residents of either Michigan or Texas, had overall mean ages of 30.0 years for women and 31.8 years for men and an overall mean body mass index of 27.6 for women and 29.8 for men. The majority of both women and men were non-Hispanic white college graduates, and 68% of the couples had an annual household income of $70,000 or more.

Researchers gathered health, demographic, and reproductive histories and information on physical activity and medication use on enrollment, and couples kept daily diaries until the women became pregnant or for 12 months while they tried to get pregnant.

Researchers instructed participants on how to use commercially available fertility monitors to check for low, high, or peak fertility, and they also trained women on how to use home pregnancy tests. Nurses obtained nonfasting blood samples for the quantification of serum lipids, and all laboratory tests were analyzed at a Centers for Disease Control and Prevention laboratory.

Researchers quantified lipids for 491 men (98.0%) and 489 women (97.6%), accounting for levels of total cholesterol, free cholesterol, phospholipids, triglycerides, and total lipids. They divided the participants into quartiles based on free cholesterol levels.

Significant Association

Of the 501 couples enrolled, 347 (69%) developed a pregnancy within a year and 54 (11%) did not; 100 couples (20%) withdrew from the study. Researchers found that older age was significantly associated with higher cholesterol levels in both women (P = .0005) and men (P = .0008) in the highest quartiles (women older than 51 years and men older than 57 years). They also found a higher percentage of Hispanic men in the high quartile of free cholesterol levels.

They found that free cholesterol levels in women and men were significantly higher among couples who did not develop pregnancies within a year (women: 44 mg/dL pregnant, 46 ng/dL not pregnant [P = .04]; men: 48 ng/dL pregnant, 52 ng/dL not pregnant [P = .009]). Men, but not women, in couples that were not pregnant also had higher total cholesterol levels (198 mg/dL; P = .002).

Monitoring Recommended

"In addition to raising the risk of cardiovascular disease, our findings suggest cholesterol may contribute to infertility," Dr. Schisterman said in a news release. "Our results suggest prospective parents may want to have their cholesterol checked to ensure their levels are in an acceptable range."

The researchers point out that although no human studies have been published linking high cholesterol to diminished fertility, animal studies have linked dyslipidemia and infertility.

The researchers conclude that "serum lipids may be associated with diminished couple fecundity and a longer" time to pregnancy. Although the mechanism is unclear, "both male and female lipid concentrations were shown to be independent predictors of couple fecundity, after accounting for the role of body adiposity. These findings are of particular relevance, given the increased prevalence of obesity and dyslipidemia worldwide, coupled with evolving data suggesting temporal declines in human fecundity."

This research was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Development. The authors have disclosed no relevant financial relationships.

J Clin Endocrinol Metab. Published online May 20, 2014. Abstract

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