Couples with high cholesterol have a harder time conceiving children, researchers reported Tuesday in what they called the first study to link fertility difficulties to the fat molecule commonly associated with cardiovascular problems.
In a study of 501 couples who were trying to conceive, the time it took for the woman to become pregnant was longest if both partners had high cholesterol in their blood. When the woman alone had high cholesterol, pregnancy was also delayed.
A man with high cholesterol did not significantly delay pregnancy if the woman’s cholesterol reading was within the normal range, according to the study, conducted by the National Institutes of Health, the University at Buffalo and Emory University in Atlanta.
Cholesterol is critical to the production of hormones such as estrogen in women and testosterone and sperm in men, said epidemiologist Enrique Schisterman, who led the study. Too much or too little cholesterol can interfere with that process, he said.
Both partners should focus on living healthy lifestyles and keeping cholesterol levels down, said Schisterman, who devoted his career to fertility research after he and his wife struggled to have children. They have one child born through in vitro fertilization and another who is adopted, he said.
The study, published online in the Journal of Clinical Endocrinology and Metabolism, should not be interpreted to mean that couples seeking to conceive should take common medications such as Lipitor that lower cholesterol, Schisterman said.
The researchers did not look at interventions, he said.
Also, measures of overall cholesterol – high-density lipoproteins (HDLs), low-density lipoproteins (LDLs) and triglycerides – that people are accustomed to receiving from their doctors were not used in the study. The researchers examined free cholesterol in the blood with a different metric.
For this study, the researchers recruited couples in Texas and Michigan from 2005 to 2009 and followed them for a year or until the woman became pregnant.
Even when controlled for other factors that have already been associated with infertility, such as a high body mass index, high cholesterol clearly proved to be an additional complication, Schisterman said.