High Cholesterol Levels Linked To Lower Fertility
Cholesterol is a waxy, fat-like substance found in all cells of the body. It’s used to make a number of substances, including hormones and vitamin D. High blood cholesterol levels typically do not cause any signs or symptoms, but can increase the chances for heart disease.
According to an article published online in the Journal of Endocrinology and Metabolism (20 May 2014), high cholesterol levels may impair fertility in couples trying to achieve a pregnancy. Couples in which each partner had a high cholesterol level took the longest time to reach pregnancy. Moreover, couples in which the woman had a high cholesterol level and the man did not, also took longer to achieve pregnancy when compared to couples in which both partners had cholesterol levels in the acceptable range.
For the current analysis, the authors studied couples who were not being treated for infertility but who were trying to conceive a child. A total of 501 couples from four counties in Michigan and 12 counties in Texas were enrolled from 2005 to 2009. The couples were part of the Longitudinal Investigation of Fertility and the Environment (LIFE) study, established to examine the relationship between fertility and exposure to environmental chemicals and lifestyle. The women taking part in the study ranged from 18 to 44 years of age, and the men were over 18. The couples were followed until pregnancy or for up to one year of trying.
Study volunteers provided blood samples, which were tested for free cholesterol. The measurement of free cholesterol is used in research and differs from the cholesterol test given in doctors’ offices. Cholesterol tests administered by physicians measure the cholesterol subtypes: HDL cholesterol, LDL cholesterol and triglycerides. For the study, the authors relied on a test to measure the total amount of cholesterol in the blood, but which did not distinguish between cholesterol subtypes. The authors theorized that blood cholesterol might be related to fertility as the body uses cholesterol to manufacture hormones like testosterone and estrogen.
For the study, the authors calculated the probability that a couple would achieve pregnancy by using a statistical measure called the fecundability odds ratio (FOR). The measure estimates couples’ probability of pregnancy each cycle, based on their serum cholesterol concentrations. Results showed that on average, those couples in which the female did not become pregnant during the study duration had the highest free cholesterol levels. In general, high free cholesterol levels were correlated with longer times to pregnancy and lower fecundability odds ratios. Couples in which the female had a high cholesterol level and the male did not also took longer to achieve pregnancy when compared to couples in which both partners had cholesterol levels in the acceptable range. In their analysis, the study authors accounted for potential racial differences, as well as differences by age, body mass index, and education. Among study participants, Hispanic males had the highest free cholesterol levels.