Elevated lipid levels and altered semen parameters in men of couples seeking fertility care.

Elevated lipid levels may adversely impact sperm quality, raising concerns about infertility, amid the rising prevalence of cardiometabolic disease. However, evidence on associations between elevated lipid levels and semen quality parameters is limited, with the need for real-world studies. We examined this association using data from the Folic Acid and Zinc Supplementation Trial (FAZST), a double-blind, placebo-controlled, block-randomized trial from 2013 to 2017. We included 2321 males (≥18 years) in couples seeking infertility treatment who completed baseline questionnaires and provided blood and semen samples. We examined associations between elevated lipid levels, and semen volume, concentration, morphology, count, and total motility at baseline and 6 months, and DNA fragmentation at 6 months. Generalized linear and log-binomial models with inverse probability of treatment and selection weights were used to address confounding and losses to follow-up. At baseline, 1343 (57.9%) men had elevated lipid levels, with a higher likelihood of increased body mass index, comorbidity burden, and male factor infertility. In baseline-adjusted linear models, men with elevated lipid levels had reduced semen volume and altered morphology. Reductions in sperm concentration and count were observed, but they were imprecise. Similar patterns were observed at 6 months, including reduced total motility. These findings suggest that elevated lipid levels may negatively affect semen quality and fertility.