Sons of Fathers Who Smoke Have 50 Percent Lower Sperm Counts
Although numerous studies have linked maternal smoking during pregnancy with reduced sperm counts in resulting sons, a recently published investigation from Sweden has shown that men whose fathers smoked at the time of pregnancy had half as many sperm as those with non-smoking fathers. This effect was found to be independent of nicotine usage by the mother.
Of 104 young men (age 17-20), those with fathers who smoked had a 41 percent lower sperm concentration and 51 percent fewer sperm than men with non-smoking fathers. This finding was after adjustment for the mother's own exposure to nicotine, socioeconomic factors, and the sons' own smoking. In fact, regardless of the mother's level of exposure to nicotine, the sperm count of the men whose fathers smoked was much lower.
Cotinine is a metabolite from nicotine and a marker which can be measured in the blood. By measuring the level of cotinine, the team in Lund, Sweden was able to determine whether the parents themselves smoke or whether they have been exposed to passive smoking. This is the first study to link the father's smoking habit and negative changes in the son's sperm count; however, other studies have previously shown links between fathers who smoked and various health outcomes in children, such as birth defects.
As opposed to the maternal egg cell, the father's sperm cells divide continuously throughout his reproductive lifetime and the percentage of genetically mutated sperm doubles approximately every eight years. Most newly occurring mutations come from the father and there are number of studies between advancing paternal age and a host of complex diseases. Tobacco smoke contains many substances that cause new mutations; therefore, it is certainly possible that at the time of conception, the sperm have undergone mutations and pass along genes that result in lowered sperm quality and quantity in the sons.
Amazingly, children of fathers who smoke have been reported to have up to four times as many mutations in a certain repetitive part of the DNA as children of fathers who do not smoke. Certainly additional research is necessary in regard to tobacco usage and human reproduction.
- Jonatan Axelsson, Sally Sabra, Lars Rylander, Anna Rignell-Hydbom, Christian H. Lindh, Aleksander Giwercman. Association between paternal smoking at the time of pregnancy and the semen quality in sons. PLOS ONE, 2018; 13 (11): e0207221 DOI: 10.1371/journal.pone.0207221