Men who smoke cigarettes risk doing damage to the health of their sperm, which could result in a significant decline in their ability to father children, warns a new study.1
Doctors at the University of Buffalo say sperm from nearly two-thirds of the chronic smokers failed a test they designed to measure the ability of sperm to fertilize an egg. On average, those men had a 75 percent lower likelihood of fertilization compared to nonsmokers.
"Like other cells in the body, human sperm carry a receptor for nicotine, which means they recognize and respond to nicotine," said lead researcher Loni Burkman, PhD, an associate professor and head of the Section of Andrology in the Department of Gynecology and Obstetrics at the University of Buffalo School of Medicine. "This happens because nicotine from tobacco mimics one of the most important neurochemicals produced in the body."
Sperms' Fertilizing Ability Scrutinized
Previously, Burkman and her associates reported that sperm treated with nicotine had three significant changes in their normal function, including their ability to bind to zona pellucida (ZOH-nuh peh-LEW-sihd-uh), the egg's outer covering.
In this latest study, the researchers enrolled 18 men who were heavy smokers and whose sperm quality was compared with that of men who did not smoke at all. The fertilizing capacity of sperm taken from the men in the latter group had already been confirmed.
On average, the smokers reported using at least four cigarettes per day, every day, for more than two years, and they had smoked for an average of 15 years. Using a test known as the Hemizona Assay developed by Burkman, the investigators cut the outer covering of an egg in half, placing one half with a smoker's sperm and the matching half with sperm of nonsmokers. After up to three hours of incubation, researchers counted the number of sperm tightly attached to the outside of each half.
Most Smokers' Sperm Failed
The test gives a ratio, or index, of sperm that are tightly attached to the zona pellucida. "To fail, the index must be less than 65, meaning that the smoker's sperm had less than 65% of the fertilizing capacity found in the donor," explained Burkman. "An index below 36 identifies a severe loss in fertilizing capacity."
In this test, nearly two-thirds of the sperm from smokers failed, while the remainder showed healthy function. Nearly all of those sperm that failed had an index of 36 or less, Burkman's team learned, with an average of 25.
While none of the sperm from smokers had zero fertilizing potential, "the results mean that their sperm had only 25% of the fertilizing function found in nonsmoking men," Burkman explained. "The data also showed that the men who failed were smoking about twice as many cigarettes per day, an average of 19 per day, compared to the smokers who passed the [test]."
In addition to the fact that sperm from smokers did not stay attached to eggs as well as those from nonsmokers, there are other risks to sperm caused by heavy smoking, the researchers warned. "Smoking men also should be aware that smoking can damage their sperm DNA, passing on faulty DNA to their baby," said Burkman. "Concerned smokers should quit or be tested in a local andrology laboratory."
Other Findings
This isn't the first study that warned of smoking's negative impact on sperm quality. Similar research has been conducted for more than a decade.2
In addition to reductions in sperm quality, smoking also reportedly alters male sex hormones, and can contribute to erectile dysfunction.3 A lower response to fertility treatments has also been reported.3
Last year, researchers analyzing information on nearly 4,000 patients found that cigarette smoking significantly reduced semen volume, sperm concentration, and the number of sperm with movement ability (motility), particularly when combined with alcohol consumption.
Thus, there seems to be "a synergic or additive effect of both toxic habits on male reproductive function," the researchers wrote. "Men who wish to procreate should be specifically warned of this matter."4
1. Burkman L, Mroz R, Tambar S, Beardsley S, Telesz B. The sperm form most chronic tobacco smokers exhibit a significant decline in the ability to bind to the human egg. Conjoint Meeting of the American Society for Reproductive Medicine 61st Annual Meeting and the Canadian Fertility and Andrology Society 51st Annual Meeting. 2005 Oct 15-19. Montreal, Quebec, Canada.
2. Sepaniak S, Forges T, Monnier-Barbarino P. Consequences of cigarette smoking on male fertility [Translated from French]. J Gynecol Obstet Biol Reprod (Paris) 2005 Apr;34 Spec No 1:3S102-11.
3. Peate I. The effects of smoking on the reproductive health of men. Br J Nurs 2005 Apr 14-27;14(7):362-6.
4. Martini AC, Molina RI, Estofan D, Senestrari D, Fiol de Cuneo M, Ruiz RD. Effects of alcohol and cigarette consumption on human seminal quality. Fertil Steril 2004 Aug;82(2):374-7.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
