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Guys, if your idea of fun is popping a few brewskies or smoking a few herbs in front of a big-screen TV, now might not be the time for you to plan to become fathers. However, nature may take care of that decision for you.

A paper published in the February 2013 edition of the British Journal of Sports Medicine reports the not-entirely-surprising conclusion that men who watch more TV have lower sperm counts.

Harvard doctoral student and spokesman for the researchers Audrey Gaskins is quoted by the website Med Page Today as saying that men who watched the least television per week and engaged in the most physical activity had, in the Harvard story, the highest sperm counts, and men who watched the most television and engaged in the least physical activity had the lowest sperm counts.

Men who watched television an average of 3 hours a day (20 hours per week) had sperm counts 44% lower than men who did not watch television at all.

Male Fertility Has Been a Public Health Concern for Several Decades

The Harvard study of activity and male fertility has been inspired by multiple observations that men's fertility has been on the decline all over the world since 1980, especially in the most advanced, industrialized countries. 

The most alarming studies of male fertility have come from the nation of Denmark, where, for genetic reasons, men tend to have unusually large testicles, and it is apparently relatively easy to recruit men to donate sperm samples for long-term research. (In the most recently published study, men received compensation of approximately €65 for each visit to the clinic.)

A team of researchers at the Rijkshospitalet medical center in Copenhagen collected semen samples from 4,687 men for 15 years, from 1996 to 2010.

They found that sperm counts (measured in millions of sperm per milliliter of semen) actually rose between the 1990's and 2010, from 43 to 48 million per milliliter, and total sperm count per ejaculation rose, on average, from 132 million to 151 million.

Sperm Count Not the Only Problem in Male Fertility

These figures were actually better than averages in sperm samples collected at the hospital during World War II.

However, the problem is that only 32% of all sperm are motile, that is, capable of "swimming" through the cervix to the opening of the Fallopian tube to fertilize the egg, and only 7% of all sperm are viable sperm capable of fertilizing the egg even if they reach their destination.

Just 23% of men in Denmark, which has some of the highest rates of male fertility in the world, are capable of becoming fathers in a 12-month period, even if their partners have no fertility issues.

Since medical scientists do not yet know how to enhance sperm quality in otherwise healthy men, they have to focus on sperm quantity. The Harvard study suggests that sperm quantity is greatly diminished in men whose lifestyle includes lots of hours in front of the TV, and couch potatoes are considerably less likely to impregnate their partners.

Continue reading after recommendations

  • Bankhead, C. "Low Sperm Count Tied to High TV Time," Med Page Today,, 04 February 2013, accessed 20 February 2013.
  • Gaskins AJ, Mendiola J, Afeiche M, Jørgensen N, Swan SH, Chavarro JE. Physical activity and television watching in relation to semen quality in young men. Br J Sports Med. 2013 Feb 4. [Epub ahead of print].
  • Jørgensen N, Joensen UN, Jensen TK, Jensen MB, Almstrup K, Olesen IA, Juul A, Andersson AM, Carlsen E, Petersen JH, Toppari J, Skakkebæk NE. Human semen quality in the new millennium: a prospective cross-sectional population-based study of 4867 men. BMJ Open. 2012 Jul 2. 2(4). pii: e000990. doi: 10.1136/bmjopen-2012-000990. Print 2012.
  • Photo courtesy of scion02b on Flickr: