Watching TV for too long 'cuts male fertility by half'

Young men who watch TV for just three hours a day have nearly half the sperm count than those rarely found in front of the box, researchers warn.

According to a new study led by Harvard School of Public Health (HSPH), men's sperm quality may be significantly affected by their levels of physical activity. Researchers found that healthy young men who were sedentary, as measured by hours of TV viewing, had significantly lower sperm counts than those who were the most physically active.

"We know very little about how lifestyle may impact semen quality and male fertility in general so identifying two potentially modifiable factors that appear to have such a big impact on sperm counts is truly exciting," said lead researcher Audrey Gaskins, a doctoral student at HSPH.

Gaskins and her colleagues analysed the semen quality of 189 men between the ages of 18 to 22 participating in the Rochester Young Men's Study during 2009 at the University of Rochester.

The men were asked about their physical activity and TV-watching habits, in addition to health issues that may affect their sperm quality, such as diet, stress levels, and smoking.

"Results showed that men who watched more than 20 hours of TV weekly had a 44 per cent lower sperm count than those who watched almost no TV," the researchers said in a statement.

Men who exercised for 15 or more hours weekly at a moderate to vigorous rate had a 73 per cent higher sperm count than those who exercised less than 5 hours per week. Mild exercise did not affect sperm quality.

"The majority of the previous studies on physical activity and semen quality had focused on professional marathon runners and cyclists, who reach physical activity levels that most people in the world cannot match.

"We were able to examine a range of physical activity that is more relevant to men in the general population," said Jorge Chavarro, senior author of the study and assistant professor of nutrition and epidemiology at HSPH.

The study was published in the British Journal of Sports Medicine.