Men who watch more than three hours of television a day are not only at greater risk of being overweight, they’re also more likely to have lower sperm counts, new research shows.
The study, published online in the British Journal of Sports Medicine, found that healthy young men who watch TV for more than 20 hours a week have almost half the sperm count of men who watch very little TV.
But the research, conducted by Harvard School of Public Health investigators, also found men who engage in at least 15 hours of moderate to vigorous exercise every week have sperm counts that much higher than those who exercise little.
Harvard researchers said the message to men is clear: “Higher moderate-to-vigorous activity and less TV watching [are] significantly associated with higher total sperm count and sperm concentration,” they concluded.
Researchers said semen quality has deteriorated in recent decades for reasons that aren’t entirely clear. To determine if increasingly sedentary lifestyles are a contributing factor, the Harvard team studied 189 young men — between the ages of 18 to 22 in 2009-10 — from Rochester, N.Y.
The men were asked about their weekly exercise habits and how much time they spent watching television, DVDs, or videos. Investigators also tracked other factors that might affect sperm quality, including medical or reproductive health problems, diet, stress levels, and smoking.
More than half the men were not overweight and only one-quarter were smokers.
The results showed the amount of moderate to vigorous physical activity the men engaged in every week ranged from five to 14 hours, and weekly TV time varied from four to 20 hours. More physically active men tended to have a healthier diet than those who watched a lot of TV.
Men who were the most physically active — engaging in exercise for 15 or more hours a week — had a 73 percent higher sperm count than the least physically active men. The results also showed that light physical exercise made no difference to the sperm count, no matter how frequent it was.
At the same time, the Harvard researchers found TV viewing had the opposite effect: Those who watched the most — 20 or more hours a week — had a sperm count that was 44 percent lower than those who watched the least.
But unlike smoking or weight, the amount of TV viewing seemed to counteract the beneficial effects of exercise, although the researchers suggested this may be “a chance finding.”
Reduced sperm count does not necessarily mean lower fertility, only that a more physically active lifestyle may improve semen quality.
“Future studies should also evaluate the extent to which different exercise types affect semen quality as previous studies suggest that there might be opposing effects of different types of activity on semen characteristics,” the investigators concluded.
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