Sleeping too little or too much can affect a man's ability to impregnate his partner, new research suggests.
The "sweet spot" appears to be 7 to 8 hours of sleep a night, said study author Lauren Wise, a professor of epidemiology at Boston University School of Public Health.
Among the 790 couples the researchers followed, "we found both short and long sleep duration -- less than 6 hours or 9 or more per night -- were associated with a reduced probability of pregnancy," Wise said.
