Too little sleep could be damaging to men's fertility by slashing their sperm counts, new research shows.
Scientists found sperm numbers dropped by more than a quarter in men not getting a full night's rest due to late nights, insomnia and broken sleep. Alarmingly, it even made their testicles shrink, the study found.
Sleep loss has in the past been linked with increased risk of obesity, breast cancer and heart disease.
Experts believe the ideal amount of rest is between seven and eight hours a night.
For example, one US study showed adults getting less than six hours a night were 36 per cent more likely to suffer a heart attack and 22 per cent more at risk of a stroke than those who got a full seven or eight hours.