The consequences of insomnia can be much more serious than simple daytime sleepiness. Experts associate it with high blood pressure, heart failure, diabetes and other diseases. Lack of sleep can also lead to lower testosterone levels, new research shows. A week of sleeplessness leads to a 15% decrease in the male hormone level. Low or deficient testosterone is associated with low energy, decreased libido, poor concentration and fatigue. Testosterone is also critical for building muscle mass and strength, as well as bone density. For the purposes of the present study, scientists compared the testosterone levels of healthy young men with normal sleep patterns and those with insomnia. NEWS_MORE_BOX During the first week of the study, participants slept 8 hours each night, then three nights of 10 hours of sleep and eight nights of 5 hours of sleep. The results showed that testosterone levels decreased by 10-15% in people who experienced a week-long period of sleep deprivation compared to the rested group. This decrease in testosterone levels was also associated with a loss of vitality among the participants, the researchers said. The results were published in the Journal of the American Medical Association.