Somnologist Alexander Kazchenko warned that chronic insomnia is extremely dangerous to health. The doctor told me how dangerous chronic lack of sleep is. A night or two without sleep won't cause health problems if you don't engage in extreme stress when you're very tired, the doctor noted. The real danger arises when sleep problems become regular. This happens if they occur more than three times a week for three months or more. Read more in the material of Koban Chai Photo: Global Look Press / © Alexander Legki.