About 30 - 40% of Americans experience transient insomnia at some point during a year, and about 10 - 15% have chronic insomnia.
Overall, insomnia is more common in women than men, although men are not immune from insomnia. Sleep efficiency deteriorates equally in men and women as they get older.
Hormonal fluctuations that occur during menstruation, pregnancy, and menopause put women at higher risk of insomnia. Women are also more likely than men to suffer from anxiety and depressive disorders, which can cause insomnia.
Insomnia is more common in older people than younger people. As people grow older, sleep patterns change. Elderly adults tend to wake up frequently during the night, wake up earlier, and report waking up feeling unrefreshed.
Elderly people are more likely than younger people to have medical conditions that cause pain or nighttime distress. These conditions include arthritis, gastrointestinal distress, frequent urination, lung disease, and heart conditions. Neurologic conditions, such as Parkinson’s and Alzheimer’s, can also affect sleep patterns. Consequences of poor sleep in the elderly include increased risk of falls.
Shift workers are at considerable risk for insomnia. Over half of shift workers report one or more symptoms of insomnia at least a few nights a week. Workers over age 50 and those whose shifts are always changing are particularly susceptible to insomnia, although night-shift workers also have a high rate of sleeplessness. Night-shift workers are at risk for falling asleep on the job at least once a week, implying that their internal clocks do not adjust to unusual work times. (They are also at much higher risk than other workers for automobile accidents due to their drowsiness and may also have a higher risk for health problems in general.)