About 25% of Americans experience acute insomnia each year, but about 75% of these individuals recover without developing persistent poor sleep or chronic insomnia, according to a study from researchers at the Perelman School of Medicine at the University of Pennsylvania that was presented at SLEEP 2018.

The new study offers the latest data on the prevalence of acute insomnia, which is characterized by difficulty falling asleep or staying asleep for as little as three nights per week for at least two consecutive weeks up to three months. Insomnia becomes chronic when it occurs at least three nights a week for more than three months.

“Whether caused by stress, illness, medications, or other factors, poor sleep is very common,” says senior author Michael Perlis, PhD, an associate professor of Psychiatry and director of the Behavioral Sleep Medicine program, in a release. “These findings reveal new insights about the paths that acute insomnia takes and can inform interventions that target poor sleep and help people recover sustained sufficient sleep.”

Although some studies have offered the prevalence of insomnia symptoms in large populations, this study offers data on transitions of good sleepers—defined as those needing fewer than 15 minutes to fall asleep and/or who spend fewer than 15 minutes awake during the night on five or more nights per week. The study specifically determines how good sleepers transition to acute insomnia, to persistent poor sleep (that is, recurring bouts of acute insomnia without sustained recovery or turning to chronic insomnia), to chronic insomnia, and how many of those affected by acute insomnia recover.

A total of 1,435 adults were recruited nationwide and tracked for one year during 2015-2017. They were verified as good sleepers over the first three months of the study and assessed on a daily, weekly, and monthly basis for one full year. The subjects kept a daily sleep diary for the duration of the study. Also, regular assessments were made regarding participants’ daytime function, stress and life events, and medical and mental health.

Among the 25% experiencing acute insomnia, about 75% of subjects recovered good sleep within 12 months, while 21% remained poor sleepers with recurring bouts of acute insomnia, and about 6% developed chronic insomnia. No significant differences were observed along racial, ethnic, or gender lines, or among people of varying incomes or body mass index.

The new data provides researchers with how many people experience acute insomnia each year, as well as how those cases progress, laying the groundwork for additional research now underway to assess what factors predict recovery (resilience) and non-recovery (persistent poor sleep or the new onset of chronic insomnia).

Previous research from the Perlis team has shown that suicides are more likely to occur after midnight than during the daytime or evening and another study showing that more sleep reduces suicide risk in those with insomnia.

This work was funded by the National Institutes of Health (R01AG041783) and by the Economic and Social Research Council (RES-061-25-0120-A).

Additional authors include lead author Amy Gencarelli, as well as Waliuddin Khader, Knashawn H. Morales, Ivan Vargas, and Jaqueline Kloss, from Penn, as well as Michael Grandner from the University of Arizona, and Jason Ellis from Northumbria University.