A meta-analysis of published epidemiologic studies of insomnia shows that women have a risk ratio for insomnia of 1.41 compared to men. According to the authors, a risk ratio of 1.0 would indicate an equal prevalence between study groups.

The authors examined research that involved a combined study population of more than one million individuals on four continents. Nine different analyses were performed to investigate the sex difference in the risk of insomnia among different conditions, including age of participants and sample size of the studies.

Each analysis shows a higher risk ratio of insomnia among female subjects. This risk increases with age, with elderly women having the highest risk of developing insomnia.

"A female preponderance of insomnia was found among different criteria, frequencies, and durations of insomnia," the authors write. "A genuine female predisposition in the risk of insomnia indeed exists."

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