Study objectives: To describe self-reported nap behavior and relationships among nap history, nap behavior during the study, indicators of subjective and objective insomnia, and self-reported daytime sleepiness from data previously obtained in a week-long field study of sleep in midlife women with and without insomnia.
Design: Descriptive/comparative secondary analysis.
Setting: Individual homes of the participants.
Participants: Midlife women (mean age 46+/-4 years) with self-reported insomnia (n=101) and women with adequate sleep (n=30).
Interventions: N/A.
Measurements and results: Sleep patterns were assessed by polysomnography (PSG), daily diaries, and a sleep history form. Although all women were requested not to nap, 47% of the women reported nap behavior during the study. Strong relationships were observed between a history of daytime naps and nap behavior (chi2 = 25.63, p < or = .001), and a history of feeling sleepy or struggling to stay awake during the daytime (i.e., sleepiness) and nap behavior (chi2 = 18.05, p < or = .001) during the study. There was also a modest significant (p < or = .05) correlation (r = .25) between tiredness and nap duration during the study. There were no statistical differences in sleep variables between the napping and non-napping groups. In the napping group, there were no differences between women with sleep efficiency < 85% (objective insomnia) and those with sleep efficiency > 85%.
Conclusions: Habitual nap behavior may be indicative of daytime sleepiness in women with insomnia, but it is not necessarily related to subjective or objective measures of insomnia. Women who routinely nap may be unable to refrain from napping during the daytime in long-term research studies.