Napping in women with severe emotionalbehavioural premenstrual symptoms: Effects on symptoms and subsequent sleeping patterns

One of the most prominent symptoms of the late-luteal phase of the menstrual cycle is sleep disturbance (Moline, Broch, Zak, & Gross, 2003), and this is particularly noted among women with more severe premenstrual symptoms (Lee, Shaver, Giblin, & Woods, 1990; Mauri, Reid, & MacLean, 1988). In addition, women with more severe symptoms often experience increased daytime sleepiness during the late-luteal phase (Manber & Bootzin, 1997). Past studies have found that a daytime nap is beneficial in the general population, in that it improves subjective alertness, reaction time performance, short term memory performance, vigilance performance (Tietzel & Lack, 2001), and mood (Taub, 1976). The objective of the current study was to investigate the effects of a short mid-afternoon nap during the late-luteal phase of the menstrual cycle on sleepiness, alertness, mood, and cognitive performance among women with severe and minimal emotional/behavioural premenstrual symptoms. The effects of such a nap on subsequent sleeping patterns, was also examined. Two groups of women were included in this study; 10 women suffering from severe emotional/behavioural premenstrual symptoms and 9 women with minimal to no premenstrual symptoms. After an adaptation nocturnal sleep recording, participants first spent one night during the follicular phase, followed by two nights ('nap condition' and 'no nap condition') during the late-luteal phase sleeping in the laboratory. During the 'nap condition', participants came to the laboratory in the afternoon and attempted to take a mid-afternoon nap scheduled approximately 12 hours following the mid point of their habitual nocturnal sleep, for a maximum duration of 30 minutes. They returned to the laboratory that same night for a nocturnal sleep recording. Measures of sleepiness, alertness, mood, and cognitive performance were completed before and 30 minutes after the napping session, and the sleepiness, alertness, and mood measures were also administered at every two hours until nocturnal bedtime. The same procedure was repeated for the 'no nap condition', but instead of taking a nap, participants engaged in a quiet activity. The nap and no nap conditions were counterbalanced. Core body temperature was measured continuously during the days and nights of the follicular and late-luteal recordings, using a rectal thermometer. Results from the study indicated that women with severe emotional/behavioural premenstrual symptoms had more daytime sleepiness and less alertness than women with minimal symptoms, during the late-luteal phase of the cycle. Both groups of women were found to have a more disturbed nocturnal sleep during the late-luteal phase of the cycle compared to the follicular phase. Napping during the late-luteal phase of the menstrual cycle improved sleepiness, alertness, negative and positive mood, as well as some aspects of cognitive performance, with no significant negative effects on subsequent nocturnal sleep, and in some cases even prevented the exacerbation of symptoms. Such improvements were maintained for at least 30 minutes (cognitive performance and intensity of positive mood), 4 hours (alertness and intensity of negative mood), and 6 hours (sleepiness) after napping. In addition, although napping was found to equally benefit women with severe and minimal emotional/behavioural symptoms on most variables, women with severe symptoms had a slightly greater improvement in intensity of negative mood 30 minutes after napping. Women with severe symptoms were therefore found to benefit slightly more from napping during the late-luteal phase of the cycle compared to women with minimal symptoms. The results of this study demonstrate that a short mid-afternoon nap during the late-luteal phase of the cycle could be used to improve and prevent worsening of emotional and behavioural premenstrual symptoms. This practical and non invasive intervention could not only provide relief from symptoms on a monthly basis, but may also lead to improvements in family and social domains, mental health, and overall quality of life