Sleep Measured by Subjective Reports

A notable concern with using PSG is the cost and potential burden to the subject and the investigator (Reichert et al. 2003). Furthermore, physiological sleep measures do not capture the perception of the sleep by the individual, which in many instances is as crucial as the objective data (R. Bootzin, pers. commun.). Therefore, subjective reports can be useful in detecting sleep disturbances, particularly during pregnancy. Unfortunately, studies of sleep during pregnancy use various subjective sleep assessments, which result in even more outcomes. For instance, data from a subjective survey of 100 women 38 weeks pregnant reported generalized sleep disruption in 68% of the sample (Schweiger 1972). The way the author obtained these data was by retrospective questions about their sleep during pregnancy; nothing quantitative was obtained. In a similar study (Suzuki, Dennerstein, Greenwood, Armstrong, and Satohisa 1994), 192 pregnant Japanese women in various stages of pregnancy provided subjective reports of their sleep patterns. Results indicate that 88% of the sample reported disturbed sleep from their normal experience, with most of the disturbance occurring in the third trimester. These two studies are examples of basic, nonquantitative evaluations of sleep disturbance during pregnancy. Which provided dichotomous "yes or no" outcomes; they do not provide detailed information regarding the sleep patterns of pregnant women at any given point in time.

Questionnaires continue to be the most common tool used to acquire data in sleep research (Sateia, Doghramji, Hauri, and Morin 2000). They are structured to address global measurements of sleep and demonstrate high global test-retest correlations (Sateia et al. 2000), but there are numerous questionnaires in use and they vary tremendously in their level of detail and the depth of information they acquire. The caveat that not all results are analogous is necessary to keep in mind when interpreting the take home message from these studies. One study by Mindell and Jacobson (2000) cross-sectionally questioned 127 women at one of four points during pregnancy about their sleep habits and sleep disturbances using a questionnaire devised by the authors and the Epworth Sleepiness Scale. Consistent with other studies, nighttime awakenings were the most common sleep disturbance, followed by difficulty falling asleep, longer TST and more naps by the end of pregnancy. Hedman, Pohjasvaara, Tolonen, Suhonen-Malm, and Myllyla (2002) used the Basic Nordic Sleep Questionnaire to acquire sleep information from 325 women at five different time points: prior to becoming pregnancy, once during each trimester, and again during the post partum period. Their participants report an increase in TST during the first trimester, with a decrease in the second and third trimesters. There was an effect of age on TST in that older mothers had less TST at the end of pregnancy than younger mothers. Like the data derived from other studies, late pregnancy was associated with increased nighttime awakenings and restless sleep (Hedman et al. 2002). As mentioned, the questionnaires used in research studies can vary. A study by Izci, Martin, Dundas, Liston, Calder, and Douglas (2005) examined whether snoring and sleepiness were linked in pregnancy. They used a scale to determine "refreshment" upon awakening as well as the ESS. They did confirm that sleepiness is increased in the third trimester, however, sleepiness in pregnancy is not primarily a result of snoring or breathing problems (Izci et al. 2005). The take home message from this overview of using the questionnaire method to acquire sleep data during pregnancy is that the results ultimately depend on how the question(s) is asked.

A method that is used quite often and provides somewhat comparable data to PSG is the sleep diary (Baker, Simpson, and Dawson 1997). Sleep diaries are self-reports of sleep behavior and are common in sleep research due to the convenience of administration, the minimal cost associated with the measure and ease of maintenance (Lockley, Skene, and Arendt 1999). Several studies have utilized the sleep diary in describing the sleep of pregnant women. A study examining the sleep schedules of pregnant women was conducted by Fujino, Shirata, Imanaka, Nishio, Ogita, and Park (1995). The inquiries were of bedtimes, waketimes and napping in a cohort of 1968 pregnant Japanese women and 247 age-matched nonpregnant women. They report that total sleep time did not change throughout pregnancy, but bedtimes were significantly earlier by the end of pregnancy. This is consistent with PSG studies, which indicate that pregnant women spend more time in bed, yet acquire no more total sleep. Furthermore, more pregnant women took naps than nonpregnant women (Fujino et al. 1995). Shinkoda, Matsumoto, and Park (1999) had four women complete sleep logs for a 20-week period, several weeks prior to delivery and 12 weeks postpartum. Data from the sleep diaries suggested poorer sleep efficiency and longer time spent awake after sleep onset as the third trimester progressed, but nothing was statistically significant (Shinkoda et al. 1999). The fact that the sample size was extremely small implies that power may have been extremely limited. Wolfson, Crowley, Anwer, and Bassett (2003) asked 38 women who were 27 to 40 weeks pregnant to complete a sleep diary for 7 days and a depression questionnaire (Center for Epidemiologic Studies-Depression) to see if there were differences in sleep patterns between women with higher and lower depression scores. Women with higher CES-D scores had more TST, later rise times and longer nap times than those with lower CES-D scores (third trimester). Most recently, Okun and Coussons-Read (in press) compared the sleep of 35 pregnant women seen once at the end of each trimester and a sample of 41 nonpregnant controls from 2-weeks of sleep diaries. The sleep was significantly different between the pregnant and nonpregnant groups, particularly in the third trimester. Most consistent with previous studies was the greater number of awakenings and longer WASO observed across pregnancy. In regards to how sleep changed across pregnancy, WASO was higher in the first trimester than the second trimester and greatest overall in the third trimester which is in conjunction with other data; adding to the greater sleep disturbance was that they spent more time in bed and had more nighttime awakenings by the third trimester. The studies that utilize sleep diaries make an effort to acquire data comparable to that obtained from PSG. Although no information regarding sleep stages or spectral analysis can be determined, the data do provide insight into the perception of how an individual believes she is sleeping on a daily basis. This information may be better suited to understanding how comorbid conditions or interventions affect sleep.

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