Objective
We sought to evaluate the impact of short sleep duration (SSD) and frequent snoring (FS) on glucose metabolism during pregnancy.
Study Design
We conducted a prospective cohort study of healthy nulliparas who participated in a sleep survey study. SSD was defined as <7 hours of sleep per night and FS, as snoring ≥3 nights per week. Outcomes included 1-hour oral glucose tolerance results and the presence of gestational diabetes mellitus (GDM). Univariate and multivariate analyses were performed.
Results
A total of 189 women participated; 48% reported an SSD and 18.5% reported FS. SSD and FS were associated with higher oral glucose tolerance values: SSD (116 ± 31 vs 105 ± 23; P = .008) and FS (118 ± 34 vs 108 ± 25; P = .04). Both SSD (10.2% vs 1.1%; P = .008) and FS (14.3% vs 3.3%; P = .009) were associated with a higher incidence of GDM. Even after controlling for potential confounders, SSD and FS remained associated with GDM.
Conclusion
SSD and FS are associated with glucose intolerance in pregnancy.
Numerous studies have demonstrated associations between abnormal sleep patterns and a wide spectrum of medical conditions. In particular, poor sleep has been linked to insulin resistance, glucose intolerance, and type 2 diabetes. The 2 sleep disorders that have been most consistently associated with abnormal glucose metabolism are short sleep duration (SSD) and sleep disordered breathing (SDB).
SSD has a variety of definitions, although most commonly it is defined as sleeping on average <7 hours per night. According to recent data from the 2004-2007 National Health Interview Survey, >28% of the US adult population sleeps <7 hours per night. SDB is a chronic condition characterized by repeated episodes of hypopnea and apnea during sleep. It is estimated that approximately 7% of adults in the general population have SDB of moderate to severe severity. Frequent snoring (FS) is a common self-reported measure of SDB. In nonpregnant adults, laboratory studies have shown that SSD and SDB are associated with impairments in glucose metabolism, and epidemiologic studies have demonstrated a link between these 2 sleep disorders and the risk of developing diabetes.
While studies have shown that SSD and FS are common complaints among pregnant women, there are limited data regarding the relationship between these sleep disturbances and glucose metabolism during pregnancy. Abnormal glucose metabolism during pregnancy is associated with adverse maternal and neonatal outcomes. If SSD and SDB during pregnancy contribute to maternal glucose intolerance, screening for and treating these sleep disorders during pregnancy may lessen maternal glucose intolerance and perhaps improve pregnancy outcomes. The objective of this study was to evaluate the impact of self-reported SSD and SDB symptoms on glucose metabolism during pregnancy.
Materials and Methods
This study was a planned secondary analysis of data from a prospective, observational study designed to evaluate the prevalence of and trends in sleep disturbances across pregnancy. The study was approved by the institutional review board of Northwestern University, Chicago, IL. Patients were recruited in the outpatient setting from among women who received care at Northwestern Memorial Hospital affiliated practices. These practices serve women who have both government-based and private health insurance. Women were approached for participation if they were nulliparous and had a singleton gestation. Women with the following medical conditions were excluded: chronic hypertension, heart disease, chronic lung disease, pregestational diabetes mellitus (GDM), chronic renal disease, and autoimmune disease (excluding treated hypothyroidism). Women who were eligible and agreed to participate provided informed consent.
The population was derived as a convenience sample (ie, nonprobability sampling, the patients are selected, in part or in whole, at the convenience of the researcher). Study participants were asked to complete a sleep questionnaire in early pregnancy (6-20 weeks) and then again in the third trimester (28-40 weeks). This questionnaire included demographic information such as maternal age, race/ethnicity, and prepregnancy weight. Subjects were followed prospectively and pregnancy outcomes were abstracted from the medical record by study personnel. Obstetric health care providers as well as study personnel who abstracted the medical record were not aware of the results of the sleep survey.
A full description of the sleep questionnaire used for this study has been reported elsewhere. The questionnaire included items that addressed sleep duration and SDB symptoms. Participants were asked “During the past month, how many hours of actual sleep did you get at night?” The questionnaire specified that this number may be different than the number of hours spent in bed. SSD was defined as sleeping <7 hours per night. Participants were also asked if they snored (self-report). If they reported snoring they were asked to choose one of the following snoring frequencies: nearly every day, 3-4 nights per week, 1-2 nights per week, 1-2 nights per month, or never/nearly never. FS, used to represent SDB, was defined as snoring ≥3 nights per week. Outcomes in women who complained of SSD or FS while pregnant (early and/or late pregnancy) were compared to outcomes in women without these sleep complaints.
Outcomes examined included mean 1-hour oral glucose tolerance (OGT) values, 1-hour OGT values ≥130, and GDM. Results of 1-hour OGT screening were obtained from the prenatal record. At our institution this testing is performed between 24-28 weeks using a 50-g glucose load that is administered without regard to the time of the last meal, in accordance with the American College of Obstetricians and Gynecologists guidelines. Women who screened positive on the 1-hour OGT went on to do a 100-g, 3-hour OGT test. The prenatal record and delivery record were searched and the presence of GDM was based on documentation in the medical record. At the time of this study physicians at our institution utilized the diagnostic thresholds established by the National Diabetes Data Group to diagnose GDM.
Outcomes and demographic characteristics in women with and without SSD and FS were compared using the t test for continuous data, and the χ 2 and Fisher’s exact tests for categorical data. Multivariable logistic regression models were used to control for potential confounders. Covariates included in the multivariable regression models included maternal age, race/ethnicity, and prepregnancy body mass index (BMI). All tests were 2-tailed and a P value < .05 was considered statistically significant. Statistical analyses were performed using statistical software (SPSS 17.0; SPSS Inc, Chicago, IL).
Results
Of the 224 eligible women who were approached, 202 (90%) agreed to participate and completed the baseline survey. In all, 189 of these women participated in the third-trimester survey as well. The mean gestational age was 13.8 ± 3.8 and 30.0 ± 2.2 weeks at the first and second survey, respectively. Demographic characteristics of the study population, as a whole, and stratified by sleep complaints, are provided in Table 1 . Results of 1-hour OGT screening were available for 182 women. For 6 women the prenatal record only stated that the screening test was “normal,” and for 1 subject there was no documentation of a 1-hour OGT. Complete prenatal records that allowed for the ascertainment of GDM were available for 188 women.
| Demographic | All participants, n = 189 | SSD, n = 88 | No SSD, n = 95 | P value | Frequent snoring, n = 35 | No frequent snoring, n = 154 | P value |
|---|---|---|---|---|---|---|---|
| Age, y | |||||||
| Mean ± SD | 29.7 ± 5.5 | 30.6 ± 4.9 | 29.3 ± 5.7 | .1 | 30.3 ± 6.5 | 29.6 ± 5.3 | .5 |
| 18-24, n (%) | 32 (17) | 8 (9) | 20 (21) | .08 | 6 (17) | 26 (17) | .8 |
| 25-34, n (%) | 126 (67) | 65 (74) | 60 (63) | 22 (63) | 104 (67) | ||
| ≥35, n (%) | 31 (16) | 15 (17) | 15 (16) | 7 (20) | 24 (16) | ||
| Ethnoracial status | |||||||
| White, n (%) | 117 (62) | 47 (53) | 68 (72) | .02 | 20 (57) | 97 (63) | .01 |
| Black, n (%) | 28 (15) | 13 (15) | 11 (11) | 11 (31) | 17 (11) | ||
| Hispanic, n (%) | 21 (11) | 16 (18) | 5 (5) | 2 (6) | 19 (12) | ||
| Other, n (%) | 23 (12) | 12 (14) | 11 (11) | 2 (6) | 21 (14) | ||
| Prepregnancy BMI | |||||||
| Mean ± SD | 24.1 ± 5.4 | 24.8 ± 5.7 | 23.4 ± 5.0 | .08 | 25.3 ± 5.1 | 23.9 ± 5.4 | .2 |
| <18.4, n (%) | 10 (5) | 3 (3) | 7 (7) | .04 | 1 (3) | 9 (6) | .3 |
| 18.5-24.9, n (%) | 119 (63) | 49 (56) | 67 (71) | 19 (54) | 100 (65) | ||
| 25-29.9, n (%) | 34 (18) | 21 (24) | 11 (12) | 7 (20) | 27 (17) | ||
| ≥30, n (%) | 26 (14) | 15 (17) | 10 (10) | 8 (23) | 18 (12) | ||
| Insurance | |||||||
| Public aid, n (%) | 36 (19) | 16 (18) | 16 (17) | .8 | 8 (23) | 28 (18) | .5 |
| Private, n (%) | 153 (81) | 72 (82) | 79 (83) | 27 (77) | 126 (82) |
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