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CME EDITOR

Nancy Saltmarsh, Editor, Preventing Chronic Disease. Disclosure: Nancy Saltmarsh has disclosed no relevant financial relationships.

CME AUTHOR

Laurie Barclay, MD. Freelance writer and reviewer, Medscape, LLC. Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.

AUTHORS

Disclosures: Laura Plantinga, ScM; Madhu N. Rao, MD; and Dean Schillinger, MD, have disclosed no relevant financial relationships.

NHANES is conducted by the Centers for Disease Control and Prevention (CDC) and consists of a standardized in-home interview followed by a physical examination at a mobile examination center. NHANES uses representative samples of noninstitutionalized US civilian residents. We limited our analysis to NHANES 2005 through 2008 adult (≥20 y) participants who responded to the sleep questionnaire and completed the examination (n = 9,848). NHANES 2005 through 2006 and 2007 through 2008 reported response rates of 77.4% and 75.4% for the examined participants, respectively. All participants gave written informed consent. The National Center for Health Statistics Research Ethics Review Board approved the protocol.

Questionnaire

Interviewers administered a questionnaire pertaining to sleep habits and sleep-related problems (www.cdc.gov/nchs/data/nhanes/nhanes_05_06/sp_slq_d.pdf), including items from 2 validated instruments: the Sleep Heart Health Study Sleep Habits Questionnaire (11) and the Functional Outcomes of Sleep Questionnaire (12). We have described individual items previously (13). Nocturia was an item on a separate kidney conditions – urology questionnaire (www.cdc.gov/nchs/data/nhanes/nhanes_05_06/sp_kiq_d.pdf). Participants self-reported demographics (age, sex, race/ethnicity), socioeconomic status and health care access (education, income, and health insurance coverage), and health status and conditions (diagnosis of diabetes, hypertension, and cardiovascular disease [CVD]; smoking and alcohol use; and depressive symptoms from the Patient Health Questionnaire-9 [PHQ-9] [14]) via questionnaire. The interviewer recorded prescription medications from the bottles provided by the participant.

Examination and laboratory measurements

Laboratory personnel performed glycohemoglobin measurements using a high-performance liquid chromatography system and assessed fasting plasma glucose concentration by a hexokinase method. Laboratory personnel also measured serum and urine creatinine by the modified kinetic method of Jaffe and urine albumin using solid-phase fluorescence immunoassay. Examination personnel recorded anthropomorphic measurements (weight and height, used to calculate body mass index [BMI]) and blood pressure (≥3 auscultatory measurements).

Sleep problems

We used inadequate sleep, sleep deprivation, daytime sleepiness, and sleeping pill use as markers of insomnia. We defined inadequate sleep as less than 7 total hours of sleep, according to National Sleep Foundation guidelines (15) (Box); we defined excess sleep as 9 or more hours per night. We defined severe sleep deprivation by sleep onset latency 5 minutes or less (16). We considered daytime sleepiness and sleeping pill use to be frequent if they were reported "often" or more (≥5 times/mo). We defined apnea by frequent self-reported apnea, snorting, or gasping, or diagnosed sleep apnea. We defined nocturia as reported urination of 2 or more times per night. We included frequent self-reported leg jerks or cramps, or diagnosed restless legs syndrome as leg symptoms (Box).

Diabetes

We defined diabetes by self-report (answer of yes to the question, "Other than during pregnancy, have you ever been told by a doctor or other health care provider that you have diabetes or sugar diabetes?") or glycohemoglobin of 6.5% or more (17). We did not include fasting plasma glucose of 126 mg/dL or more in the main definition because of the small sample of fasting morning participants (n = 4,770).

Other definitions

We defined self-reported diseases by answers of yes to the question, "Have you ever been told by a doctor or other health professional that you have [disease or condition]." We defined self-reported CVD by an answer of yes to any of coronary artery disease, angina, myocardial infarction, stroke, or congestive heart failure. We defined hypertension by self-report or by measured blood pressure of 140/90 mm Hg or higher. We defined depressive symptoms by at least 5 positive responses on the PHQ-9, along with reported functional impairment. We calculated estimated glomerular filtration rate (eGFR) according to the Modification of Diet in Renal Disease equation for isotope dilution mass spectrometry traceable creatinine (18). We defined albuminuria by a single urinary albumin:creatinine ratio of 30 mg/g or more.

We compared selected characteristics for participants with and without diabetes using χ² tests for categorical variables and t tests for continuous variables. We calculated prevalence of sleep problems by diabetes classification. We used multivariable logistic regression to obtain adjusted odds ratios (ORs) and 95% confidence intervals (CIs); covariates were chosen both for evidence of confounding and for parsimony. We performed sensitivity analyses with different definitions of diabetes among those not reporting sleeping pill use, with further covariates, and stratified by possible effect modifiers. All analyses were performed using Stata version 10.0 (StataCorp LP, College Station, Texas) to account for study design weights, strata, and primary sampling units.

Participants with diabetes were older and more likely to be non-Hispanic black, to have no high school diploma, and to be insured than those without diabetes (Table 1). Relative to their counterparts, those with diabetes were less likely to be daily smokers, drank fewer alcoholic beverages per week, and were more likely to have obesity, depression, hypertension, cardiovascular disease, albuminuria, and reduced kidney function and to use diuretics (Table 1).

Overall, 93% of the adult US population reported at least 1 of the problems examined (Table 2). Leg symptoms (41%), inadequate sleep (37%), severe sleep deprivation (29%), and nocturia (25%) were the most commonly reported problems. While frequent sleeping pill use and apnea were less commonly reported, nearly 1 in 10 reported either. Those with diabetes were more likely than those without diabetes to report multiple sleep problems (mean no. of problems, 3.1 vs 2.5; Figure).

Diabetes was associated with increased odds of inadequate sleep, frequent daytime sleepiness, restless legs symptoms, sleep apnea, and nocturia (Table 3). These associations were generally robust after adjustment for confounding factors. The magnitude of the associations of sleep apnea and, to a slightly lesser extent, inadequate sleep with diabetes was attenuated by adjustment for BMI but remained significant. The associations of diabetes with daytime sleepiness and inadequate sleep were rendered nonsignificant with the final adjustment for alcohol use.

Sensitivity analyses examining the association of sleep problems with diabetes defined only by glycohemoglobin showed similar results, except that the association between glycohemoglobin and sleep apnea was fully explained by BMI (data not shown). Results with diabetes defined by self-report, glychohemoglobin, and fasting plasma glucose were nearly identical to our primary analyses. When diabetes was examined by severity category (no diabetes, diabetes with glycohemoglobin <7.5%, diabetes with glycohemoglobin >7.5%), apnea, leg symptoms, daytime sleepiness, and nocturia (but not inadequate sleep) all showed greater odds with increasing severity in a significant, graded fashion. Diabetes duration was significantly associated with the same problems; risk increased 20% to 30% per 10 years since diagnosis.

Furthermore, the associations of diabetes with sleep problems were also similar among the subset of the population not reporting sleeping pill use (data not shown). Adjustment for other possible confounders generally did not substantially change the results: waist circumference was associated with sleep apnea (per 1-cm increase: OR, 1.03; 95% CI, 1.02-1.05), but its addition to the model did not alter the association of diabetes with apnea (OR, 1.41; 95% CI, 1.02-1.95). Similarly, the association of diabetes with nocturia was not affected by either pulse pressure (OR, 1.48; 95% CI, 1.20-1.84) or systolic blood pressure (OR, 1.48; 95% CI, 1.19-1.83). Higher income was generally associated with lower prevalence of sleep problems (with the exception of apnea, which showed the opposite association for the highest income category); however, its addition to the models did not affect the association of diabetes with sleep problems.

Stratified analyses showed that the association of sleep apnea, leg symptoms, and nocturia with diabetes was strongest among participants younger than 60 years old compared to those 60 or older (leg symptoms: OR, 1.94 vs 1.24; P = .006; apnea: OR, 3.52 vs 1.59; P < .001; and nocturia: OR, 3.09 vs 1.55; P < .001) (data not shown). The association of leg symptoms with diabetes was stronger among women than men (OR, 1.65 vs 1.28; P = .04). This effect modification by age and sex was not significant for any other sleep problem, and race/ethnicity did not modify the effect of these associations.