Michael A. Grandner

Mortality associated with short sleep duration: The evidence, the possible mechanisms, and the future

This review of the scientific literature examines the widely observed relationship between sleep duration and mortality. As early as 1964, data have shown that 7-h sleepers experience the lowest risks for all-cause mortality, whereas those at the shortest and longest sleep durations have significantly higher mortality risks. Numerous follow-up studies from around the world (e.g., Japan, Israel, Sweden, Finland, the United Kingdom) show similar relationships. We discuss possible mechanisms, including cardiovascular disease, obesity, physiologic stress, immunity, and socioeconomic status. We put forth a social-ecological framework to explore five possible pathways for the relationship between sleep duration and mortality, and we conclude with a four-point agenda for future research.

Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society.

ABSTRACT Sleep is essential for optimal health. The American Academy of Sleep Medicine (AASM) and Sleep Research Society (SRS) developed a consensus recommendation for the amount of sleep needed to promote optimal health in adults, using a modified RAND Appropriateness Method process. The recommendation is summarized here. A manuscript detailing the conference proceedings and evidence supporting the final recommendation statement will be published in SLEEP and the Journal of Clinical Sleep Medicine.

Sleep disturbance is associated with cardiovascular and metabolic disorders

Existing research has demonstrated associations between sleep duration and obesity, diabetes, cardiovascular disease and mortality. Sleep disorders research has shown that sleep apnoea, insomnia and other sleep disorders confer risk for cardiometabolic disease, particularly in the presence of reduced sleep duration. The aim of the present study was to examine the associations between general sleep disturbance, operationalized as ‘difficulty falling asleep, staying asleep, or sleeping too much’ as measured in a large, nationally representative sample, and self‐reported history of myocardial infarction, stroke, coronary artery disease, diabetes and obesity. Data from the Behavioral Risk Factor Surveillance System were analysed. Complete data were available for 138 201 individuals. A hierarchical logistic regression analysis examined associations before and after adjustment for demographic, socioeconomic, medical and psychological factors. After adjusting for demographic, socioeconomic and health risk factors, sleep duration was associated with obesity [odds ratio (OR) = 1.18, P < 0.0005), diabetes (OR = 1.18, P < 0.005), myocardial infarction (OR = 1.36, P < 0.0005), stroke (OR = 1.22, P < 0.05) and coronary artery disease (OR = 1.59, P < 0.0005). In fully adjusted models that included physical health, significant relationships remained for obesity (OR = 1.14, P < 0.0005), myocardial infarction (OR = 1.23, P < 0.005) and coronary artery disease (OR = 1.43, P < 0.0005). Sleep disturbance is a significant risk factor for obesity, diabetes, myocardial infarction, stroke and coronary artery disease, and effects for obesity, myocardial infarction and coronary artery disease are the most robust after adjustment. This study demonstrates that sleep disturbance is a novel risk factor that is potentially modifiable. Future research should determine whether sleep intervention could reduce the cardiometabolic consequences of sleep disturbance.

Sleep duration versus sleep insufficiency as predictors of cardiometabolic health outcomes

OBJECTIVE The objective of the present study was to investigate the relationship between sleep insufficiency and sleep duration, particularly regarding negative cardiometabolic health outcomes already considered to be affected by reduced sleep time. METHODS A total of N=30,934 participants from the 2009 Behavioural Risk Factor Surveillance System (BRFSS) answered questions about their sleep duration as well as subjective feelings of sleep insufficiency. Outcomes included body mass index (BMI), obesity (BMI ≥ 30kgm(-2)) and history of hypertension, diabetes, hypercholesterolaemia, heart attack and stroke. Linear and logistic regression models examined whether cardiometabolic outcomes were associated with (1) sleep duration alone, (2) sleep insufficiency alone and (3) the combined effect of sleep duration and sleep insufficiency. RESULTS Results indicated that, when examined alone, sleep duration <5h (versus 7h) was related to BMI (B=2.716, p<0.01), obesity (B=2.080, p<0.000001), diabetes (B=3.162, p<0.000001), hypertension (B=2.703, p<0.000001), hypercholesterolaemia (B=1.922, p<0.00001), heart attack (B=4.704, p<0.000001) and stroke (B=4.558, p<0.000001), and sleep insufficiency (days per week, continuous) was related to BMI (B=0.181, p<0.01), obesity (B=1.061, p<0.000001) and hypercholesterolaemia (B=1.025, p<0.01). All of these relationships remained significant after adjustment for covariates, except for diabetes and sleep duration. Also, after adjustment, a significant relationship between insufficient sleep and hypertension emerged (B=1.039, p<0.001). When evaluated together, after adjustment for covariates, significant relationships remained between sleep duration <5h (versus 7h) and BMI (B=1.266, p<0.05), obesity (B=1.389, p<0.05), hypertension (B=1.555, p<0.01), heart attack (B=2.513, p<0.01) and stroke (B=1.807, p<0.05). It should be noted that relationships between sleep duration >9h (versus 7h) were seen for heart attack (B=1.863, p<0.001) and stroke (B=1.816, p<0.01). In these models, sleep insufficiency was associated with hypercholesterolaemia (B=1.031, p<0.01) and hypertension (B=1.027, p<0.05). CONCLUSIONS These analyses show that both sleep duration and insufficiency are related to cardiometabolic health outcomes, and that when evaluated together, both variables demonstrate unique effects.

Habitual sleep duration associated with self-reported and objectively determined cardiometabolic risk factors

BACKGROUND Self-reported short or long sleep duration has been associated with adverse cardiometabolic health outcomes in laboratory and epidemiologic studies, but interpretation of such data has been limited by methodologic issues. METHODS Adult respondents of the 2007-2008 US National Health and Nutrition Examination Survey (NHANES) were examined in a cross-sectional analysis (N=5649). Self-reported sleep duration was categorized as very short (<5 h), short (5-6 h), normal (7-8 h), or long (≥9 h). Obesity, diabetes mellitus (DM), hypertension, and hyperlipidemia were objectively assessed by self-reported history. Statistical analyses included univariate comparisons across sleep duration categories for all variables. Binary logistic regression analyses and cardiometabolic factor as outcome, with sleep duration category as predictor, were assessed with and without covariates. Observed relationships were further assessed for dependence on race/ethnicity. RESULTS In adjusted analyses, very short sleep was associated with self-reported hypertension (odds ratio [OR], 2.02, [95% confidence interval {CI},1.45-2.81]; P<0.0001), self-reported hyperlipidemia (OR, 1.96 [95% CI, 1.43-2.69]; P<0.0001), objective hyperlipidemia (OR, 1.41 [95% CI, 1.04-1.91]; P=0.03), self-reported DM (OR, 1.76 [95% CI, 1.13-2.74]; P=0.01), and objective obesity (OR, 1.53 [95% CI, 1.03-1.43]; P=0.005). Regarding short sleep (5-6 h), in adjusted analyses, elevated risk was seen for self-reported hypertension (OR, 1.22 [95% CI, 1.02-1.45]; P=0.03) self-reported obesity (OR, 1.21 [95% CI, 1.03-1.43]; P=0.02), and objective obesity (OR, 1.17 [95% CI, 1.00-1.38]; P<0.05). Regarding long sleep (≥9 h), no elevated risk was found for any outcomes. Interactions with race/ethnicity were significant for all outcomes; race/ethnicity differences in patterns of risk varied by outcome studied. In particular, the relationship between very short sleep and obesity was strongest among blacks and the relationship between short sleep and hypertension is strongest among non-Hispanic whites, blacks, and non-Mexican Hispanics/Latinos. CONCLUSIONS Short sleep duration is associated with self-reported and objectively determined adverse cardiometabolic outcomes, even after adjustment for many covariates. Also, these patterns of risk depend on race/ethnicity.

Short and Long Sleep Duration Associated with Race/Ethnicity, Sociodemographics, and Socioeconomic Position

STUDY OBJECTIVES Short and/or long sleep duration are associated with cardiometabolic disease risk and may be differentially experienced among minorities and the socioeconomically disadvantaged. The present study examined nationally representative data along multiple dimensions of race/ ethnicity and socioeconomic status. DESIGN Cross-sectional. SETTING Survey. PATIENTS OR PARTICIPANTS 2007-2008 NHANES (N = 4,850). INTERVENTIONS None. MEASUREMENTS AND RESULTS Self-reported sleep duration was classified as very short (< 5 h), short (5-6 h), normative (7-8 h) and long (≥ 9 h). Population-weighted multinomial logistic regression analyses examined race/ ethnicity, country of origin, language, income, education, health insurance, and food security, controlling for all others as well as age, sex, marital-status, and overall self-rated health. Outcome was self-reported sleep duration, relative to normative sleep duration. Blacks/African Americans were more likely than whites to report very short (OR = 2.34, P < 0.001) and short (OR = 1.85, P < 0.001) sleep. Mexican Americans reported less long sleep (OR = 0.36, P = 0.032). Other Hispanics/ Latinos reported more very short sleep (OR = 2.69, P = 0.025). Asians/ Others reported more very short (OR = 3.99, P = 0.002) and short (OR = 2.08, P = 0.002) sleep. Mexico-born adults reported less short sleep (OR = 0.63, P = 0.042). Spanish-only speakers reported less very short sleep (OR = 0.32, P = 0.030). Lower income groups reported more very short sleep versus >

Sleep duration, cardiovascular disease, and proinflammatory biomarkers

75,000. Compared to college graduates, increased very short sleep was seen among all lower education levels. Those with public insurance reported more very short (OR = 1.67, P = 0.31) and long (OR = 1.83, P = 0.011) sleep versus uninsured. Very low food security was associated with very short (OR = 1.86, P = 0.036) and short (OR = 1.44, P = 0.047) sleep. CONCLUSIONS Minority status and lower socioeconomic position were associated with shorter self-reported sleep durations.

Self-reported sleep complaints with long and short sleep: A nationally representative sample

Habitual sleep duration has been associated with cardiometabolic disease, via several mechanistic pathways, but few have been thoroughly explored. One hypothesis is that short and/or long sleep duration is associated with a proinflammatory state, which could increase risk for cardiovascular and metabolic diseases. This hypothesis has been largely explored in the context of experimental sleep deprivation studies which have attempted to demonstrate changes in proinflammatory markers following acute sleep loss in the laboratory. Despite the controlled environment available in these studies, samples tend to lack generalization to the population at large and acute sleep deprivation may not be a perfect analog for short sleep. To address these limitations, population based studies have explored associations between proinflammatory markers and habitual sleep duration. This review summarizes what is known from experimental and cross-sectional studies about the association between sleep duration, cardiovascular disease, and proinflammatory biomarkers. First, the association between sleep duration with both morbidity and mortality, with a focus on cardiovascular disease, is reviewed. Then, a brief review of the potential role of proinflammatory markers in cardiovascular disease is presented. The majority of this review details specific findings related to specific molecules, including tumor necrosis factor-α, interleukins-1, -6, and -17, C-reactive protein, coagulation molecules, cellular adhesion molecules, and visfatin. Finally, a discussion of the limitations of current studies and future directions is provided.

Sleep symptoms, race/ethnicity, and socioeconomic position.

Objective Although the problems associated with insufficient sleep have been thoroughly researched, there has been far less substantiation of problems associated with long sleep. Recent evidence shows that habitual sleep duration greater than 7 hours is associated with increased rates of mortality. This study compared the rates of sleep problems in both long and short sleepers. Methods Self-reported sleep complaints (eg, sleep onset latency, awakenings during the night, early morning awakenings, nonrestorative sleep, and daytime sleepiness) of nearly 1000 adults who participated in the National Sleep Foundation’s 2001 Sleep in America Poll, were compared with reported hours of weekday sleep. Results There are U-shaped relationships of sleep complaints with reported weekday total sleep time. More specifically, 8-hour sleepers reported less frequent symptoms than long sleepers or 7-hour sleepers. Conclusions Thus, long sleepers, as well as short sleepers, report sleep problems, focusing attention to the often-overlooked problems of the long sleeper.

Relationships among dietary nutrients and subjective sleep, objective sleep, and napping in women.

STUDY OBJECTIVES Growing evidence indicates sleep is a major public health issue. Race/ethnicity and socioeconomics may contribute to sleep problems. This study assessed whether sleep symptoms were more prevalent among minorities and/or the socioeconomically disadvantaged. DESIGN Cross-sectional. SETTING Epidemiologic survey. PATIENTS OR PARTICIPANTS 2007-2008 National Health and Nutrition Examination Survey (N = 4,081). INTERVENTIONS None. MEASUREMENTS AND RESULTS Sociodemographics included age, sex, race/ethnicity, marital status, and immigration. Socioeconomics included poverty, education, private insurance, and food insecurity. Sleep symptoms assessed were sleep latency > 30 min, difficulty falling asleep, sleep maintenance difficulties, early morning awakenings, non-restorative sleep, daytime sleepiness, snorting/gasping, and snoring. Decreased reported problems for most symptoms were found among minorities, immigrants, and lower education levels. In general, in fully adjusted models, long sleep latency was associated with female gender, being black/African American, lower education attainment, no private insurance, and food insecurity. Difficulty falling asleep, sleep maintenance difficulties, early morning awakenings, and non-restorative sleep were also associated with female gender and food insecurity. Daytime sleepiness was seen in female and divorced respondents. Snorting/gasping was more prevalent among male, other-Hispanic/Latino, and 9(th)- to 11(th)-grade-level respondents. Snoring was prevalent among male, other-Hispanic/Latino, less-educated, and food-insecure respondents. CONCLUSIONS Sleep symptoms were associated with multiple sociodemographic and economic factors, though these relationships differed by predictor and sleep outcome. Also, reports depended on question wording.