Is there an association between shift work and having a metabolic syndrome? Results from a population based study of 27 485 people
01 Nov 2001-Occupational and Environmental Medicine (BMJ Publishing Group)-Vol. 58, Iss: 11, pp 747-752
TL;DR: Obesity, high triglycerides, and low concentrations of HDL cholesterol seem to cluster together more often in shift workers than in day workers, which might indicate an association between shift work and the metabolic syndrome.
Abstract: Objectives—To explore how metabolic risk factors for cardiovascular disease (CVD) diVer between shift workers and day workers in a defined population. Shift work has been associated with an increased risk of CVD. Risk factors and causal pathways for this association are only partly known. Methods—A working population of 27 485 people from the Vasterbotten intervention program (VIP) has been analysed. Cross sectional data, including blood sampling and questionnaires were collected in a health survey. Results—Obesity was more prevalent among shift workers in all age strata of women, but only in two out of four age groups in men. Increased triglycerides (>1.7 mmol/l) were more common among two age groups of shift working women but not among men. Low concentrations of high density lipoprotein (HDL) cholesterol (men<0.9 and women<1.0 mmol/l) were present in the youngest age group of shift workers in both men and women. Impaired glucose tolerance was more often found among 60 year old women shift workers. Obesity and high triglycerides persisted as risk factors in shift working men and women after adjusting for age and socioeconomic factors, with an OR of 1.4 for obesity and 1.1 for high triglyceride concentrations. The relative risks for women working shifts versus days with one, two, and three metabolic variables were 1.06, 1.20, and 1.71, respectively. The corresponding relative risks for men were 0.99, 1.30, and 1.63, respectively. Conclusions—In this study, obesity, high triglycerides, and low concentrations of HDL cholesterol seem to cluster together more often in shift workers than in day workers, which might indicate an association between shift work and the metabolic syndrome. (Occup Environ Med 2001;58:747‐752)
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TL;DR: The findings demonstrate the adverse cardiometabolic implications of circadian misalignment, as occurs acutely with jet lag and chronically with shift work, on metabolic, autonomic, and endocrine predictors of obesity, diabetes, and cardiovascular risk.
Abstract: Effects of Behavioral Cycle. The effects of the behavioral cycle, independent of the circadian cycle, on leptin, glucose, insulin, epinephrine, norepinephrine, and cortisol are shown in Fig. 2, Left panels. Leptin varied significantly across the behavioral cycle, with a trough around breakfast and a peak after the last meal, coinciding with the onset of the scheduled sleep episode (P 0.001, peak-to-trough 44%). Also, both glucose and insulin varied significantly across the behavioral cycle (glucose: P 0.001, peak-to-trough 26%; insulin: P 0.001, peak-to-trough 158%), presumably the result of the timing of meals. Both epinephrine and norepinephrine varied significantly across the behavioral cycle with peaks during the wake episode and troughs during the sleep episode (epinephrine: P 0.001, peak-totrough 83%; norepinephrine: P 0.001, peak-to-trough 72%). Cortisol varied significantly across the behavioral cycle, peaking after awakening and with a trough at the onset of the scheduled sleep episode (P 0.001, peak-to-trough 38%). Effect of Circadian Cycle. The effects of the circadian cycle, independent of the behavioral cycle, on leptin, glucose, insulin, epinephrine, norepinephrine, and cortisol, are shown in Fig. 2, Right panels. Glucose had a significant endogenous circadian rhythm (P 0.018, peak-to-trough 4%), with a peak during the biological night (circadian bin 300° and 0°; equivalent to22:30– 06:30 in these subjects). Epinephrine exhibited a significant endogenous circadian rhythm (P 0.001, peak-to-trough 53%), with a peak during the biological day (circadian bin 180°; equivalent to 14:30–18:30). Cortisol had a significant endogenous circadian rhythm (P 0.001, peak-to-trough 113%), with a peak at the end of the biological night (60°; close to habitual wake time). There were no significant circadian rhythms in leptin, insulin, or norepinephrine.
1,850 citations
Cites background from "Is there an association between shi..."
...(1996) Activation of beta(3) adrenergic receptors suppresses leptin...
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...These combined effects during circadian misalignment may provide a mechanism underlying the increased risk for obesity, hypertension, and diabetes in shift workers (3, 5, 6)....
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TL;DR: The concept of sleep health synergizes with other health care agendas, such as empowering individuals and communities, improving population health, and reducing health care costs, and offers the field of sleep medicine new research and clinical opportunities.
Abstract: Good sleep is essential to good health. Yet for most of its history, sleep medicine has focused on the definition, identification, and treatment of sleep problems. Sleep health is a term that is infrequently used and even less frequently defined. It is time for us to change this. Indeed, pressures in the research, clinical, and regulatory environments require that we do so. The health of populations is increasingly defined by positive attributes such as wellness, performance, and adaptation, and not merely by the absence of disease. Sleep health can be defined in such terms. Empirical data demonstrate several dimensions of sleep that are related to health outcomes, and that can be measured with self-report and objective methods. One suggested definition of sleep health and a description of self-report items for measuring it are provided as examples. The concept of sleep health synergizes with other health care agendas, such as empowering individuals and communities, improving population health, and reducing health care costs. Promoting sleep health also offers the field of sleep medicine new research and clinical opportunities. In this sense, defining sleep health is vital not only to the health of populations and individuals, but also to the health of sleep medicine itself.
1,222 citations
TL;DR: The relationship between the circadian and metabolic systems and the implications for cardiovascular disease, obesity, and diabetes are reviewed.
855 citations
Cites background from "Is there an association between shi..."
...Cross-sectional studies have uncovered an increased prevalence of metabolic syndrome, high body mass index (BMI), and cardiovascular events in shift workers (Ellingsen et al., 2007; Karlsson et al., 2001)....
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TL;DR: In humans, prolonged sleep restriction with concurrent circadian disruption alters metabolism and could increase the risk of obesity and diabetes, and a cautionary message for employers to guard against causing adverse metabolic effects in workers by their shift scheduling practices is carried.
Abstract: Epidemiological studies link short sleep duration and circadian disruption with higher risk of metabolic syndrome and diabetes. We tested the hypotheses that prolonged sleep restriction with concurrent circadian disruption, as can occur in people performing shift work, impairs glucose regulation and metabolism. Healthy adults spent >5 weeks under controlled laboratory conditions in which they experienced an initial baseline segment of optimal sleep, 3 weeks of sleep restriction (5.6 hours of sleep per 24 hours) combined with circadian disruption (recurring 28-hour "days"), followed by 9 days of recovery sleep with circadian re-entrainment. Exposure to prolonged sleep restriction with concurrent circadian disruption, with measurements taken at the same circadian phase, decreased the participants' resting metabolic rate and increased plasma glucose concentrations after a meal, an effect resulting from inadequate pancreatic insulin secretion. These parameters normalized during the 9 days of recovery sleep and stable circadian re-entrainment. Thus, in humans, prolonged sleep restriction with concurrent circadian disruption alters metabolism and could increase the risk of obesity and diabetes.
794 citations
TL;DR: These findings highlight an integrative role of circadian rhythms in physiology and offer a new perspective for treating chronic diseases in which metabolic disruption is a hallmark.
Abstract: A majority of mammalian genes exhibit daily fluctuations in expression levels, making circadian expression rhythms the largest known regulatory network in normal physiology. Cell-autonomous circadian clocks interact with daily light-dark and feeding-fasting cycles to generate approximately 24-hour oscillations in the function of thousands of genes. Circadian expression of secreted molecules and signaling components transmits timing information between cells and tissues. Such intra- and intercellular daily rhythms optimize physiology both by managing energy use and by temporally segregating incompatible processes. Experimental animal models and epidemiological data indicate that chronic circadian rhythm disruption increases the risk of metabolic diseases. Conversely, time-restricted feeding, which imposes daily cycles of feeding and fasting without caloric reduction, sustains robust diurnal rhythms and can alleviate metabolic diseases. These findings highlight an integrative role of circadian rhythms in physiology and offer a new perspective for treating chronic diseases in which metabolic disruption is a hallmark.
636 citations
References
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TL;DR: In summary, insulin resistance appears to be a syndrome that is associated with a clustering of metabolic disorders, including non-insulin-dependent diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerotic cardiovascular disease.
Abstract: Diabetes mellitus is commonly associated with systolic/diastolic hypertension, and a wealth of epidemiological data suggest that this association is independent of age and obesity. Much evidence indicates that the link between diabetes and essential hypertension is hyperinsulinemia. Thus, when hypertensive patients, whether obese or of normal body weight, are compared with age- and weight-matched normotensive control subjects, a heightened plasma insulin response to a glucose challenge is consistently found. A state of cellular resistance to insulin action subtends the observed hyperinsulinism. With the insulin/glucose-clamp technique, in combination with tracer glucose infusion and indirect calorimetry, it has been demonstrated that the insulin resistance of essential hypertension is located in peripheral tissues (muscle), is limited to nonoxidative pathways of glucose disposal (glycogen synthesis), and correlates directly with the severity of hypertension. The reasons for the association of insulin resistance and essential hypertension can be sought in at least four general types of mechanisms: Na+ retention, sympathetic nervous system overactivity, disturbed membrane ion transport, and proliferation of vascular smooth muscle cells. Physiological maneuvers, such as calorie restriction (in the overweight patient) and regular physical exercise, can improve tissue sensitivity to insulin; evidence indicates that these maneuvers can also lower blood pressure in both normotensive and hypertensive individuals. Insulin resistance and hyperinsulinemia are also associated with an atherogenic plasma lipid profile. Elevated plasma insulin concentrations enhance very-low-density lipoprotein (VLDL) synthesis, leading to hypertriglyceridemia. Progressive elimination of lipid and apolipoproteins from the VLDL particle leads to an increased formation of intermediate-density and low-density lipoproteins, both of which are atherogenic. Last, insulin, independent of its effects on blood pressure and plasma lipids, is known to be atherogenic. The hormone enhances cholesterol transport into arteriolar smooth muscle cells and increases endogenous lipid synthesis by these cells. Insulin also stimulates the proliferation of arteriolar smooth muscle cells, augments collagen synthesis in the vascular wall, increases the formation of and decreases the regression of lipid plaques, and stimulates the production of various growth factors. In summary, insulin resistance appears to be a syndrome that is associated with a clustering of metabolic disorders, including non-insulin-dependent diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerotic cardiovascular disease.
4,582 citations
"Is there an association between shi..." refers background in this paper
...The findings on disturbances in glucose and serum lipids raises the question whether shift work could induce insulin resistance—a lowered sensitivity in muscle, liver and fat cells to the actions of insulin—which is the underlying cause for the metabolic syndrome. The disturbances comprising the metabolic syndrome are obesity (especially abdominal fat accumulation), dyslipidaemia with high triglycerides and low high density lipoprotein (HDL) cholesterol concentrations, hypertension, and a low fibrinolytic activity....
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TL;DR: Sleep debt has a harmful impact on carbohydrate metabolism and endocrine function similar to those seen in normal ageing and, therefore, sleep debt may increase the severity of age-related chronic disorders.
3,322 citations
"Is there an association between shi..." refers background in this paper
...showed that the postprandial glucose concentrations were higher after a meal when the circadian rhythm was phase shifted. A more complex diurnal metabolic regulation has also been suggested involving the pattern of sleep debt, indicating that the quality and duration of sleep could impact on metabolic and endocrine function....
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TL;DR: The literature on shift work, morbidity and mortality from cardiovascular disease, and changes in traditional risk factors is reviewed and shift workers were found to have a 40% increase in risk.
Abstract: The literature on shift work, morbidity and mortality from cardiovascular disease, and changes in traditional risk factors is reviewed. Seventeen studies have dealt with shift work and cardiovascular disease risk. On balance, shift workers were found to have a 40% increase in risk. Causal mechanisms of this risk via known cardiovascular risk factors, in relation to circadian rhythms, disturbed sociotemporal patterns, social support, stress, behavior (smoking, diet, alcohol, exercise), and biochemical changes (cholesterol, triglycerides, etc) are discussed. The risk is probably multifactorial, but the literature has focused on the behavior of shift workers and has neglected other possible causal connections. In most studies methodological problems are present; these problems are related to selection bias, exposure classification, outcome classification, and the appropriateness of comparison groups. Suggestions for the direction of future research on this topic are proposed.
648 citations
TL;DR: Data from this prospective cohort of US female nurses are compatible with the possibility that 6 or more years of shift work may increase the risk of CHD in women.
Abstract: Background The purpose of this study was to examine prospectively the relation of shift work to risk of coronary heart disease (CHD) in a cohort of women. Methods and Results An ongoing prospective cohort of US female nurses, in whom we assessed (in 1988) the total number of years during which they worked rotating night shifts (at least three nights per month in addition to day and evening shifts), included 79 109 women, 42 to 67 years old in 1988, who were free of diagnosed CHD and stroke. Incident CHD was defined as nonfatal myocardial infarction and fatal CHD. During 4 years of follow-up (1988 to 1992), 292 cases of incident CHD (248 nonfatal myocardial infarction and 44 fatal CHD) occurred. The age-adjusted relative risk of CHD was 1.38 (95% CI, 1.08 to 1.76) in women who reported ever doing shift work compared with those who had never done so. The excess risk persisted after adjustment for cigarette smoking and a variety of other cardiovascular risk factors. Compared with women who had never done shift work, the multivariate adjusted relative risks of CHD were 1.21 (95% CI, 0.92 to 1.59) among women reporting less than 6 years and 1.51 (95% CI, 1.12 to 2.03) among those reporting 6 or more years of rotating night shifts. Conclusions These data are compatible with the possibility that 6 or more years of shift work may increase the risk of CHD in women.
496 citations
TL;DR: This initial observation of release of eosinophil chemotactic factor of anaphylaxis in vivo along with histamine assigns the mast cell a central role in cold urticaria.
Abstract: Patients with idiopathic acquired cold-induced urticaria were evaluated for the release of the preformed mast-cell mediators of immediate-type hypersensitivity during a study in which one ...
384 citations