Shift Work and Metabolic Syndrome: Respective Impacts of Job Strain, Physical Activity, and Dietary Rhythms

Abstract

The impact of shift work on cardiovascular disease (CVD) risk factors and metabolic syndrome are not yet completely understood. The objectives of this study were to evaluate the impact of shift work on metabolic syndrome according to two different definitions in a population of strictly rotating shift workers (3x8 h) compared to paired counterparts working only day hours, and to study whether shift work itself is a determinant of metabolic syndrome after taking into account a large panel of confusing factors. We conducted a cross-sectional study comparing 98 strictly rotating shift workers to 100 regular day-workers (all subjects had a long experience of their working rhythms) within the same petrochemical plant. Clinical, behavioral, occupational, and biological data were collected, and a detailed nutritional investigation was done. Shift and day workers were comparable in terms of major CVD factors, and both had a 10 yr Framingham risk scoring of 11%. Shift workers reported an increased job strain and higher total and at-work physical activity. Alterations in metabolic parameters were evident with a rise in triglycerides, free fatty acids, and gamma glutamyl transpeptidase and lower HDL-cholesterol. Multiple logistic regression analysis demonstrated that shift work was associated with occurrence of metabolic syndrome, as defined by the National Cholesterol Education Program-ATPIII criteria, OR: 2.38 (1.13-4.98), but not using the more recent score from the International Diabetes Federation, which gives a major emphasis on abdominal obesity. Total energy intake and contributions of the major nutrients did not differ between the two groups, with the notable exception of saturated lipids (+10% in shift workers). Meal distribution was clearly different: energy intake was more fractionated within the day, with a lesser contribution of breakfast and lunch but with increased intakes during intermediate light meals, particularly in the afternoon and night. Multivariate analyses were performed to test for the influence of dietary rhythms on the development of an NCEP-ATPIII metabolic syndrome. Dietary intakes at breakfast and during intermediate light meals appear to be "protective" against metabolic syndrome, while a high load at dinner favors its occurrence. A high intake at lunch is particularly deleterious to shift workers. However, in all tested models, shift work remained significantly associated with metabolic syndrome, after taking into account potential covariates like job strain, physical activity, quantitative dietary parameters, and meal distribution. A specific follow-up of shift workers should be recommended to occupational physicians.

Adverse metabolic and mental health outcomes associated with shiftwork in a population-based study of 277,168 workers in UK biobank

“…Interestingly however, previous studies consistently report little or no difference between the dietary intake of shiftworkers and non-shiftworkers [1,9,25,26] although the frequency and timing of meals is very potently disturbed, [26] and the risk of shiftworkers having metabolic syndrome was associated with the timing of meals but not with overall energy intake. [25] Human circadian rhythms in glucose and insulin sensitivity are optimised towards ingestion of food in daytime, yet shiftwork often necessitates that food is ingested at night when these endogenous metabolic rhythms are not prepared for food. Experimental studies in humans and animals have shown that this metabolic mismatch can disrupt blood glucose and triglyceride rhythmicity, [27] dampen liver transcriptional rhythms, [28] and ultimately lead to compromised pancreatic beta cell function, decreased energy expenditure, leptin resistance, and diabetes.…”

“…Shiftworkers were more likely to have higher BMI despite higher physical activity, yet there is little evidence that they eat more than non-shiftworkers. [4,25] It may be more beneficial to modulate the timing and frequency of their meals and activity rather than volume. However, even if this were possible, it will not address the fundamental uncoupling of physiological and environmental timing that most likely underlies the effects of shiftwork on metabolism and behaviour.…”

Pharmacological modulators of the circadian clock as potential therapeutic drugs

“…The mutation results in a single amino acid change in CK1ε binding domain of the hPER2 molecule, which affects the level of its phosphorylation and stability [55]. More recently, a number of epidemiological studies have suggested that people who work in rotating shifts or at night show a higher incidence of carcinogenesis, heart disease, and metabolic syndrome caused by circadian desynchronization [56][57][58]. These people also have higher rates of errors and accidents and often experience a significant loss of alertness and ability to make decisions.…”

Les récepteurs REVERBα et REVERBβ donnent letempo

“…Or, nous montrons que CLOCK, seul ou avec BMAL1, est capable d'activer la transcription de Lpl [6]. Cette dérégulation de la Lpl, qui favoriserait l'utilisation des acides gras dans le muscle et l'adipogenèse dans le tissu adipeux blanc, aurait pour origine la surexpression de CLOCK en l'absence de REVERB (Figure 1 [1,2]. Le simple fait de nourrir des souris avec la même quantité de nourriture pendant la phase de repos au lieu de les nourrir pendant la phase active conduit à une augmentation de prise de poids [3].…”