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.

Study objective Environmental-factor changes may largely be accountable for the dramatic increase of obesity prevalence in industrialized countries. This study ...

Many of the health problems that are more prevalent among shiftworkers are thought to be linked to their heightened susceptibility to metabolic syndrome, i.e., the association of even moderate degrees of visceral obesity, dyslipidemia, abnormal blood pressure, and serum glucose levels in the same individual. Although previous studies have identified associations between shiftwork and metabolic syndrome, there is relatively little evidence to date of how the risk of developing it varies as a function of exposure to shiftwork. The current study seeks to confirm earlier findings of an association between shiftwork exposure and metabolic dysfunction, and to examine the impact of exposure duration, while adjusting for a number of covariates in the analyses. The analyses were based on data from VISAT, a study involving the measurement of physiological, behavioral, and subjective outcomes from 1757 participants, 989 being current or former shiftworkers. The sample comprised employed and retired wage earners, male and female, who were 32, 42, 52, and 62 yrs old. The first analysis sought to confirm previous findings of an association between exposure to shiftwork and the risk of developing metabolic syndrome. It indicated that participants who were or who had previously been shiftworkers (i.e., working schedules that involved rotating shifts; not being able to go to bed before midnight; having to get up before 05:00 h; or being prevented from sleeping during the night) were more likely to exhibit symptoms of metabolic syndrome, after adjusting for age, sex, socioeconomic status, smoking, alcohol intake, perceived stress, and sleep difficulty (odds ratio [OR] 1.78; 95% confidence interval [CI] 1.03–3.08). The results suggest the association between shiftwork and metabolic syndrome cannot be fully accounted for by either higher levels of strain or increased sleep difficulty among shiftworkers, although it remains a possibility that either one or both of these factors may have played a contributing role. The second analysis addressed the issue of duration of exposure to shiftwork. Participants with >10 yrs' experience of working rotating shifts were more likely to exhibit symptoms of metabolic syndrome than participants without exposure to shiftwork, i.e., dayworkers, even after adjusting for age and sex (OR 1.96; 95% CI 1.03–3.75). Thus, the current study confirms the association between shiftwork exposure and metabolic syndrome. It also provides new information regarding the time course of the development of the illness as function of exposure duration, although this was only examined in relation to rotating shiftwork. It is concluded that those responsible for monitoring workers' health should pay particular attention to indices of metabolic dysfunction in workers who have been exposed to shiftwork for >10 yrs. (Author correspondence: p. t. tucker@swansea. ac. uk )

Objective: To evaluate the existing evidence on the effect of night-shift work and its subtypes (permanent and rotating) on cardiovascular risk factors: diabetes, lipid disorders, being overweight, hypertension, smoking habits, sedentariness, and occupational psychosocial stressors.Method: A Web of Sciences and Cochrane review library search was conducted to identify systematic reviews with or without meta-analysis dealing with the quantification of the link between night-shift work and the studied cardiovascular risk factors in working populations. We used the AMSTAR 2 to evaluate the quality of each review. The main results of the included systematic reviews were compiled in a summary structured around the different cardiovascular risk factors.Results: After selection, 33 systematic reviews were included: nine for diabetes, four for lipid disorders, nine for being overweight, four for hypertension, two for smoking habits, three for occupational psychosocial stressors and two for sedentariness. The results confirmed an excess risk of diabetes of about 10% regardless of the type of night work. A stated excess risk of being overweight at around 25% was also highlighted for shift workers overall, which could reach 38% among night-shift workers. An increased risk of obesity, estimated at 5% for night-shift workers and at 18% for rotating shift workers, was observed. An excess risk of hypertension was estimated at around 30% when considering the broad definition of shift work and when night periods were included in rotating shifts. The literature provided inconsistent results for the link between lipid disorders and night-shift work. Shift workers appeared to be more likely to smoke. The link between shift work and occupational psychosocial stressors was scarcely explored in the available studies. Sedentariness was scarcely considered in systematic reviews, which prevents any firm conclusions.Conclusion: The consequences of night work in terms of diabetes, being overweight/obesity and hypertension are established. Monitoring of these cardiovascular risk factors for these night-shift workers could be implemented by practitioners. In contrast, the links with lipid disorders, sedentariness, smoking habits, and occupational psychosocial stressors warrant further investigation.Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021275212, PROSPERO (ID CRD42021275212)

<!--field: Resume--> Cet article présente les objectifs et la méthodologie de l’étude prospective VISAT (Vieillissement, Santé, Travail). L’étude a été conçue pour préciser dans quelle mesure et comment la nature des tâches, l’organisation du travail, l’exposition à des nuisances et autres conditions d’exercice de l’activité influencent la disponibilité des ressources physiologiques et psychologiques des individus, en lien avec les effets du vieillissement sur ces mêmes ressources. Par rapport à des études antérieures sur le sujet, l’accent a été mis davantage sur les composantes psychologiques, à la fois des contraintes de travail et des ressources individuelles. Plusieurs options stratégiques structurent l’étude VISAT: (i) le partenariat entre chercheurs et médecins du travail (ii) la centration sur une population de salariés actifs et non actifs (iii) le choix d’un suivi longitudinal sur dix ans avec trois mesures (iv) l’adoption d’une conception large de la santé, et (v) la prise en compte des ressources cognitives. Quelques exemples d’objectifs spécifiques de recherche sont présentés avec leur ancrage théorique. Sur le plan méthodologique, cette recherche repose sur des données recueillies par questionnaire et par des mesures cliniques effectuées par des médecins du travail à l’occasion de la visite médicale annuelle du travail auprès d’un échantillon tiré au sort de 3 237 salariés ou anciens salariés de tous secteurs économiques, nés en 1964, 1954, 1944, et 1934. Lors du premier recueil, en 1996, ceux nés en 1934 étaient en majorité des retraités. Une 2^e vague de recueil de données est en cours en 2001, et une 3^e est prévue cinq ans plus tard. Le matériel permet le recueil d’informations sur la vie professionnelle actuelle et passée, d’informations et de mesures médicales effectuées par le médecin et d’informations sur la vie hors travail. L’étape longitudinale doit permettre de dissocier différents phénomènes indexés au temps et de lever ainsi certaines difficultés d’interprétation liées à la méthode transversale. <!--field: -->