Social jetlag, obesity and metabolic disorder: investigation in a cohort study

Abstract

BACKGROUND Obesity is one of the leading causes of preventable death worldwide. Circadian rhythms are known to control both sleep timing and energy homeostasis, and disruptions in circadian rhythms have been linked with metabolic dysfunction and obesity-associated disease. In previous research, social jetlag, a measure of chronic circadian disruption caused by the discrepancy between our internal versus social clocks, was associated with elevated self-reported body mass index, possibly indicative of a more generalized association with obesity and metabolic dysfunction. METHODS We studied participants from the population-representative Dunedin Longitudinal Study (N = 1037) to determine whether social jetlag was associated with clinically assessed measurements of metabolic phenotypes and disease indicators for obesity-related disease, specifically, indicators of inflammation and diabetes. RESULTS Our analysis was restricted to N = 815 non-shift workers in our cohort. Among these participants, we found that social jetlag was associated with numerous clinically assessed measures of metabolic dysfunction and obesity. We distinguished between obese individuals who were metabolically healthy versus unhealthy, and found higher social jetlag levels in metabolically unhealthy obese individuals. Among metabolically unhealthy obese individuals, social jetlag was additionally associated with elevated glycated hemoglobin and an indicator of inflammation. CONCLUSIONS The findings are consistent with the possibility that ‘living against our internal clock’ may contribute to metabolic dysfunction and its consequences. Further research aimed at understanding that the physiology and social features of social jetlag may inform obesity prevention and have ramifications for policies and practices that contribute to increased social jetlag, such as work schedules and daylight savings time.

Social jetlag in health and behavioral research: a systematic review

“…data on height and weight in one study 21 versus assessment of BMI variables by staff members in another, 22 or to different sample characteristics, since Roenneberg et al 21 studied individuals primarily from central Europe with a broader age range, while Johnsen et al 22 investigated a population located at higher latitudes, above the Arctic Circle. Corroborating the hypothesis of the influence of latitude, Parsons et al 23 found an association between SJL and higher BMI, fat mass and probability of being obese (BMI ≥30 kg/m 2 ) in individuals from midlatitudes, while Polugrudov et al 24 found no association of SJL with BMI and waist circumference in a population living in the subarctic. Furthermore, none of these studies controlled the results for energy intake, energy expenditure or body fat.…”

“…Kantermann et al 25 found no association between SJL and metabolic risk parameters in male shift workers, which may be due to the small sample size. However, Parsons et al 23 found that individuals with higher SJL were more likely to meet the criteria for metabolic syndrome and Wong et al 26 found higher cardiometabolic risk markers associated with higher SJL in larger samples of both sexes. Regarding the risk of cardiovascular pathologies, a positive correlation between SJL and heart rate has been demonstrated.…”

Meal irregularity and cardiometabolic consequences: results from observational and intervention studies

“…A less extreme form of living against our internal body clock, but which affects far more people, is caused by the so-called social jetlag (30) . Social jetlag is the discrepancy between our internal body clocks and our social clock and this has also been associated with increased risk for non-communicable chronic diseases such as obesity (30) and the metabolic syndrome (7) . It has been estimated that social jetlag affects more than 80 % of the general population in central Europe (30) , especially people living in urban areas.…”

“…It has been hypothesised that consuming irregular or inconsistent meals affects our internal body clock, also called chrono-biological or circadian rhythms, and could thereby have an impact on metabolic disease risk. Circadian rhythms are biological rhythms that follow a 24 h cycle, from Latin meaning 'approximate day' (7) . It is known that many physiologically and nutritionally relevant processes in the human body have circadian rhythms, including glycolysis and gluconeogenesis, cholesterol and lipid metabolism, oxidative phosphorylation and detoxification pathways (8,9) .…”

Consequences of circadian dysregulation on metabolism

“…Additionally, social jet lag was also associated with indicators of inflammation and diabetes in "metabolically unhealthy" obese participants. 91 Delaying bedtime by 8.5 hours for 4 days decreases insulin sensitivity and inflammation. 92 Endocrine rhythms, specifically leptin and melatonin, are depressed in night active individuals, defined as having an average sleep onset of 01:30 hours relative to 22:30 hours in control participants.…”