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Circadian rhythms, regulated by internal biological clocks, are the natural oscillations of physical, mental, and behavioral processes that follow a 24-hour cycle.¹ Sleeping is an example of a circadian pattern where the daily light and dark cycle acts as an important natural physiological cue. Further, chronotype reflects an individual’s circadian rhythm and describes at what time of day a person is more naturally inclined to sleep and to be awake, ranging from early types to late types (i.e., “early birds” and “night-owls”) and those in between.

Disruptions to circadian rhythms have been associated with negative health impacts, from neurodegenerative risks to mood disorders to cardiometabolic dysfunctions.^2-6 In addition, research suggests that metabolic health may be negatively impacted when sleeping patterns diverge from an individual’s circadian chronotype.⁷ Recent reporting now indicates that circadian misalignment may also impact gut health and function.^8,9

Social Jetlag, Circadian Cycles, and the Gut Microbiome

Circadian misalignment has previously been associated with lifestyle patterns such as later meal timing, chronic shift work, and social jetlag.^10-12 Social jetlag is a term used to describe a conflict between a person’s circadian rhythm and the rhythm of their social life, or their school, work, and family schedules. For example, sleep and wake times may be adjusted on workdays and then shifted to alternate times on work-free days. Social jetlag is reportedly more prevalent in individuals with late chronotypes who have naturally later sleep and wake times.⁹

Animal-model research and clinical studies have suggested that disruption of the circadian sleep-wake cycle may not only lead to overall circadian dysregulation but also to gut microbiota dysbiosis.^8,13 A recent human-based study has continued this line of research and investigated the impact of circadian misalignment from social jetlag and habitual sleep disruption on gut microbiome health.⁹

The 2023 Bermingham investigation included participants from the ZOE PREDICT 1 cohort study (n=1,002 twin and non-twin adults with mean age of 46 years; 90% white; 72% female; mean BMI of 25.6).⁹ Health data from 934 of the participants was included in the final analysis. Self-reported habitual sleep was used to calculate social jetlag and chronotype. Social jetlag was indicated when the difference between midpoint of sleep on week and weekend days was greater than or equal to 1.5 hours. Cross-sectional statistical analysis reported the following results:⁹

• Social jetlag: 16% of the 934 included individuals were affected by social jetlag. Participants with social jetlag were more likely to be male (39% vs 25%), shorter sleepers (less than seven hours), be a late chronotype with delayed timing for first daily meals, and younger (mean age of 38.4 years) compared to the no social jetlag group. The study did not include information on shift work or employment status.
• Diet/inflammation: Those participants with social jetlag were more often associated with an overall reduced intake of plant-based diets, higher intake of potatoes and sugar-sweetened beverages, lower intake of fruits and nuts, and higher markers of inflammation compared to no social jetlag participants. This reflects the results of other studies that have indicated that those with social jetlag are associated with less favorable dietary patterns,¹⁴ including an increased consumption of sugar-sweetened beverages, total fat, and saturated fat, and with indicators of metabolic dysfunction including obesity and higher BMI, waist circumference, and systolic blood pressure.^7,15
• Sleep amount: Overall, 82% of participants reported getting an average amount of sleep (seven to nine hours per night), regardless of social jetlag status.
• Gut microbiome: Researchers did not conclude that the overall microbiome composition was predictive of social jetlag; however, single bacterial species were found to be differentially abundant between the groups. Nine species were at least 20% prevalent and in greater abundance in those with social jetlag compared to those with no social jetlag, and several of the species have been previously identified as unfavorable (or potentially unfavorable) to gut health, such as Phocaeicola vulgatus, Blautia obeum, Enterocloster bolteae, Ruminococcus gnavus, and Flavonifractor plautii. Of interesting note, researchers indicated that diet quality in part appeared to mediate the link between social jetlag and some unfavorable microbiota species, highlighting the potential positive impact of modifiable dietary factors on gut microbiota dysbiosis due to circadian disruptions.

Investigators concluded that a small degree of circadian misalignment is associated with diet and non-diet-mediated gut dysbiosis, even among those who get the recommended amounts of sleep.⁹

The mechanisms that explain the circadian interactions between the gut microbiome and related metabolites, clock genes, and internal biological clocks continue to be investigated.^16,17 However, research has already demonstrated that the gastrointestinal system has cyclic variations during the day and that healthy gut-related circadian rhythms are modulated in large part by food intake and meal timing.¹⁸

The influence of circadian rhythms on health across body systems is evident, and recognizing and addressing circadian misalignment due to lifestyle factors may help to further personalize and optimize healthcare interventions. Treatments based on circadian rhythms have been seen in light therapy for seasonal depression, meal timing for optimal glucose and insulin responsiveness, and medication timing for blood pressure management. Researchers have also taken a closer look at maximizing the benefits of exercise by considering diurnal timing.

Helping patients live in line with their chronotype by exercising, sleeping, or eating at optimal times and on optimal schedules may be an important consideration for the most effective and sustainable health treatment strategy. To read more about chronotherapeutics, please see the related IFM-authored articles below.

Related Articles

Chronobiology: A Dynamic Field of Rhythm and Clock Genes

Chrononutrition: Food Timing, Circadian Fasting, and the Body’s Internal Clock

Circadian Fasting & Precursors to Heart Health

 References

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3. Rana S, Prabhu SD, Young ME. Chronobiological influence over cardiovascular function: the good, the bad and the ugly. Circ Res. 2020;126(2):258-279. doi:1161/CIRCRESAHA.119.313349
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9. Bermingham KM, Stensrud S, Asnicar F, et al. Exploring the relationship between social jetlag with gut microbial composition, diet and cardiometabolic health, in the ZOE PREDICT 1 cohort. Eur J Nutr. Published online August 2, 2023. doi:1007/s00394-023-03204-x
10.  Adafer R, Messaadi W, Meddahi M, et al. Food timing, circadian rhythm and chrononutrition: a systematic review of time-restricted eating’s effects on human health. Nutrients. 2020;12(12):3770. doi:3390/nu12123770
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15.  Bouman EJ, Beulens JWJ, Groeneveld L, et al. The association between social jetlag and parameters of metabolic syndrome and type 2 diabetes: a systematic review and meta-analysis. J Sleep Res. 2023;32(3):e13770. doi:1111/jsr.13770
16.  Zhang Y, Li Y, Barber AF, et al. The microbiome stabilizes circadian rhythms in the gut. Proc Natl Acad Sci U S A. 2023;120(5):e2217532120. doi:1073/pnas.2217532120
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18.  Codoñer-Franch P, Gombert M, Martínez-Raga J, Cenit MC. Circadian disruption and mental health: the chronotherapeutic potential of microbiome-based and dietary strategies. Int J Mol Sci. 2023;24(8):7579. doi:3390/ijms24087579