Relationship of chronotype and social jetlag with adherence to the Japanese dietary guidelines among workers

Association of Social Jetlag with the Dietary Quality Among Korean Workers: Findings from a Nationwide Survey

Background/Objectives: Social jetlag, which refers to the misalignment between biological rhythms and social schedule, is linked to an increased risk of metabolic diseases. This cross-sectional study investigated the relationship between social jetlag and workers' dietary quality. Methods: This secondary data analysis included a sample of workers from the Korea National Health and Nutrition Examination Survey (n = 11,430). Social jetlag was determined by calculating the difference in the sleep midpoint between free days and workdays, based on sleep onset and offset times. The Korean Health Eating Index (KHEI) was calculated based on 24-h recalls, with higher scores indicating superior dietary qualities (range: 0-100). Poor dietary quality was defined as a KHEI below the lowest quartile (<51.6). Linear or logistic regressions were utilized to estimate β or odds ratio (OR), respectively. Results: Among study participants, 12.1% of workers experienced ≥120 min of social jetlag. ≥120 min of social jetlag was associated with a reduced KHEI score compared with 0-59 min (β: -1.23, 95% confidence interval [CI]: -2.16, -0.30). Those with ≥120 min of social jetlag were more likely to have poor dietary quality than those with 0-59 min (OR: 1.27, 95% CI: 1.08, 1.50). Conclusions: Workers experiencing ≥120 min of social jetlag had poorer dietary quality compared with workers with 0-59 min of social jetlag. Therefore, this study suggests that policy efforts are needed to reduce social jetlag among workers in Korea.

Is the association between social jetlag and BMI mediated by lifestyle? A cross-sectional survey study in the Dutch general population

OBJECTIVE

Social jetlag is a discordance between the social and biological rhythm and is associated with higher HbA1c, higher BMI, and higher odds of obesity. The pathways that could explain these associations are still debated. This study aims to assess the mediating role of several lifestyle factors in the cross-sectional association between social jetlag and BMI.

METHODS

We used cross-sectional data from 1784 adults from urban areas in the Netherlands, collected in 2019. Social jetlag (difference in midpoint of sleep between week and weekend nights) was categorized as low(<1 h), moderate(1-2h), and high(>2 h). BMI(kg/m2) was calculated from self-reported height and weight. The association between social jetlag and BMI was assessed using linear regression, adjusted for sex, age, education, and sleep duration and stratified for the effect modifier stress (high vs. low). Mediation analysis was performed for self-reported smoking, physical activity, alcohol consumption, and adherence to a healthy diet.

RESULTS

High social jetlag was associated with higher BMI (0.69 kg/m2,95%CI 0.05;1.33). This association was stronger in people with high stress (0.93 kg/m2,95%CI 0.09;1.76). Social jetlag was also associated with higher odds of smoking, lower physical activity, higher alcohol consumption, and lower healthy diet adherence. In people with high stress, these factors mediated 10-15% of the association between social jetlag and BMI.

CONCLUSIONS

Social jetlag is associated with higher BMI and this association is stronger in people with high stress. In people with high stress, healthy diet adherence mediated 12% of this association. Other pathways involved in this association should be further investigated.

The Recommendation of the Mediterranean-styled Japanese Diet for Healthy Longevity

The Mediterranean diet, listed as the intangible cultural heritage of humanity by UNESCO, is known as healthy and consumed worldwide. The Japanese diet is also listed and considered healthy. This narrative review compares the Mediterranean diet with its Japanese counterpart. Research has reported that people in Mediterranean regions, such as Italy and Greece, have one-third of the mortality ratio from cardiovascular diseases compared to people in the United States and Northern Europe because of the difference in eating habits. Therefore, Mediterranean diets are considered as healthy. A typical Western diet containing high amounts of fat, sugar, and calories is responsible for several diseases like metabolic syndrome and obesity, which are induced by chronic inflammation. In contrast, Mediterranean and Japanese diets contain them only less. The similarity between Mediterranean and Japanese diets is the substantial intake of vegetables, beans, and fish. On the other hand, the Mediterranean diet consumes large amounts of olive oil, especially polyphenol-rich extra virgin olive oil and dairy products, but meat consumption is relatively small. In contrast, the Japanese diet does not use oil and fat, contains abundant fermented foods, and consumes seaweed. Japan is known for its longevity, and people think that a well-balanced diet daily is good for preventing and curing illness. In this regard, finding non-disease conditions, so-called "ME-BYO," and curing them before the manifestation of diseases is becoming more common. In this review, we discuss the healthy eating habit, "The Mediterranean-styled Japanese diet," which prevents ME-BYO condition and reduces the risk of various diseases. The Mediterranean-styled Japanese diet, a hybrid of Mediterranean and Japanese diets, reduces the risk of various diseases by suppressing chronic inflammation. This nutritional intervention prevents ME-BYO and is beneficial for healthy longevity. Hence, a Mediterranean-styled Japanese diet might be helpful for healthy longevity in Japan and around the world.

Chronotype is associated with addiction-like eating behavior, mindful eating and ultra-processed food intake among undergraduate students

This study aimed to investigate the relationships between chronotype and addiction-like eating behavior, mindful eating and ultra-processed food consumption among undergraduate students. Specific and validated scales were used in order to evaluate chronotype, addiction-like eating behavior and mindful eating (N = 605). Dietary intake was determined by food frequency questionnaire and percentage energy from ultra-processed food was calculated. Self-reported weights and heights were obtained from the participants. Mean scores of scales, social jetlag, energy intake, ultra-processed food intake and BMI were compared by chronotypes. Associations between chronotype, addiction-like eating behavior, mindful eating, ultra-processed food consumption and BMI were determined by Pearson's test. The relationships between chronotype and addiction-like eating behavior, mindful eating and ultra-processed food intake were assessed by linear regression models and adjusted for sex, BMI, energy intake, season, smoking and alcohol consumption. Evening-type participants had higher scores of social jetlag (2.01 ± 0.09), appetitive drive (26.02 ± 0.63), low dietary control (20.50 ± 0.41), addiction-like eating behavior (46.52 ± 0.85), lower scores of recognition (21.91 ± 0.43) and higher percentage energy from ultra-processed food (32.24 ± 1.26%). Chronotype score showed negative associations with addiction like eating behavior (β=-0.247, p < 0.001) and ultra-processed food consumption (β=-0.247, p < 0.001), and a positive association with recognition (β = 0.124, p < 0.001). Results suggest that chronotype is inversely associated with addiction-like eating behavior and ultra-processed food consumption, and positively associated with mindful eating among undergraduate students.

Irregular sleep and cardiometabolic risk: Clinical evidence and mechanisms

Sleep regularity is an essential part of the multidimensional sleep health framework. The phenomenon of irregular sleep patterns is widespread in contemporary lifestyles. This review synthesizes clinical evidence to summarize the measures of sleep regularity and discusses the role of different sleep regularity indicators in developing cardiometabolic diseases (coronary heart disease, hypertension, obesity, and diabetes). Existing literature has proposed several measurements to assess sleep regularity, mainly including the standard deviation (SD) of sleep duration and timing, sleep regularity index (SRI), interdaily stability (IS), and social jetlag (SJL). Evidence on associations between sleep variability and cardiometabolic diseases varies depending on the measure used to characterize variability in sleep. Current studies have identified a robust association between SRI and cardiometabolic diseases. In comparison, the association between other metrics of sleep regularity and cardiometabolic diseases was mixed. Meanwhile, the associations of sleep variability with cardiometabolic diseases differ across the population. SD of sleep characteristics or IS may be more consistently associated with HbA1c in patients with diabetes compared with the general population. The association between SJL and hypertension for patients with diabetes was more accordant than in the general population. Interestingly, the age-stratified association between SJL and metabolic factors was observed in the present studies. Furthermore, the relevant literature was reviewed to generalize the potential mechanisms through which irregular sleep increases cardiometabolic risk, including circadian dysfunction, inflammation, autonomic dysfunction, hypothalamic-pituitary-adrenal (HPA) axis disorder, and gut dysbiosis. Health-related practitioners should give more attention to the role of sleep regularity on human cardiometabolic in the future.