An exploratory pilot study on social rhythm regularity, and its associations with sleep, circadian, affective, and alcohol use outcomes in late adolescents.

The current exploratory pilot study examined whether social rhythm regularity, as measured by a social rhythm metric, was associated with: (1) the regularity of circadian rhythms and/or sleep regularity metrics; and (2) sleep quality, affective function and alcohol use. Late adolescents (18-22 years old) who drink alcohol (n = 36; 61.1% female, Mage = 21.26 years) completed a 14-day ecological momentary assessment protocol, wore a wrist actigraph for 14 days, and completed two overnight visits (Thursday and Sunday) to assess dim light melatonin onset. Sleep regularity metrics included standard deviation, composite phase deviation, social jet lag and inter-daily stability. We used dim light melatonin onset data to calculate the stability of the circadian phase (Sunday minus Thursday). Participants completed surveys and ecological momentary assessments that assessed global and daily sleep quality, affective function, and alcohol use. Correlational analysis and robust regression modelling were used. More regular social rhythms were associated with higher regularities of mid-sleep timing based on standard deviations, but were not associated with other sleep regularity metrics or stability of the circadian phase. More regular social rhythms were associated with better sleep quality, but were not associated with affective function or alcohol use. Social rhythm regularity is a unique construct compared with existing sleep quality metrics. In contrast with the social zeitgeber hypothesis, social rhythm regularity was not associated with circadian rhythm regularity measured by dim light melatonin onset. However, social rhythm regularity may be an under-recognized contributor to better sleep quality.

Association between sleep regularity and arterial stiffness among middle-age adults in Southwestern China.

BACKGROUND: Sleep regularity has been linked to a risk of arterial stiffness (AS). However, the association between sleep regularity indicators, which reflect 24-hour sleep variability, and AS has not yet been examined. METHODS: We analyzed data from 516 adults, aged 40-65 years (the median age of 51 years), from the 'Follow-up Study of Sleep Characteristics and Chronic Diseases in the Middle-aged and Elderly Population in Guizhou Province'. Participants underwent assessments of AS (OMRON HBP-8000, baPWV ≥ 1400 cm/s) and sleep (wrist smart band (Honor band 5i) for ≥ 7 days). Logistic regression was utilized to evaluate the odds ratio (OR) and 95% confidence interval (CI) of the association between sleep regularity and AS. RESULTS: A total of 516 people were included in this study, of which 279 (54.07%) were in the AS group. The univariate results showed that the AS group (Median 71.18) had lower SRI compared to the No-AS group (Median 75.00) (p < 0.001). The multifactorial results showed participants with higher SRI scores were more likely to have a lower risk of AS compared to those with lower SRI scores (ORQ4 VS. Q1=0.46, 95%CI: 0.25-0.85, p = 0.013). The SRI effect was more pronounced in male (ORQ4 VS. Q1=0.28, 95%CI: 0.12-0.69, p = 0.005), snoring populations (ORQ4 VS. Q1=0.13, 95%CI: 0.04-0.48, p = 0.002), and non-retired populations (ORQ4 VS. Q1=0.45, 95%CI: 0.22-0.92, p = 0.028). CONCLUSIONS: The present findings indicated that the effect between SRI and AS may be more sensitive than the standard deviation of sleep duration as well as the standard deviation of sleep onset.

Ethnic/racial discrimination and academic grades among adolescents: moderation by sleep regularity.

This study investigates how sleep regularity moderates the association between ethnic/racial discrimination and academic grades among diverse adolescents. The study included a 14-day, daily diary and actigraphy study of ninth-grade adolescents in the United States (N = 265; mean [SD] age 15.26 [0.62] years, 41.51% Asian, 21.13% Black, 37.35% Latinx, 71.32% female) who completed measures of demographic information and ethnic/racial discrimination (Daily Life Experiences Racism and Bother subscale). Sleep data were collected for 14 consecutive days with wrist actigraphy, and sleep regularity was calculated using the Sleep Regularity Index (SRI). Academic grades were provided by the Department of Education. Discrimination frequency was associated with lower academic grades, and the SRI moderated this association. Compared to adolescents who had moderate and regular SRI profiles, adolescents with irregular SRI (i.e., lower sleep regularity) had stronger negative associations between discrimination and grades. On the other hand, for adolescents who had moderate to high sleep regularity, there was no significant association between discrimination and grades. This study underscores the importance of sleep regularity for adolescents' academic achievement.

Greater sleep variability is associated with higher systemic inflammation in type 2 diabetes.

Sleep irregularity and variability have been shown to be detrimental to cardiometabolic health. The present pilot study explored if higher day-to-day sleep irregularity and variability were associated with systemic inflammation, as assessed by high-sensitivity C-reactive protein, in type 2 diabetes. Thirty-five patients with type 2 diabetes (mean age 54.3 years, 54.3% female) who were not shift-workers participated. The presence of diabetic retinopathy was determined. The standard deviation of sleep duration and sleep midpoint across all recorded nights were used to quantify sleep variability and regularity, respectively, assessed by 14-day actigraphy. The presence and severity of sleep apnea were assessed using an overnight home monitor. Low-density lipoprotein, haemoglobin A1C and high-sensitivity C-reactive protein were collected. Multiple regression analysis using natural-log-transformed values was performed to establish an independent association between sleep variability and high-sensitivity C-reactive protein. Twenty-two (62.9%) patients had diabetic retinopathy. The median (interquartile range) of high-sensitivity C-reactive protein was 2.4 (1.4, 4.6) mg L-1 . Higher sleep variability was significantly associated with higher high-sensitivity C-reactive protein (r = 0.342, p = 0.044), as was haemoglobin A1C (r = 0.431, p = 0.010) and low-density lipoprotein (r = 0.379, p = 0.025), but not sleep regularity, sleep apnea severity or diabetic retinopathy. Multiple regression analysis showed that higher sleep variability (B = 0.907, p = 0.038) and higher HbA1c (B = 1.519, p = 0.035), but not low-density lipoprotein, contributed to higher high-sensitivity C-reactive protein. In conclusion, higher sleep variability in patients with type 2 diabetes who were not shift-workers was independently associated with higher systemic inflammation, conferring increased cardiovascular risk. Whether sleep interventions to reduce sleep variability can reduce systemic inflammation and improve cardiometabolic health should be investigated.

Sleep regularity in healthy adolescents: Associations with sleep duration, sleep quality, and mental health.

Current evidence points to the importance of sleep for adolescent physical and mental health. To date, most studies have examined the association between sleep duration/quality and health in adolescence. An emerging line of research suggests that regularity in the timing of sleep may also play an important role in well-being. To address this aspect of sleep, the present study investigated daily variability of sleep, quantified using the sleep regularity index (SRI), in 46 adolescents (M = 12.78 ± 1.07 years) and its association with depressive symptoms/mental health. Sleep was measured during a 6 month period (M = 133.11 ± 36.42 nights) using actigraphs to quantify SRI values calculated for school days, weekends and holidays. Depressive symptoms and general psychopathology were assessed at the beginning (baseline) and end (follow-up) of the actigraphy measurements. Sleep was most regular during school days and associated with a longer total sleep time, shorter sleep onset latency, and higher sleep efficiency. Moreover, a higher SRI on school days was associated with fewer depressive symptoms at follow-up, whereas higher SRI on weekends was associated with less overall psychopathology at follow-up. Furthermore, the change in overall psychopathology, but not depressive symptoms across the two assessments was correlated with sleep regularity index. Our results suggest that regular timing of sleep is associated with sleep that is of longer duration and higher quality and may be protective of adolescent mental health. Therefore, adolescents should be encouraged not only to get enough sleep, but also to retain regular sleeping patterns to promote well-being and mental health.

Sleep Regularity and Cardiometabolic Heath: Is Variability in Sleep Patterns a Risk Factor for Excess Adiposity and Glycemic Dysregulation?

PURPOSE OF REVIEW: Night-to-night variability in sleep patterns leads to circadian disruption and, consequently, could increase cardiometabolic risk. The purpose of this review is to summarize findings from studies published between 2015 and 2020 examining various measures of night-to-night variability in sleep in relation to metabolic syndrome (MetS), type 2 diabetes (T2D), and their risk factors. We illustrate a potential causal pathway between irregular sleep patterns and T2D, highlighting knowledge gaps along the way. RECENT FINDINGS: Across different measures of sleep variability, irregular sleep patterns were associated with poorer cardiometabolic outcomes. Higher standard deviations (SD) across nights of sleep duration and onset or midpoint of sleep were associated with increased odds of having MetS and clusters of metabolic abnormalities as well as greater adiposity and poorer glycemic control. Conversely, greater regularity of rest-activity patterns related to lower risk for T2D. Social jetlag was associated with glycemic dysregulation, adiposity, T2D, and MetS. These associations are often observed in both metabolically healthy and unhealthy individuals; both higher SD of sleep duration and social jetlag relate to poorer glucose regulation in individuals with diabetes. There is consistent evidence of associations of sleep variability with increased risk for adiposity, glucose dysregulation, T2D, and MetS. Although experimental evidence is needed to determine causation, there is support to recommend stabilizing sleep patterns for cardiometabolic risk prevention.

Dietary Intake and Eating-Related Cognitions Related to Sleep Among Adolescents Who Are Overweight or Obese.

OBJECTIVE : To examine associations of sleep duration and regularity with dietary intake and eating-related cognitions among adolescents who are overweight/obese. METHODS : Participants were 315 adolescents being evaluated through Healthy Kids, Healthy Weight. Outcomes were reported sleep duration and regularity (bedtime shift, wake-time shift, sleep duration shift). Major predictors were dietary intake (e.g., consumption of calories and sugar-sweetened beverages) and eating-related cognitions (food preoccupation, eating self-efficacy). RESULTS : Findings were that staying up (i.e., bedtime shift) and sleeping in later (i.e., wake-time shift) on weekends compared with weekdays significantly relates to drinking more sugar-sweetened beverages, the latter for males. Sleeping in on weekends was related to greater food preoccupation. CONCLUSIONS : Sleep regularity was the most important variable in its relationships with dietary intake. Evaluating sleep patterns and improving them with behavioral interventions should be considered as an additional weight loss strategy to promote dietary adherence.

Late evening electric light exposure is associated with low sleep regularity in adolescents living in rural areas.

In this study, we tested the prediction that sleep regularity would be lower in adolescents exposed to late evening electric light (LEEL) than in those without exposure to it. The Sleep Regularity Index was calculated based on actigraph recordings from adolescents living in rural communities in Argentina and Brazil that were either exposed to LEEL or not. The effect of the LEEL on sleep variables was tested using linear models considering sex and age, as well as accounting for the differences between countries. Sleep onset was delayed, sleep duration shortened, and Sleep Regularity Index was 4 [1-8] points lower in the group exposed to LEEL (p = .0176, eta2 =0.13). Our results show that beyond sleep phase and duration, which are known to be affected by LEEL in this age group, sleep irregularity should also be considered as an important outcome variable when assessing the adverse effects of evening light on adolescents.

Later circadian timing and increased sleep timing variability are associated with attenuations in overnight blood pressure dipping among chronic nightshift workers.

OBJECTIVE: Determine relationships between overnight blood pressure, circadian phase, and sleep variability among dayshift and chronic nightshift nurses. METHODS: Twenty participants working dayshift (n = 10) or nightshift (n = 10) schedules participated in a 7-day cross-sectional study. Participants underwent an evening in-laboratory melatonin assessment and wore ambulatory blood pressure devices to assess 24-hour blood pressure patterns. Overnight blood pressure dipping was calculated from sleeping/waking systolic blood pressure ratio and salivary dim-light melatonin onset determined circadian phase. Sleep variability was assessed using the standard deviation of 7-day sleep onset. RESULTS: Nightshift workers had later circadian phase, greater sleep onset variability, and an attenuated overnight blood pressure dipping pattern. Later circadian phase was associated with attenuated dipping patterns and sleep onset variability was negatively correlated with blood pressure dipping magnitude in nightshift, but not dayshift workers. CONCLUSIONS: Chronic circadian disruption via higher sleep onset variability among nightshift workers may contribute to attenuated blood pressure dipping and cardiovascular risk in this population.

The Emerging Importance of Sleep Regularity on Cardiovascular Health and Cognitive Impairment in Older Adults: A Review of the Literature.

The regularity of sleep/wake patterns across multiple days is emerging as an important determinant of health. However, the association between sleep regularity and health outcomes in the aging population is not well understood. The current systematic review identified 22 publications that examined the relationship between sleep regularity and selected health outcomes: cardiovascular risk, cognitive impairment, and mortality. All studies were published after 2010, reflecting a growing research interest in daily sleep regularity. Low sleep regularity was consistently associated with higher cardiovascular risk and elevated risk of all-cause mortality. Results on cognitive impairment are mixed, with inconsistency likely attributed to small sample sizes and differences in sleep regularity assessment. Overall, regularity in sleep carries important information about health and should be included in future studies that collect daily sleep measures. Gaps in literature and methodological shortcomings are discussed.