Reduction of rapid eye movement (REM) sleep by glucose alone or glucose and insulin in rats

How does diurnal intermittent fasting impact sleep, daytime sleepiness, and markers of the biological clock? Current insights

Mealtimes and feeding schedules may interfere with the circadian system and impact sleep. The practice of intermittent fasting (IF) in its different formats is increasing worldwide. However, most studies addressing the effect of IF on circadian rhythms, daytime sleepiness, and sleep architecture have been conducted during diurnal IF for Ramadan. In this article, we analyze the effect of diurnal IF on the circadian clock, sleep, and daytime sleepiness. In free-living, unconstrained environments that do not control for lifestyle changes such as sleep/wake schedules, sleep duration, and light exposure, studies have demonstrated sudden and significant delays in bedtime and wake time during diurnal intermittent fasting for Ramadan. However, subsequent studies that accounted for lifestyle factors and sleep/wake patterns have reported no changes in markers of the biological clock, daytime sleepiness, or sleep parameters. Nevertheless, several researchers have demonstrated a reduction in the proportion of rapid eye movement stage sleep as the significant alteration in sleep architecture during fasting.

The effect of intermittent fasting during Ramadan on sleep, sleepiness, cognitive function, and circadian rhythm

PURPOSE

Studies have shown that experimental fasting can affect cognitive function, sleep, and wakefulness patterns. However, the effects of experimental fasting cannot be generalized to fasting during Ramadan due to its unique characteristics. Therefore, there has been increased interest in studying the effects of fasting during Ramadan on sleep patterns, daytime sleepiness, cognitive function, sleep architecture, and circadian rhythm.

METHOD

In this review, we critically discuss the current research findings in those areas during the month of Ramadan.

RESULTS

Available data that controlled for sleep/wake schedule, sleep duration, light exposure, and energy expenditure do not support the notion that Ramadan intermittent fasting increases daytime sleepiness and alters cognitive function. Additionally, recent well-designed studies showed no effect of fasting on circadian rhythms. However, in non-constrained environments that do not control for lifestyle changes, studies have demonstrated sudden and significant delays in bedtime and wake time.

CONCLUSIONS

Studies that controlled for environmental factors and sleep/wake schedule reported no significant disturbances in sleep architecture. Nevertheless, several studies have consistently reported that the main change in sleep architecture during fasting is a reduction in the proportion of REM sleep.

Long-Term Single and Joint Effects of Excessive Daytime Napping on the HOMA-IR Index and Glycosylated Hemoglobin: A Prospective Cohort Study

This prospective cohort study was conducted to assess the duration of daytime napping and its effect combined with night sleep deprivation on the risk of developing high HOMA-IR (homeostasis model assessment of insulin resistance) index and disadvantageous changes in glycosylated hemoglobin (HbA1c) levels.A total of 5845 diabetes-free subjects (2736 women and 3109 men), 30 to 65 years of age, were targeted for this cohort study since 2008. Multiple adjusted Cox regression models were performed to evaluate the single and joint effects of daytime napping on the risk of an elevated HbA1c level and high HOMA-IR index.After an average of 4.5 years of follow-up, >30 minutes of daytime napping was significantly associated with an increased risk of an elevated HbA1c level (>6.5%) in men and women (all P trend < 0.05). Hazard ratios (HRs) for an HbA1c level between 5.7% and 6.4% were also significant in the entire cohort and women, but nonsignificant in men. HRs (95% confidence interval, CIs) for the high HOMA-IR index in the entire cohort, men, and women were 1.33 (1.10-1.62), 1.46 (1.08-1.98), and 1.47 (1.12-1.91), respectively. The combination of sleep deprivation with no naps or >30 minutes napping and the combination of no sleep deprivation with >30 minutes daytime napping were all associated with an HbA1c level >6.5% (HR = 2.08, 95% CI = 1.24-3.51; HR = 4.00, 95% CI = 2.03-7.90; and HR = 2.05, 95% CI = 1.29-3.27, respectively). No sleep deprivation combined with >30 minutes daytime napping correlated with a high risk of an HbA1c level between 5.7% and 6.4% and high HOMA-IR index (HR = 2.12, 95% CI = 1.48-3.02; and HR = 1.35, 95% CI = 1.10-1.65, respectively).Daytime napping >30 minutes was associated with a high risk of an elevated HbA1c level and high HOMA-IR index. No sleep deprivation combined with napping >30 minutes carries a risk of abnormal glucose metabolism. Sleep deprivation combined with brief daytime napping <30 minutes was not associated with a risk for an elevated HbA1c level and high HOMA-IR index.

Insulinoma Masquerading as Rapid Eye Movement Sleep Behavior Disorder: Case Series and Literature Review

Insulinoma is a rare endocrine tumor that can cause a wide variety of symptoms, including abnormal nocturnal behavior. We report on 3 patients with insulinoma who presented with abnormal nocturnal behavior and injury during sleep, which simulated rapid eye movement (REM) sleep behavior disorder (RBD). In case 1, the fasting glucose level was 15  mg/dL, and insulin levels were elevated (15  μU/mL). In case 3, when the patient was transferred to the hospital because of a disturbance of consciousness, hypoglycemia (29  mg/dL) was detected. In contrast, in case 2, fasting glucose sampling did not indicate hypoglycemia, but continuous glucose monitoring revealed nocturnal hypoglycemia. The time from initial symptoms to a diagnosis of insulinoma ranged from 7 months to 2 years. All 3 patients had previously received anticonvulsant drugs for suspected epilepsy, but the medications were ineffective. Polysomnography showed no evidence of REM sleep without atonia in any of the 3 patients. No patient remembered any events that occurred during sleep. When a patient manifests abnormal behavior during the night and early morning, glucose monitoring should be performed, especially during the night and early morning. Clinicians should be aware that although insulinomas are rare, they can mimic parasomnias, such as RBD.

Non-random temporal distribution of sleep onset REM periods in the MSLT in narcolepsy

STUDY OBJECTIVES

The diagnosis of narcolepsy is supported by the presence of two or more sleep onset REM periods (SOREMPs) in the multiple latency sleep test (MSLT). The distribution of SOREMPs throughout the MSLT has not been systematically studied in narcolepsy. We studied the temporal distribution of SOREMPs in the MSLT of a large series of narcoleptics and calculated the effects of age and the diagnostic value of shorter versions of the test.

PATIENTS

129 patients consecutively diagnosed with narcolepsy (73.4% with cataplexy) underwent nocturnal polysomnography followed by a five-nap MSLT.

RESULTS

429 SOREMPs were recorded in 645 MSLT naps (66.5%). The probability of presenting SOREMPs in the fourth nap (3:30 pm) was significantly lower than in the remaining naps: 22.4% SOREMPs in the first nap, 20.5% in the second, 20.5% in the third, 16% in the fourth and 20.5% in the fifth nap (p<0.034). Patients older than 29 years had less SOREMPs than the younger ones (p:0.045). Shortening the MSLT to three or four naps decreased the capability of the test to support the diagnosis of narcolepsy in 14.7 and 10% respectively.

CONCLUSION

The temporal distribution of SOREMPs in the MSLT is not even in narcolepsy, with the fourth nap having the lowest probability of presenting a SOREMP. This should be taken into account when evaluating the results of the MSLT, and particularly when using shorter versions of the test.

Intermittent fasting during Ramadan: does it affect sleep?

Islamic intermittent fasting is distinct from regular voluntary or experimental fasting. We hypothesised that if a regimen of a fixed sleep-wake schedule and a fixed caloric intake is followed during intermittent fasting, the effects of fasting on sleep architecture and daytime sleepiness will be minimal. Therefore, we designed this study to objectively assess the effects of Islamic intermittent fasting on sleep architecture and daytime sleepiness. Eight healthy volunteers reported to the Sleep Disorders Centre on five occasions for polysomnography and multiple sleep latency tests: (1) during adaptation; (2) 3 weeks before Ramadan, after having performed Islamic fasting for 1 week (baseline fasting); (3) 1 week before Ramadan (non-fasting baseline); (4) 2 weeks into Ramadan (Ramadan); and (5) 2 weeks after Ramadan (non-fasting; Recovery). Daytime sleepiness was assessed using the Epworth Sleepiness Scale and the multiple sleep latency test. The participants had a mean age of 26.6 ± 4.9 years, a body mass index of 23.7 ± 3.5 kg m(-2) and an Epworth Sleepiness Scale score of 7.3 ± 2.7. There was no change in weight or the Epworth Sleepiness Scale in the four study periods. The rapid eye movement sleep percentage was significantly lower during fasting. There was no difference in sleep latency, non-rapid eye movement sleep percentage, arousal index and sleep efficiency. The multiple sleep latency test analysis revealed no difference in the sleep latency between the 'non-fasting baseline', 'baseline fasting', 'Ramadan' and 'Recovery' time points. Under conditions of a fixed sleep-wake schedule and a fixed caloric intake, Islamic intermittent fasting results in decreased rapid eye movement sleep with no impact on other sleep stages, the arousal index or daytime sleepiness.

Decreasing concentration of interstitial glucose in REM sleep in subjects with normal glucose tolerance

AIMS

Sleep is divided into two major stages, non-rapid eye movement (NREM) and rapid eye movement (REM), which are distinct in various neuroendocrine respects. NREM/REM cycles influence insulin and glucagon secretion; however, glucose concentrations in REM compared with NREM have not been directly explored. The aim was to investigate the differences in glucose concentrations in interstitial fluid (IGC) between NREM/REM cycles using a continuous glucose monitoring system (CGMS).

METHODS

Thirteen subjects were eligible for analysis out of the 28 enrolled. All underwent standard polysomnography for the assessment of sleep stages and the exclusion of sleep apnoea syndrome with CGMS and subsequent morning oral glucose tolerance test (exclusion of glucose intolerance or diabetes).

RESULTS

The IGC in REM fell in 12 out of the 13 subjects, whereas the IGC in NREM increased in eight out of the 13 subjects. Therefore, the mean change of IGC differed in direction between sleep stages: -0.028 (-0.045 to -0.011) for REM vs. 0.005 (-0.012 to 0.017) for NREM [median (QR), P = 0.007, n = 13], with the mean difference of 0.038 mmol/l x 5 min(-1) (95% confidence interval 0.012, 0.064). The mean glucose concentration in REM sleep was lower than in NREM: 4.29 +/- 1.00 vs. 4.53 +/- 0.90 mmol/l (mean +/- sd, P = 0.003, n = 13).

CONCLUSIONS

The decrease in IGC in REM compared with NREM sleep, with lower absolute values, may arise from different physiological events observed in these sleep stages. The REM-related decline in glucose concentrations may be a risk factor for nighttime hypoglycaemia.

Does Ramadan fasting affect sleep?

Experimental fasting has been shown to alter the sleep-wakefulness pattern in various species. As fasting during Ramadan is distinct from experimental fasting, the physiological and behavioural changes occurring during Ramadan fasting may differ from those occurring during experimental fasting. There has been increased interest in recent years in sleep changes and daytime sleepiness during Ramadan. Moreover, many of those who fast during Ramadan associate this fasting with increased daytime sleepiness and decreased performance. This raises the question of whether Ramadan fasting affects sleep. In this review, we discuss the findings of research conducted to assess changes in sleep pattern, chronobiology, circadian rhythms, daytime sleepiness and function and sleep architecture during the month of Ramadan. Where applicable, these findings are compared with those obtained during experimental fasting.

Active immunization of rats against insulin beta subunits: effects on sleep and feeding

The effects of active immunization against peripheral insulin beta subunits on different sleep variables and food consumption were studied in rats. Insulin subunits beta coupled to thyroglobulin was used as immunogen and rats immunized with thyroglobulin alone served as controls. Active immunization against insulin beta subunits affects sleep variables, particularly slow-wave sleep during the dark period, increasing significantly this stage of sleep and decreasing waking. Feeding behavior and body weight remained unchanged. These results are compatible with previous studies showing a positive correlation between decrease of insulin secretion and sleep disturbances. A possible relationship between peripheral alpha and or beta subunits of insulin, sleep, and feeding is suggested.

Active immunization against insulin affects sleep and feeding in rats

The effects of active immunization against peripheral insulin on different sleep parameters and food consumption were studied in rats. Insulin coupled to thyroglobulin was used as immunogen and rats immunized with thyroglobulin alone served as controls. Active immunization against insulin is summarized as follows: (a) the number of arousals was reduced; (b) waking time decreased by about 20%; (c) slow wave sleep was increased; (d) The amount of sleep increased during the light and dark period; (e) feeding was decreased; (f) body weight was reduced; and (g) the blood glucose level rised. These results are compatible with previous studies showing positive correlation between decrease of insulin secretion, sleep disturbances and decrease of feeding. A possible association between peripheral insulin and brain noradrenergic system, sleep and feeding is suggested.