Sleep restriction progress to cardiac autonomic imbalance

The association between sleep duration and muscle sympathetic nerve activity

PURPOSE

Sleep duration is associated with risk of hypertension and cardiovascular diseases. It is thought that shorter sleep increases sympathetic activity. However, most studies are based on acute experimental sleep deprivation that have produced conflicting results. Furthermore, there are limited data available on habitual sleep duration and gold-standard measures of sympathetic activation. Hence, this study aimed to assess the association between habitual sleep duration and muscle sympathetic nerve activity.

METHODS

Twenty-four participants aged ≥ 18 years were included in the study. Sleep was assessed using at-home 7-day/night actigraphy (ActiGraph™ GT3X-BT) and sleep questionnaires (Pittsburgh Sleep Quality Index and Epworth Sleepiness Scale). Microelectrode recordings of muscle sympathetic nerve activity were obtained from the common peroneal nerve. Participants were categorised into shorter or longer sleep duration groups using a median split of self-report and actigraphy sleep measures.

RESULTS

Compared to longer sleepers, shorter sleepers averaged 99 ± 40 min and 82 ± 40 min less sleep per night as assessed by self-report and objective measures, respectively. There were no differences in age (38 ± 18 vs 39 ± 21 years), sex (5 male, 7 female vs 6 male, 6 female), or body mass index (23 ± 3 vs 22 ± 3 kg/m2) between shorter and longer sleepers. Expressed as burst frequency, muscle sympathetic nerve activity was higher in shorter versus longer sleepers for both self-report (39.4 ± 12.9 vs 28.4 ± 8.5 bursts/min, p = 0.019) and objective (37.9 ± 12.4 vs 28.1 ± 8.8 bursts/min, p = 0.036) sleep duration.

CONCLUSIONS

Shorter sleep duration assessed in a home setting was associated with higher muscle sympathetic nerve activity. Sympathetic overactivity may underlie the association between short sleep and hypertension.

Effects of Sleep Deprivation on the Tryptophan Metabolism

Sleep has a regulatory role in maintaining metabolic homeostasis and cellular functions. Inadequate sleep time and sleep disorders have become more prevalent in the modern lifestyle. Fragmentation of sleep pattern alters critical intracellular second messengers and neurotransmitters which have key functions in brain development and behavioral functions. Tryptophan metabolism has also been found to get altered in SD and it is linked to various neurodegenerative diseases. The kynurenine pathway is a major regulator of the immune response. Adequate sleep alleviates neuroinflammation and facilitates the cellular clearance of metabolic toxins produced within the brain, while sleep deprivation activates the enzymatic degradation of tryptophan via the kynurenine pathway, which results in an increased accumulation of neurotoxic metabolites. SD causes increased production and accumulation of kynurenic acid in various regions of the brain. Higher levels of kynurenic acid have been found to trigger apoptosis, leads to cognitive decline, and inhibit neurogenesis. This review aims to link the impact of sleep deprivation on tryptophan metabolism and associated complication in the brain.

Smokeless tobacco: Risk factor for cardiovascular and breathing in young Indian adolescent

BACKGROUND

Teenagers are the foremost susceptible population to smokeless tobacco usage and limited studies have surveyed the influence of smokeless tobacco on cardiac and respiratory response.

OBJECTIVE

This study aims to measure consequence (cardiovascular and breathing) of smokeless tobacco usage (gutkha and chewing tobacco) among young Indian men.

METHOD

On random basis, the applicants were divided into Group I (n=50) - healthy control group, Group II (n=50) - smokeless tobacco users. Anthropometric measurements and recording of blood pressure (BP), pulse wave analysis (PWV), heart rate variability (HRV) and pulmonary function test (PFT) was performed.

RESULT

We observed that altogether anthropometric variables were comparable among all individuals. In blood pressure variable, except DBP, other variables for example SBP, PP and MAP were significantly increased in Group II individuals, once compare to Group I. Pulse wave analysis, (such as, AP, AIx, and SEVR), was comparable in individuals of both groups. As compare to Group I, HR was significantly increased in Group II. In HRV investigation, NN, VLF, LF, LF(nu), LF/HF were increased significantly and TSP, HF, HF(nu) were decreased significantly in Group II with compare to Group I. In PFT analysis, FVC was comparable among individuals of both the group and conversely, significant decrease in FEV₁, FEV₁/FVC, FEF_25-75 and PEFR in Group II when compare with Group I.

CONCLUSION

This study illustrate that smokeless tobacco practice has increasing adverse effects on cardiovascular as well as breathing system and become an important public health problem.