Effect of aging on cardiac and electroencephalographic arousal in sleep apnea/hypopnea syndrome

Effects of long sleep time and irregular sleep-wake rhythm on cognitive function in older people

Sleep disturbances and cognitive decline are common in older adults. We aimed to investigate the effects of the total sleep time (TST) and sleep–wake rhythm on executive function and working memory in older adults. In 63 older participants, we measured the TST, wake after sleep onset (WASO), and sleep timing (midpoint between bedtime and wake-up time) using actigraphy. Executive function was evaluated with the trail making test B (TMT-B) and Wisconsin card sorting test (WCST). The number of back task (N-back task) was used to measure working memory. Participants with a TST ≥ 8 h had a significantly lower percentage of correct answers (% correct) on the 1-back task than those with a TST < 8 h. The % correct on the 1-back task was significantly correlated with the TST, WASO, and sleep timing. Multiple regression analyses revealed that the TST and sleep timing were significant factors of the % correct on the 1-back task. The TMT-B score was significantly correlated with the sleep timing. Category achievement on the WCST was significantly correlated with the standard deviation of the sleep timing. Therefore, a long sleep time and an irregular sleep–wake rhythm could have adverse effects on executive function and working memory in older people.

Poor sleep quality impairs cognitive performance in older adults

The prevalence of insomnia increases with age. Short sleep duration is associated with deficits in cognitive performance. We hypothesized that short sleep duration and sleep quality influence cognitive performance in older adults. The study included 78 adults aged 60 years and over (72.2 ± 5.9 years). Total sleep time and sleep efficiency (total sleep time/time in bed × 100) were calculated using actigraphy. We evaluated cognitive performance with the continuous performance test-identical pairs and the number-back test. Sleep apnea was evaluated overnight with a portable home monitoring system. The accuracy of the 0-back test significantly decreased in participants with total sleep time less than 5 h compared with those with total sleep time greater than 7 h, but there was no significant difference in continuous performance test-identical pairs between the two groups. Participants with sleep efficiency <85% showed a significant decrease in 0- and 1-back test accuracy compared with those with sleep efficiency ≥85%. There were no significant differences in the accuracy of number-back tests and continuous performance test-identical pairs between apnea-hypopnea index ≥15 h(-1) and apnea-hypopnea index <15 h(-1) groups, or among lowest SpO2  ≥ 90%, lowest 80-90%, and lowest SpO2  < 80% groups. Age, total sleep time and sleep efficiency were significantly correlated with accuracy on the 0-back test. Age and sleep efficiency were significantly correlated with accuracy on the 1-back test. Multiple regression analysis revealed that total sleep time was independently correlated with accuracy on the 0-back test, while age was independently correlated with accuracy on the 1-back test. Our findings suggest that sleep duration and sleep quality may play a role in cognitive performance in older adults.

Can O2 dysregulation induce premature aging?

Chronic intermittent or episodic hypoxia, as occurs during a number of disease states, can have devastating effects, and prolonged exposure to this hypoxia can result in cell injury or cell death. Indeed, intermittent hypoxia activates a number of signaling pathways that are involved in oxygen sensing, oxidative stress, metabolism, catecholamine biosynthesis, and immune responsiveness. The cumulative effect of these processes over time can undermine cell integrity and lead to a decline in function. Furthermore, the ability to respond adequately to various stressors is hampered, and this is traditionally defined as premature aging or senescence. This review highlights recent advances in our understanding of the cellular and molecular mechanisms that are involved in the response to intermittent hypoxia and the potential interplay among various pathways that may accelerate the aging process.

Blood pressure and heart rate during continuous experimental sleep fragmentation in healthy adults

STUDY OBJECTIVES

This paper aims to determine whether experimental arousals from sleep delay the sleep related fall in cardiovascular activity in healthy adults.

DESIGN

We report the results of 2 studies. The first experiment manipulated arousals from sleep in young adults. The second compared the effect of frequent arousals on young and middle-aged adults. The influence of arousals were assessed in 2 ways; (1) the fall in cardiovascular activity over sleep onset and the early sleep period, and (2) the underlying sleep levels during the sleep periods in between arousals.

SETTING

Both experiments were conducted in the sleep laboratory of the Department of Psychology, The University of Melbourne, Australia.

PARTICIPANTS

There were 5 male and 5 female healthy individuals in each experiment between the ages of 18-25 years (Experiment 1) and 38-55 years (Experiment 2).

INTERVENTIONS

Participants in Experiment 1 were aroused by auditory stimuli every (i) 2 min, (ii) 1 min, and (iii) 30 sec of sleep for 90 min after the first indication of sleep. In a control condition, participants slept undisturbed for one NREM sleep cycle. Experiment 2 compared the control with the 30-sec condition in the young adults and in an additional group of middle-aged adults.

MEASUREMENTS AND RESULTS

The dependent variables were blood pressure (BP) and heart rate (HR). In Experiment 1, sleep fragmentation at higher frequencies retarded the fall in BP over sleep onset but did not affect the underlying sleep levels. Experiment 2 showed that there were no age differences on the effect of arousals on changes in BP and HR during sleep.

CONCLUSIONS

This paper supports the hypothesis that repetitive arousals from sleep independently contribute to elevations in BP at night.

The progressive effects of ageing on chemosensitivity in healthy subjects

The aim of this study was to compare the central inspiratory drive (P(0.1)) response to hypoxia and hypercapnia between different age groups of elderly, nonsmoker, healthy subjects and young healthy controls. A random sample, proportionally stratified by age (65-69, 70-74, 75-79 and 80-84 yrs) from a sample of nonsmoker elderly subjects representative of a general population and 47 healthy subjects aged 20-40 were selected. Arterial blood gas, lung volumes, diffusing capacity, maximal respiratory pressure and oxygen uptake measurements were performed. Breathing pattern and mouth occlusion pressure, as well as P(0.1) responses to hyperoxic progressive hypercapnia and isocapnic progressive hypoxia were evaluated. The elderly subjects had lower P0.1 responses to hypoxia (0.017+/-0.006 vs. 0.031+/-0.008 kPa/%, P<0.001) and hypercapnia (0.042+/-0.018 vs. 0.051+/-0.030 kPa/mmHg, P=0.047) than the young healthy controls. Hypoxic sensitivity gradually decreased as age increased to 70-74 and remained unchanged from 75 years of age onward. CO(2) threshold was lower in the elderly groups than in young healthy controls. Lung volumes, inspiratory muscle strength and baseline metabolic rate were the principal determinants of hypoxic sensitivity. In summary, during old age, a progressive decline in hypoxic sensitivity and a decrease in the CO(2) threshold are experienced. These alterations remain stable from the age of 75 onward.

Daytime sleepiness and automobile accidents in patients with obstructive sleep apnea syndrome

We evaluated the rate of automobile accidents and daytime sleepiness using the Epworth sleepiness scale (ESS) in 44 patients with obstructive sleep apnea syndrome (OSAS). We defined the automobile accident score as a sum of two points for every one automobile accident and one point for every near-miss accident. Automobile accidents and near-misses were found in 54.5% and 50.0% in patients with OSAS. Automobile accident score was significantly correlated with the ESS score (r=0.56, P < 0.01). Our findings suggest that ESS score may be useful in detecting patients with the potential risk of automobile accidents associated with daytime sleepiness.