Sleep deprivation

A study involving 1426 long-term survivors of childhood cancer (survivors of eight different childhood cancers who were treated between 1970 and 1986) has revealed cognitive impairment in over a fifth. Those who reported problems sleeping or frequent daytime sleepiness and fatigue were three to four times more likely to have attention and memory problems.

Additionally, those who were taking antidepressants were 50% more likely to report attention problems and 70% more likely to report memory problems.

From the Whitehall II study, data involving 5431 older participants (45-69 at baseline) has revealed a significant effect of midlife sleep changes on later cognitive function. Sleep duration was assessed at one point between 1997 and 1999, and again between 2002 and 2004. A decrease in average night’s sleep from 6, 7, or 8 hours was significantly associated with poorer scores on tests of reasoning, vocabulary, and the MMSE. An increase from 7 or 8 hours (but not from 6 hours) was associated with lower scores on these, as well as on tests of phonemic and semantic fluency.

In a study involving 44 young adults given a rigorous memorizing task at noon and another such task at 6pm, those who took a 90-minute nap during the interval improved their ability to learn on the later task, while those who stayed awake found it harder to learn.

Comparison of 17 people with severe obstructive sleep apnea (OSA) with 15 age-matched controls has revealed that those with OSA had reduced gray matter in several brain regions, most particularly in the left parahippocampal gyrus and the left posterior parietal cortex, as well as the entorhinal cortex and the right superior frontal gyrus. These areas were associated with deficits in abstract reasoning and executive function. Deficits in the left posterior parietal cortex were also associated with daytime sleepiness.

A study involving 48 healthy adults aged 18-39 has found that extraverts who were deprived of sleep for 22 hours after spending 12 hours in group activities performed worse on a vigilance task that did those extraverts who engaged in the same activities on their own in a private room. Introverts were relatively unaffected by the degree of prior social interaction.

A study involving 135 adults (33-65) has found that, not only did patients with obstructive sleep apnea who were being treated with CPAP therapy outperform untreated OSA patients on an overnight picture memory task, but they outperformed controls who did not have OSA. The memory task involved being shown 20 photographs before spending the night in the sleep lab, and then having to choose the familiar photo from 20 similar pairs in the morning. CPAP therapy provides a steady stream of air through a mask that is worn during sleep.

A study involving 163 overweight children and adolescents aged 10 to 17 has revealed that moderate to severe obstructive sleep apnea was linked to both lower academic grades and behavioral concerns. None of the students with moderate to severe OSA had an "A" average, and 30% had a "C" average or lower. In contrast, roughly 15% of those without sleep-disordered breathing had an "A" average, and only about 15% had a "C" average or lower. The results remained significant after adjustment for sex, race, socioeconomic status and sleep duration on school nights.

A national study involving some 8,000 children, has revealed receptive and expressive language, phonological awareness, literacy and early math abilities were all better in 4-year-old children whose parents reported having rules about what time their child goes to bed. Having an earlier bedtime also was predictive of higher scores for most developmental measures. Recommendations are that preschool children get a minimum of 11 hours of sleep each night.

It’s not just a matter of quantity; quality of sleep matters too. A study involving 72 adults (average age 40), whose sleep was monitored for 11 consecutive nights, has revealed that reaction times on a morning psychomotor vigilance task was significantly slower after exposure to recorded traffic noise during sleep. The slowing was directly related to the frequency and sound-pressure level of the nightly noise.