Data from international studies demonstrate that "synchronised" start times for adolescents are far later than the start times in the overwhelming majority of educational institutions. In 1997, University of Minnesota research compared students who started school at 7:15 am with those who started at 8:40 am. They found that students who started at 8:40 got higher grades and more sleep on weekday nights than those who started earlier. One in four U.S. high school students admits to falling asleep in class at least once a week.It is known that during human adolescence, circadian rhythms and therefore sleep patterns typically undergo marked changes. Electroencephalogram (EEG) studies indicate a 50% reduction of deep (stage 4) sleep and a 75% reduction in the peak amplitude of delta waves during NREM sleep in adolescence. School schedules are often incompatible with a corresponding delay in sleep offset, leading to a less than optimal amount of sleep for the majority of adolescents. Caffeine
Consumption of caffeine in large quantities can have negative effects on ones sleep cycle. While there are short-term performance benefits to caffeine consumption, overuse can lead to insomnia symptoms or worsen pre-existing insomnia. Consuming caffeine to stay awake at night may lead to sleeplessness, anxiety, frequent nighttime awakenings, and overall poorer sleep quality. Hospital stay
A study performed nationwide in the Netherlands found that general ward patients staying at the hospital experienced shorter total sleep (83 min. less), more night-time awakenings, and earlier awakenings compared to sleeping at home.
The organization recommends healthy sleep habits for ideal cardiac health along with other well known factors like blood pressure, cholesterol, diet, glucose, weight, smoking, and physical activity. The Centers for Disease Control and Prevention has noted that adults who sleep less than 7 hours per day are more likely to have chronic health conditions including heart attack, coronary heart disease, and stroke compared to those with adequate amount of sleep.In a study that followed over 160,000 healthy, non-obese adults, the subjects who self-reported sleep duration less than 6 hours a day were at an increased risk for developing multiple cardiometabolic risk factors. They presented with increased central obesity, elevated fasting glucose, hypertension, low high-density lipoprotein, hypertriglyceridemia, and metabolic syndrome. The presence or lack of insomnia symptoms did not modify the effects of sleep duration in this study.The United Kingdom Biobank studied nearly 500,000 adults who had no cardiovascular disease, and the subjects who slept less than 6 hours a day were associated with a 20 percent increase in the risk of developing myocardial infarction (MI) over 7 years of follow-up period. Interestingly, long sleep duration of more than 9 hours a night was also a risk factor. Immunosuppression
Among the myriad of health consequences that sleep deprivation can cause, disruption of the immune system is one of them. While it is not clearly understood, researchers believe that sleep is essential to providing sufficient energy for the immune system to work and allow inflammation to take place during sleep.