Sleep called key to health

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Sleep is an index of health and should be considered as "essential to a healthy lifestyle as exercise and nutrition," two neurologists at Northwestern University said yesterday in an editorial in Archives of Internal Medicine.

Dr. Phyllis C. Zee and Fred W. Turek made their observation after reviewing a series of reports in this week's issue of that journal, which focused on how sleep is linked to both physical and mental health.

Among the findings:

• In an international survey of nearly 17,500 university students from 24 countries, "short sleep duration" -- or fewer than seven hours nightly -- was related to poorer self-reported health in young adults.

Among U.S. students, who reported a mean sleep duration of nearly 7.2 hours, less than 5 percent assessed their health as poor. But in Japan, where students said they typically slept for 6.2 hours, and in Korea, where the average was 6.8 hours, 43 percent to 46 percent of students said they were in poor health.

Previous studies of middle-aged and elderly persons indicated that sleep duration of less than seven hours and of more than eight hours is associated with increased mortality. This study of young people found no such health effect from longer sleep duration.

• A study of 161 blacks with type 2 diabetes who had an average age of 57 found that getting fewer hours of sleep or lower-quality sleep was linked to poorer blood glucose control. Most patients reported they slept only six hours and that their sleep was frequently disrupted. Twenty-two percent said they averaged seven hours, and just 6 percent said they averaged eight hours. Higher blood sugar levels were associated with less sleep.

• Persons with sleep-related breathing disorders are significantly more likely to develop depression, another study found. As problems such as labored breathing, frequent pauses in breathing or reduced breathing worsened, the odds of depression worsened. For example, the study showed that increasing sleep apnea from "minimal" to "mild" nearly doubled a patient's risk of becoming depressed.

• Patients with allergic rhinitis, an inflammation of the nasal membranes such as that caused by hay fever, ragweed or other allergens, are more likely to have trouble sleeping and suffer from sleep disorders than those without allergies, French research showed. Sixty-three percent of those with allergic rhinitis said they felt they did not get enough sleep, and 36 percent said they were insomniacs. For controls, those percentages were 25 percent and 16 percent.

Another study in the journal found that those in rural areas who sleep fewer hours appear to have a higher average body mass index than those who sleep more. Similar results had been seen earlier in urban areas.

Other newly published research suggests that the immune system may play a role in narcolepsy, a disorder marked by a sudden and uncontrollable urge to sleep. Another study indicates the immune system may be affected by a lack of sleep, altering blood chemistry in a way that permanently contributes to inflammation and a variety of diseases.

Because of evidence of a "bidirectional relationship between sleep and health," the authors concluded, "assessment of sleep quantity and quality should be integrated into the routine review of systems."