/publications/issue/2006/2006-12/2006-12-6134

INSOMNIA WATCH

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Does Zopiclone Hinder Memory?

At least one insomnia medication affects sleep-associated memory function, according to an article published in Neuroscience Research (October 2003). Researchers compared 2 sleep therapies: 0.25 mg zopiclone, a nonbenzodiazepine hypnotic, and 7.5 mg brotizolam, a benzodiazepine hypnotic widely used outside the United States.

In a double-blind, placebo-controlled, crossover study, South American patients learned a list of words an hour before taking a single bedtime dose of the study drug and then attempted to recall the words after awakening the next morning. Brotizolam did not affect word recall, compared with placebo. The patients treated with zopiclone, however, remembered fewer words, compared with the placebo patients. Interestingly, neither agent was found to cause residual (next-day) sedation.

Because they may impair sleep-associated memory storage, nonbenzodiazepine "Z drugs" such as zopiclone may require more study regarding their effect on cognitive function, memory processes, and sleep function.

Insomnia Patients Are Warmer

As the healthy sleeper falls asleep, heat is transferred from the body core to the periphery, resulting in an increase in skin, finger, and foot temperatures.Yet, little has been known about this heat transfer process in poor sleepers. Australian researchers compared finger temperatures in patients with and without insomnia as they initiated sleep. The results of the study were reported in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology (November 2005).

Despite comparable baseline finger temperatures and contrary to the researchers' expectations, the increases in finger temperatures in the patients with insomnia were significantly higher (P = .001), compared with those of the healthy controls. The researchers noted that the insomniacs' core body temperatures also were significantly higher than those of the healthy sleepers. It appears that temperatures and heat transfer processes differ in those who sleep well and in those who sleep poorly, although the researchers believe that this finding requires more research.

Obesity Means Shorter Sleep

Obesity and hormonal changes associated with excessive weight have previously been associated with short sleep. Now a recent study reported in the September 18, 2006, issue of the Archives of Internal Medicine provides more evidence for this observation.

A group of 990 patients in Iowa was studied to determine whether there was a relationship between body mass index (BMI) and short sleep time. Cross-sectional analysis of the rural, adult patients found that self-reported sleep duration on weeknights was negatively correlated with BMI. That is, increased body weight was associated with shorter sleep time. This correlation between high BMI and short sleep remained valid even after adjusting for a variety of key socioeconomic and health factors, such as sex, age, educational level, income, marital status, alcohol use, snoring, and depression.

Poor Sleep Predicts Suicide

In a study reported in the European psychiatric journal Psychiatria Danubina (September 2006), data from the US National Comorbidity Survey were assessed to determine the association between sleep and suicide.

The researchers employed statistical analyses to determine whether average nightly sleep time correlated with suicidal thoughts and actions in >8000 adults aged 15 to 54. After adjusting for demographic factors, they determined that decreased sleep time significantly increased the odds of suicidal thoughts and attempts. Mental disorders also were associated with less sleep, as well as with suicidal ideation and attempts. Yet, these disorders did not significantly influence the relationship between less sleep and suicide.

Thus, poor sleep appears to increase the likelihood of both suicidal thoughts and attempts, even after taking into account the effects of comorbid conditions such as depression. The researchers believe that the study results may be used to improve suicide-prevention measures and programs.