Subjective sleep characteristics of 1,485 males and females aged 50-93: effects of sex and age, and factors related to self-evaluated quality of sleep.

BACKGROUND: This epidemiologic study cross-sectionally examined the effects of sex and age on subjective characteristics of sleep and the factors related to self-evaluated sleep quality in a Dutch noninstitutionalized elderly population. METHODS: 1,692 sleep questionnaires were mailed to all attenders of the general practice serving Krimpen aan de Lek, The Netherlands, aged 50 or over. Both target population and responders (1,485 subjects) were virtually representative of the Dutch population regarding sex and age (50 +) characteristics. RESULTS: Overall, females reported significantly poorer quality of sleep, longer sleep latencies, more nighttime awakenings, less frequent napping, and more frequent use of sedative-hypnotic drugs when compared to males. Additionally, there was a female predominance in the prevalence of disturbed sleep onset and sleep maintenance, whereas a male predominance was observed in the prevalence of excessive daytime sleepiness. Across subjects, a significant age-related increment was found for sleep latency time and time spent in bed. The number of nighttime awakenings increased significantly with age only in males. No significant correlations were found between health status and sex, age, or subjective sleep quality. The most frequently reported causes of disturbed sleep onset and sleep maintenance were worries and nocturia, respectively. Subjective quality of sleep was mostly associated with self-estimated sleep latency. CONCLUSIONS: Our findings extend those of previous epidemiologic studies reporting that sleep disorders are common in the general elderly population. Future studies should further elucidate the nature and extent of geriatric sleep disorders to satisfy the increasing need for its accurate diagnosis and treatment.

Parameters affecting gap detection in the rat.

The present research used a startle amplitude reduction paradigm to investigate the ability of the rat's auditory system to track rapidly changing acoustic transients. Specifically examined was the ability of brief gaps in otherwise continuous noise to reduce the amplitude of a subsequently elicited acoustic startle reflex. The duration of the gap, time between gap offset and startle elicitation (the interstimulus interval or ISI), and rise-fall characteristics of the gap were systematically varied. Consistent with previous research, gaps reliably reduced startle amplitude. Gaps 2 msec long were reliably detected, and a 50-msec ISI resulted in the greatest amplitude reduction. Gaps presented at short ISIs produced amplitude reduction that followed a different time course than did gaps presented at longer ISIs. These results may reflect differences in the length of time available for the processing of the stimulus and may involve two different processes.