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All night EEG sleep patterns were recorded for 3 consecutive nights in 7 hypothyroid patients and compared to those of normal subjects of the same ages. No differences were noted between the patients and controls in the percentage for rapid eye movement (REM) sleep, total sleep time, time required to fall asleep, intervals between REM periods and number of REM periods for a given night. The most consistent and striking finding was that the percentage of time spent in stages 3 and 4 sleep was markedly reduced in all hypothyroid patients. The young adult hypothyroid patients showed a significant decrease in stage 4 sleep compared to normal young adult subjects, whereas the elderly hypothyroid patients had a significant decrease in stage 3 sleep compared to normal elderly subjects. Four of the 7 patients were again studied after several months of therapy with desiccated thyroid when they were euthyroid. After treatment, the percentage of time spent in stages 3 and 4 increased for each patient so that the levels for these sleep stages were no longer significantly lower than those of the controls. Also, after treatment the waking alpha EEG frequency increased slightly for each subject and there was improvement in psychological test performance. The findings indicate that, in hypothyroidism, stages 3 and 4 sleep are significantly decreased. The results also are suggestive that treatment with desiccated thyroid may produce an increase in these sleep phases. Auditory awakening thresholds for these sleep stages are higher than in other sleep periods, so that by this criterion they are “deeper” stages of sleep. It may be that a reduction in stages 3 and 4 sleep directly relates to patients' feeling that they have slept little and/or poorly.
Kales et al. (Wed,) studied this question.