© 1962 The Royal College of Psychiatrists
The Subjective Assessment of Normal Sleep Patterns
From the Dundee Royal Mental Hospital and the Department of Psychiatry, University of St. Andrews
ABSTRACT
Summary and Conclusions: Before drawing any conclusions from our data we must first recognize the limitations of this type of enquiry. The 2,446 subjects who co-operated in the enquiry did not by any means constitute a randomly selected sample of the community and their responses cannot be taken as representative of the normal population as a whole. In formulating the questionnaire we attempted to minimize the subjective nature of the responses but our findings are still open to the usual criticisms applicable to all surveys involving an impersonal questionnaire approach. Although one might object that the individual may misrepresent his actual sleep habits in his own introspective report, the same objection might be levelled at much of the information obtained in clinical interviews. In any clinical investigation we find ourselves partly dependent on the patient's subjective assessment of his own symptoms. One might argue that the phenomenon of sleep is particularly vulnerable to subjective error and indeed, some investigations, using objective methods of measurement such as the EEG, have demonstrated the discrepancy between subjective and objective assessment of sleep disturbance. If it were further established that the tendency to over estimate sleep disturbance increases sharply with age and is more prevalent in women than men, the reliability of our data would obviously be affected. As yet, however, there is no objective evidence to support such an argument. One might also note that investigation of the sleep pattern by external observation and objective methods of measurement themselves introduce an artificial variable which may disturb the normal sleep pattern. Nevertheless, we must be cautious in interpreting our subjects' reports regarding their sleep in too literal a manner. The information in this survey allows us to report with some confidence on the way in which individuals view their own sleep habits, and the information might also be thought to have a higher objective reliability than the pure assumptions which are normally made on this subject.
The study has certainly suggested that any evaluation of the normal sleep pattern must necessarily take into account the variations due to such factors as age, sex and social class. Our findings support the generally held opinion that as people grow older their sleep pattern changes. This change appears to include a reduction in the number of hours slept, an increase in the time taken in getting off to sleep and a greater tendency for sleep to be light and easily disturbed by frequent night wakening. At the same time we have noted that as age advances people tend to complain less of morning tiredness. It is possible that, as age advances, people do not subjectively experience any great harm from the change in their sleep pattern, and that, as we grow older, we require less sleep. The variation of the sleep pattern with age is much more marked in the case of the female subjects of our sample. Although the two sexes do not differ significantly in the average number of hours slept, there are a number of significant variations in the form which their sleep takes. In general the sleep pattern of the female tends to change earlier than that of the male, usually during middle age. The change in the male sleep pattern with age is not only less marked but tends to be fully established later—some time after the retiral age of 65 years. We have also seen that the incidence in the use of hypnotics appears to increase rapidly with age but our findings suggest that this increase is almost entirely specific to women, 45 per cent. of whom admitted to taking a regular hypnotic in their 70's. The incidence of reported nervousness is again much higher in the case of women and reaches its peak between the ages of 25 and 44 years. These findings might be, of course, interpreted as merely indicating that men are less inclined to admit to taking a regular hypnotic or to being of a nervous disposition. A positive relationship has been demonstrated between the subjective estimation of nervousness and specific changes in the pattern of sleep as evaluated by the subjects. Those people who describe themselves as being nervous tend to report more difficulty in getting off to sleep and a more disturbed night's sleep. They are also more likely to complain of physical symptoms such as heart conditions, high blood pressure and severe headaches. It would thus seem that our general physical and mental state is reflected in the form and quality of our sleep.
Investigations of this type seem worthwhile in providing some sort of standard upon which an individual's sleep pattern may be more objectively evaluated. It is our intention to follow this investigation with a similar study applied to the patterns of sleep typical of patients receiving psychiatric treatment.