Abstract: Male patients of two hospitals in Belo Horizonte completed a questionnaire during an interview on the day of discharge in order to evaluate sleeping conditions related to noise during the previous night and were retested 24 h later. Patients had a worse perception of sleep at the noisier hospital, the University Hospital of the Federal University of Minas Gerais (N=13), whose internal mean nocturnal noise level was Leq = 53.7 db(A), than at the quieter hospital. Baleia (N = 22), whose intemal mean nucturnal noise level was Leq = 45.5 db(A). Noise was the only sleep-disturbing factor which was statistically significant.
Key words: Sleep, Noise, Patient, Hospital
The quality of sleep is frequently. impaired by the excess of noise of the modern society. Today most research in this field is mainly, devoted to disease-related sleep disorders, focusing on biochemical and pathophysiological deficiencies and does not include environmental factors. Sleep quality in overpopulated cities needs to he better characterized; especially with respect to hospitalized patients since this factor is assumed to be important for patient recovery (1-7).
The extemal diurnal mean noise level, Leq = 69.5 db(A), in the city of Belo Horizonte, State of Minas Gerais, is considered to be excessive (8). In order to compare patient perception of their own sleep,a questionnaire was applied during 1994 to 35 male patients on the internal medicine wards of two public hospital. Baleia, representing a quiet hospital, is situated in a park in the outskirts of the city, and the University Hospital of the Federal University of Minas Gerais (UFMG), a noisy one, is located in the downtown area. Twenty-two of the hospitalized patients were from Baleia and 13 from the University Hospital. The patients selected for study did not present any, disease that would be expected to directly affect sleep, such is psychiatric or respiratory disturbances, and were not users of sleeping or sedative drugs. One difficulty in studying patient sleep in hospitals is to discriminate between the sleep pertubation caused by disease and by medical care. In order to minimize the effect of these variables, in the present study we only, interviewed patients on the eve of discharge, concerning the previous night's sleep. The research protocol was approved by the Hospital Ethics Committee. The patients were 17 to 60 years old, averaging 35.6 years, had a family income of 2.90 minimum wages, and 76% of them had fixed diurnal activities. Patients went to sleep on average at 10:15 p.m. and woke up at 6:33 a.m.
The questionnaire consisted of 24 main items related to the sleep characteristics of the patient's last night at the hospital. The patient was also asked to compare these characteristics with those of his home sleep during the last six months. The interview lasted about 30 min and the retest, 15 min.
The reliability of the response was evaluated by test and retest for 20 of those items 24 h later. The retest was performed by a different interviewer; and the results are listed in Table 1. The agreement between answers was analyzed by the Kappa index, denoted by K (9), and by the agreeement index, po, indicating the proportion of agreement for the total number of cases. po is the simplest and most frequently used index. K is a measure of agreement with desirable properties (9-11). A question was considered to be reliable when there was satisfactory agreement, and the usual cut points are K =0.40 or po = 70% (9- 11). The agreement between test and retest was satisfactory for po in 18 questions (90%) and for K in 15 questions (75%) concerning patient sleep at the hospital (Table 1). Items such as routine for preparation to sleep (28.6%), remembering dreams (17.%), thoughts influenced by dreams (12.5%) and parasomnias in general (28.0%) were not retested for the agreement calculation.
Table 1 - Evaluation of the reliability of the questionnaire designed to determine sleep quality
Data are reported as subjective evaluation in frequencies (%) of all 20 retested items at a sleep questionnaire applied to a total of 35 male patients at two hospitals, on the last night before discharge. Retest agreement (K) and retest agreement index (po) are also reported. Note: Agreement was considered to be satisfactorywhen K>0.40 and Po>0.70.
|Akakening without concentration||17.1||0.53||0.88|
|Early awakening and inability to fall asleep again||31.4||0.39||0.74|
|Latency greater than 20 min to fall asleep||51.4||0.43||0.71|
|Longer sleep needed||40.0||0.54||0.74|
|Not calm enough when going to sleep||23.5||0.59||0.82|
|Pleasure in sleep||48.8||0.26||0.53|
|Sleep perturbation due to medical care||43.0||0.88||0.94|
|Sleep perturbation due to organic diseases||29.0||0.44||0.77|
|Sleep perturbation due to psychological problems||17.0||0.55||0.86|
|Sleep perturbation due to noise||45.7||0.59||0.80|
|Sleep perturbation due to illumination||31.4||0.79||0.91|
|Sleep perturbation due to temperature||22.9||0.47||0.83|
|Sleep perturbation due to presence of or attention to other people||20.0||0.55||0.89|
|Sleep perturbation due to lack of adaptation to the hospital setting||8.6||0.27||0.80|
|Sleeping during the daytime (33 min on average)||54.3||0.66||0.83|
The comparison of frequencies of responses between the two groups of patients at the hospitals or at home was made by the Fisher's exact test and between paired data for each hospital, that is; for the same patient at the hospital and at his residence, by the binomial test (10).
The overall percentage of sleep disturbances per night pooled from both hospitals is shown in Table . The percentages of three modalities of perturbation, which correspond to modalities of insomnia, were elevated. Nocturnal awakening was reported by 91.4% of the patients, occurring on average 2.6 times and uniformly affecting the age range from 17 to 60 years old (no significant Pearson correlation was found between age and nocturnal awakening). Latency of more than 20 min to fall asleep was reported by 51.4% of patients and early awakening and inability to fall asleep again was reported by 31.4% of patients (Table 1).
Sleep was disturbed by medical care in 43.0% of patients, by organic diseases in 29.0%, by psychological problems in 17.0%, and by parasomnias in 28.0% of the patients. However, in terms of environmental conditions; 66.0% of the patients reported disturbed sleep; 45.7% were affect by noise, 31.4% by illumination, 22.9% by temperature, 20.0% by the presence of or attention to other people in the room and 8.6% were affected by lack of adaptation to the hospital setting.
In order to further assess the effect of noise, the sleep evaluation questionnaire was examined separately for the two hospital studied.
At the University Hospital, 61.5% of patients desired a longer sleep duration on the last night, a significantly higher proportion (P<0.05, Fisher's exact test) than the 27.0% value observed for patients at the quieter Baleia Hospital. The agreement between test and retest was moderate, K = 0.54. The two groups were not statistically different in terms of home sleep evaluation for the last six months (Fisher's exact test P>0.05). The retest agreement for the home data was po = 0.65. Sleep length was defined as unsatisfactory by most patients at the University Hospital, where 61.5% desired longer sleep duration, and satisfactory at home, where 75.0% desired equal sleep duration, the difference between the two settings being statistically significant (binoinial test, P<0.07). On the other hand, the sleep length of must patients at the Baleia Hospital was satisfactory in both situations, with 73.7% and 68.4% desiring equal sleep duration at the hospital and at home, respectively, a difference that was not statistically significant (binomial test, P>0.05). The slightly better sleep duration for this hospital than at home indicates the possibility of controlling sleep quality during hospitalization in an appropriate setting.
At the University Hospital 30.8% of the patients reported feeling tired on awakening, a value significantly higher than that for the patients at the Baleia Hospital (4.6%) (Fisher's exact test, P = 0.05). The index of agreement obtained on test repetition for this item was good, po = 89%. The data for sleeping at home during the preceding six months for both patient groups were statistically equal (Fisher's exact test, P>0.05).
For all 23 questions, including 18 reliable items, two unreliable items and three items not retested, the results indicated better sleep for Baleia Hospital patients, except for the item "sleep perturbation due to temperature". This item and "sleep perturhation due to illumination" are the only ones not related to internal hospital noise. However, a significant difference between groups was observed only for three items (Table 2).
There was no diiference between hospitals for any of the possible causes of sleep perturbation; except noise. The possible causes evaluated were: change of occupation during the last year, routine for preparation to sleep, time to go to sleep and to wake up, sleep length, preference for sleeping time, nocturnal
Table 2 - Percentage of the subjective evaluation of 23 sleep perturbations given by patients at two hospitals on the last night before discharge.
The mean nocturnal level of noise at the University Hospital was 53.7 db(A) and 45.5 db(A) at Baleia Hospital.
*P< or = 0.05 compared to University Hospital (Fisher's exact
|Akakening without concentration||23.1||13.6|
|Early awakening and inability to fall asleep again||38.5||27.3|
|Lack of routine preparation to sleep||38.5||22.7|
|Latency greater than 20 min to fall asleep||69.2||40.9|
|Longer sleep needed||61.5||27.3*|
|Not calm enough when going to sleep||30.8||19.1|
|Pleasure to sleep||23.1||63.4|
|Thoughts influenced by dreams||9.1||14.3|
|Sleep perturbation due to illumination||46.2||22.7|
|Sleep perturbation due to lack of adaptation to the hospital setting||15.4||9.1|
|Sleep perturbation due to medical care||53.9||36.4|
|Sleep perturbation due to noise||69.2||31.8*|
|Sleep perturbation due to organic diseases||46.2||18.2|
|Sleep perturbation due to presence of or attention to other people||38.5||9.1|
|Sleep perturbation due to psychological problems||30.8||9.1|
|Sleep perturbation due to temperature||15.4||27.3|
|Sleeping during the daytime||61.5||50.0|
awakening, perturbed awakening, preference for time to wake up, medical care, organic diseases, psychological problems, and other environmental problems, such as temperature, illumination, lodging, lack of adaptation, and presence of or attention to people in the room.
In fact, noise was pointed out by patients as the main sleep-disturbing cause. At the University Hospital this factor was signifcantly greater (Fisher's exact test, P<0.05, Table 2) than at Baleia. There was a moderate agreement (K = 0.59). The difference in quality of sleep at home was not significant between groups (53.9% at the University Hospital and 59.1% at Baleia at least once a month, Fisher's exact test, P>0.05). The agreement index for retest was good, po= 91%.
Most of the patients of both hospitals, who are poor and usually reside in the outskirts of the city, seem to be affected by sleep disturbances induced by noise at home. Since the noise level increases toward the center of town, the sleep perturbation by noise must still be higher, reaching the levels observed at the University Hospital (8).
There was no difference between groups concerning sleep perturbation due to medical care at the hospital or at home (Fishers exact test; P>0.05), although both parameters were slightly higher at the University Hospital. Patient responses presented excellent retest agreement,i.e., K = 0.88 at the hospital, and po = 86% at home.
There was no difference in evaluation either at the hospital or at home concerning sleep perturbation due to organic disease (Fisher's exact test. P>0.05). There was moderate agreement for hospital evaluation, K = 0.44, but poor agreement for home evaluation K = 0.35. However most patients reported greater sleep perturbation due to disease at home at least once a month: 70.0% of patients in the University Hospital and 52.6% at Baleia Hospital. Despite the absence of statistically significant differences, the evaluation of sleep perturbation due to disease in the hospital compared to home seems to indicate that the patients at Baleia were in a slightly more advanced state of recovery than at the University Hospital (Table 2). This finding is consistent with reports suggesting that a better sleep and a lower noise level contribute to a satisfactory immunological response (2;7).
There was no difference between patient groups in terms of psychological sleep perturbation at the hospital or at home (Fisher's exact test, P>0.05). There was moderate retest agreement for the hospital, K = 0.53, and home, K = 0.47, but a slightly smaller number of patients considered to have psychological sleep perturhation was found at Baleia Hospital than at the University Hospital, confirming a better recovery at Baleia Hospital.
Evaluation of sleep perturhations due to noise has been reported in subjective (6,12,13) and objective studies (3,14-16), in which a decrease in the length of stages III; IV and V of deep sleep was observed in the EEG. An important reduction of sleep quality was reported at 45 dB(A), which is the maximum value recommended for diurnal sound levels at residences and at hospitals in Brazil (1,3,17). The mean levels of noise recommended by the World Health Organization and the Brazilian Agency for Technical Regulation (ABNT) are of Leq = 35 and 40 dB(A), respectively (17,18). Even the quieter hospital, Baleia, with a mean nocturnal internal value of Leq = 45.5 dB(A) and a maximal noctumal level of Lmax=50.6 dB(A), obtained by sound level monitoring each min for 500 min, does not present a satisfactory standard at night, the quieter period of the day. However, the overall conditions observed for patient sleep at the University Hospital; with a mean nocturnal internal Leq= 53.7 dB(A) and a maximal nocturnal level of Lmax = 59.1 dB(A); seem to be worse due to a noisy environment. The mean sound levels for the two hospitals were significantly different (P<0.05, Student t-test).
The data presented here show that a noisier environment was linked to a worse perception of sleep quality by patients during the last night before discharge from the hospital.
Acknowledgments: The authors acknowledge the technical support of R.C.D. Gomes, A.C.S. Nunes and A. Silva, and of P.A.S. Alvares from Vitek-Consultoria, for the noise measurements.