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Epidemiology of nocturnal asthma
Epidemiology
of Nocturnal Asthma
MARGARET TURNER-WARWICK, D.M., Ph.D., F.R.C.P. London,
United Kingdom
To determine the frequency of nocturnal asthma in a non-hospital-based population, a survey was conducted of asthmatic patients being treated by primary care physicians in many parts of the United Kingdom. Seventy-four percent of the 7,729 patients who participated reported awakening at night at least once a week, and 64 percent reported awakening at least three times a week. Of 3,015 patients who regarded their asthma as mild, 26 percent reported awakening every night, suggesting that many patients underestimate the severity of their asthma. Patients with no nocturnal asthma generally had a lower frequency of allergic and nonallergic trigger factors, but no dominant feature distinguished these patients from those who did awaken at night. As perceived asthma severity increased, so did the number of drug types being prescribed, but no particular drug was identified as being associated with a lower frequency of nocturnal asthma. The frequency of nocturnal asthma found in the survey population (74 percent), in which 48 percent of the patients were using corticosteroid aerosols, was identical to that found in a survey conducted in 1971, when this medication was not yet available. Even though the sampling methods used in the two surveys were different, this finding indicates that the introduction of aerosol steroids has had little effect on the frequency of nocturnal asthma. Current use of existing medication alone may not eliminate the problem of nocturnal asthma, and new drugs and/or new dosing strategies may be needed to control this disabling symptom completely.
octurnal asthma is important because most deaths due to asthma occur at night [l] and beN cause regular disturbance of sleep may impair performance during the day. Hospital-based surveys have indicated that awakening at night is very common among asthmatic patients. In two separate surveys [2] conducted at clinics in the United Kingdom, 74 and 61 percent of consecutive asthmatic patients answered affirmatively when asked, “Do you get asthma attacks at night?” The objective of the present survey was to assess the frequency of nocturnal asthma in a non-hospitalbased patient population, namely, patients being treated by their primary care physicians (general practitioners), and to identify the influence of their medication on their nighttime symptoms. PATIENTS AND METHODS Physician and Patient Selection
About 26,000 primary care physicians, located in many parts of the United Kingdom, were sent a letter explaining the purpose of the survey. Enclosed with the letter was an eligibility form and a detailed questionnaire to be completed only for the patients found to be eligible. Information on up to 10 consecutive patients was requested from each physician. Eligibility
The physicians were asked to complete an eligibility form for every patient for whom they had prescribed or represcribed an aerosol bronchodilator. Affiiative answers to the following questions allowed detailed questionnaires to be completed for the patients: (1) Have you had any episodes of “wheezy” breathlessness or chest tightness at any time during the day or night during the past month? (2) Do you get substantial immediate relief using a bronchodilator aerosol? (3) Have these episodes recurred over a period of more than six months? Patients with known hypertension or cardiac disease were not surveyed. Information about airflow measurements was obtained to confirm reversibility but was not considered obligatory because it was anticipated that this information would not be available for many of the patients. Questionnaire
From The Cardiothoracic institute, The Brompton Hospital, London, United Kingdom. Requests for reprints should be addressed to Dr. Margaret Turner-Warwick, The Cardiothoracic Imtiie, The Brompton Hospital, Fulham Road, London SW3 6HP, United Kingdom.
6
July 29, 1988
The American Journal of Medicine
Volume 85 (suppl 1B)
A more detailed questionnaire was completed for each patient fulfilling the eligibility criteria. This questionnaire provided information about symptoms, age at onset of asthma, observed trigger factors, patient assessments of their asthma severity, and current medication. The questions concerned with nocturnal symptoms were: (1) Do you wake up at night with any of the following symptoms: tightness of the chest? wheeziness? coughing? none of these? and (2) If “yes,” how often does this happen: every night? up to three nights per week? up to one night per week? less frequently?
RESULTS Questionnaires
A total of 7,778 questionnaires were returned by 1,199 physicians (a mean of 6.5 per physician), of which 7,729 were analyzable. Some questions were not answered completely, so the total number of answers analyzed for each question varied slightly. Asthma
The disease characteristics of the patient population are given in Table I.
TABLEI DiseaseCharacteristicsof Patients Age at onset of symptoms (n = 6,682) Allergic provoking factor (n = 7,562)
67%under 29 years 78%(dust 56% pollen, 46% animals 25%) 76% 24% 18%smokers 30%ex-smokers 52%never smoked 86%
Wheeze and cough Wheeze only (n = 6,372) Smoking(n = 6,793) Peak flow reversibihty >15% (n = 2,567)
Trigger Factors
The frequency of trigger factors is shown in Figures 1 and 2. There was a lower frequency of allergic and nonallergic trigger factors in the patients with no nocturnal symptoms. No single trigger factor was found to be associated with nocturnal asthma. Frequency of Nocturnal Asthma
Seventy-four percent of the 7,729 patients analyzed reported awakening at least once a week, and 64 percent reported awakening at least three times a week (Table II).
6050(I) E $40 2. 830E L 81
Severity of Asthma and Frequency of Awakening at Night
Overall, there was a good correlation between asthma severity as perceived by the patients and frequency of nocturnal awakening (p,, and (4u percent) were awakening at least tnree nights a week.
NoNAn=
10 -
0
-
Pollens
Foods
Drugs
Figure 1. Allergic provoking factors. NA = nocturnal asthma; no NA = without nocturnal asthma.
Medication
The physicians were found to be prescribing more medications and more types of medication, especially oral corticosteroids and theophyllines, as asthma severity (as assessed by the patient) or the frequency of nocturnal asthma increased, but no drug or drug combination was associated with a significantly lower frequency of nocturnal awakening. In particular, no regimen was identified that substantially increased the proportion of patients having no nocturnal symptoms (Table III).
Animals
n
70
q
NAn=7120
No NAn=481
60
u) so E .$ 40
g
6
30
COMMENTS
E
This survey made no attempt to sample all patients in the United Kingdom with variable airflow obstruction. Such a prevalence study would, of course, require a different design. However, it did attempt to identify a group of patients with variable airflow obstruction receiving at least the most common form of treatment in the United Kingdom, a treatment used even in the mildest cases, namely, an aerosol bronchodilator. Although objective physiologic measurements of airflow were reported for only 55 percent of the patients, we were gratified that this diagnostic tool is being used so widely. Of the 2,567 patients for whom peak flow records were available, 86 percent had a peak flow variability equal to or greater than 15 percent. Other features of our population, including age at onset of asthma (67 percent under the age of 29 years), allergic trigger factors (78 percent positive), and the small number of current smokers (18 percent) are similar to the features of hospital-based populations described previously [2,3].
g *O p” 10 0
h2le
At work
Figure 2. Environmental provoking without nocturnal asthma.
Cold factors.
Damp
Smoke
NA = nocturnal
None
asthma; no NA =
TABLEII Frequencyof Nocturnal Awakening(n = 7,729) Frequency
Percent
Every night At least 3 nights/week At least 1 night/week At least 1 night/month July 29, 1988
The American Journal of Medicine
Volume 85 (suppl 16)
7
SYMPOSIUM
ON ASTHMA/TURNER-WARWICK
TABLE III Medication and Frequency of Nocturnal Awakening (percent of patients) Every Night
2 3 Nights a Week
5 Once a Week but >Once a Month
Never
No treatment Beta-2 agonists Cromolyn Beclomethasone Budesonide Theophyllines Oral steroids
Seventy-four percent of the patients in the present survey reported awakening at least once a week with the symptoms of asthma, a figure very close to the ‘74 percent and 61 percent reported 15 years ago for two separate hospital asthma clinic populations. Thus, the frequency of nighttime asthmas symptoms does not seem to have fallen, despite the introduction of aerosol steroids (used by 48 percent of the patients in the present study but not available in 1971) and the increasing practice of prescribing medication for use on a regular schedule. To keep the questionnaire brief, questions about the amount of drug prescribed or the amount actually taken were not included. Inadequate dosage and lack of patient compliance may be partly responsible for the fact that the frequency of nocturnal asthma did not vary significantly with the type of drug or number of drugs being used. However, the good correlation between patients’ perceptions of the severity of their asthma and the frequency of their nocturnal awakening with the number of drugs and types of drug prescribed demonstrates that more drugs were being prescribed as severity increased. This suggests that the physicians were increasing the patients’ medications appropriately. It seems unlikely that the patients were failing to comply with their regimens as their symptoms became more severe.
8
July 29, 1988
The American Journal of Medicine
Volume 85 (suppl 16)
The conclusions to be drawn from the results of this survey are that awakening at night with asthma symptoms is very common, even in patients under the routine care of their primary care physician, and that nocturnal awakening due to asthma is often overlooked by patients unless they are specifically questioned about it. Furthermore, the drugs currently available and as currently used do not seem to control nocturnal symptoms in many patients as well as is often supposed. It is important that we optimize the use of these drugs and, at the same time, work to develop new and better ones. ACKNOWLEDGMENT I would like to thank the primary care physicians in the United Kingdom who contributed to this survey.
REFERENCES 1. Cochrane GM: Asthma deaths at night. In: Barnes PJ, Levy J, eds. Nocturnal asthma. London: The Royal Socrety of Medwne 1984; 11-15. (International Congress and Symposlum Series No. 73) 2. Turner-Warwick M: The definition and recognitron of nocturnal asthma. In: Barnes PJ, Levy J, eds. Nocturnal asthma. London: The Royal Society of Medicine, 1984; 3-5. (International Congress and Symposium Series No. 73). 3. Hendrick DJ, Davres RJ, D’Souza MF, Pepys J: An analysrs of prick test reactions in 656 asthmatrc patients. Thorax 1975; 30: 2-8.
of Nocturnal Asthma
MARGARET TURNER-WARWICK, D.M., Ph.D., F.R.C.P. London,
United Kingdom
To determine the frequency of nocturnal asthma in a non-hospital-based population, a survey was conducted of asthmatic patients being treated by primary care physicians in many parts of the United Kingdom. Seventy-four percent of the 7,729 patients who participated reported awakening at night at least once a week, and 64 percent reported awakening at least three times a week. Of 3,015 patients who regarded their asthma as mild, 26 percent reported awakening every night, suggesting that many patients underestimate the severity of their asthma. Patients with no nocturnal asthma generally had a lower frequency of allergic and nonallergic trigger factors, but no dominant feature distinguished these patients from those who did awaken at night. As perceived asthma severity increased, so did the number of drug types being prescribed, but no particular drug was identified as being associated with a lower frequency of nocturnal asthma. The frequency of nocturnal asthma found in the survey population (74 percent), in which 48 percent of the patients were using corticosteroid aerosols, was identical to that found in a survey conducted in 1971, when this medication was not yet available. Even though the sampling methods used in the two surveys were different, this finding indicates that the introduction of aerosol steroids has had little effect on the frequency of nocturnal asthma. Current use of existing medication alone may not eliminate the problem of nocturnal asthma, and new drugs and/or new dosing strategies may be needed to control this disabling symptom completely.
octurnal asthma is important because most deaths due to asthma occur at night [l] and beN cause regular disturbance of sleep may impair performance during the day. Hospital-based surveys have indicated that awakening at night is very common among asthmatic patients. In two separate surveys [2] conducted at clinics in the United Kingdom, 74 and 61 percent of consecutive asthmatic patients answered affirmatively when asked, “Do you get asthma attacks at night?” The objective of the present survey was to assess the frequency of nocturnal asthma in a non-hospitalbased patient population, namely, patients being treated by their primary care physicians (general practitioners), and to identify the influence of their medication on their nighttime symptoms. PATIENTS AND METHODS Physician and Patient Selection
About 26,000 primary care physicians, located in many parts of the United Kingdom, were sent a letter explaining the purpose of the survey. Enclosed with the letter was an eligibility form and a detailed questionnaire to be completed only for the patients found to be eligible. Information on up to 10 consecutive patients was requested from each physician. Eligibility
The physicians were asked to complete an eligibility form for every patient for whom they had prescribed or represcribed an aerosol bronchodilator. Affiiative answers to the following questions allowed detailed questionnaires to be completed for the patients: (1) Have you had any episodes of “wheezy” breathlessness or chest tightness at any time during the day or night during the past month? (2) Do you get substantial immediate relief using a bronchodilator aerosol? (3) Have these episodes recurred over a period of more than six months? Patients with known hypertension or cardiac disease were not surveyed. Information about airflow measurements was obtained to confirm reversibility but was not considered obligatory because it was anticipated that this information would not be available for many of the patients. Questionnaire
From The Cardiothoracic institute, The Brompton Hospital, London, United Kingdom. Requests for reprints should be addressed to Dr. Margaret Turner-Warwick, The Cardiothoracic Imtiie, The Brompton Hospital, Fulham Road, London SW3 6HP, United Kingdom.
6
July 29, 1988
The American Journal of Medicine
Volume 85 (suppl 1B)
A more detailed questionnaire was completed for each patient fulfilling the eligibility criteria. This questionnaire provided information about symptoms, age at onset of asthma, observed trigger factors, patient assessments of their asthma severity, and current medication. The questions concerned with nocturnal symptoms were: (1) Do you wake up at night with any of the following symptoms: tightness of the chest? wheeziness? coughing? none of these? and (2) If “yes,” how often does this happen: every night? up to three nights per week? up to one night per week? less frequently?
RESULTS Questionnaires
A total of 7,778 questionnaires were returned by 1,199 physicians (a mean of 6.5 per physician), of which 7,729 were analyzable. Some questions were not answered completely, so the total number of answers analyzed for each question varied slightly. Asthma
The disease characteristics of the patient population are given in Table I.
TABLEI DiseaseCharacteristicsof Patients Age at onset of symptoms (n = 6,682) Allergic provoking factor (n = 7,562)
67%under 29 years 78%(dust 56% pollen, 46% animals 25%) 76% 24% 18%smokers 30%ex-smokers 52%never smoked 86%
Wheeze and cough Wheeze only (n = 6,372) Smoking(n = 6,793) Peak flow reversibihty >15% (n = 2,567)
Trigger Factors
The frequency of trigger factors is shown in Figures 1 and 2. There was a lower frequency of allergic and nonallergic trigger factors in the patients with no nocturnal symptoms. No single trigger factor was found to be associated with nocturnal asthma. Frequency of Nocturnal Asthma
Seventy-four percent of the 7,729 patients analyzed reported awakening at least once a week, and 64 percent reported awakening at least three times a week (Table II).
6050(I) E $40 2. 830E L 81
Severity of Asthma and Frequency of Awakening at Night
Overall, there was a good correlation between asthma severity as perceived by the patients and frequency of nocturnal awakening (p
NoNAn=
10 -
0
-
Pollens
Foods
Drugs
Figure 1. Allergic provoking factors. NA = nocturnal asthma; no NA = without nocturnal asthma.
Medication
The physicians were found to be prescribing more medications and more types of medication, especially oral corticosteroids and theophyllines, as asthma severity (as assessed by the patient) or the frequency of nocturnal asthma increased, but no drug or drug combination was associated with a significantly lower frequency of nocturnal awakening. In particular, no regimen was identified that substantially increased the proportion of patients having no nocturnal symptoms (Table III).
Animals
n
70
q
NAn=7120
No NAn=481
60
u) so E .$ 40
g
6
30
COMMENTS
E
This survey made no attempt to sample all patients in the United Kingdom with variable airflow obstruction. Such a prevalence study would, of course, require a different design. However, it did attempt to identify a group of patients with variable airflow obstruction receiving at least the most common form of treatment in the United Kingdom, a treatment used even in the mildest cases, namely, an aerosol bronchodilator. Although objective physiologic measurements of airflow were reported for only 55 percent of the patients, we were gratified that this diagnostic tool is being used so widely. Of the 2,567 patients for whom peak flow records were available, 86 percent had a peak flow variability equal to or greater than 15 percent. Other features of our population, including age at onset of asthma (67 percent under the age of 29 years), allergic trigger factors (78 percent positive), and the small number of current smokers (18 percent) are similar to the features of hospital-based populations described previously [2,3].
g *O p” 10 0
h2le
At work
Figure 2. Environmental provoking without nocturnal asthma.
Cold factors.
Damp
Smoke
NA = nocturnal
None
asthma; no NA =
TABLEII Frequencyof Nocturnal Awakening(n = 7,729) Frequency
Percent
Every night At least 3 nights/week At least 1 night/week At least 1 night/month July 29, 1988
The American Journal of Medicine
Volume 85 (suppl 16)
7
SYMPOSIUM
ON ASTHMA/TURNER-WARWICK
TABLE III Medication and Frequency of Nocturnal Awakening (percent of patients) Every Night
2 3 Nights a Week
5 Once a Week but >Once a Month
Never
No treatment Beta-2 agonists Cromolyn Beclomethasone Budesonide Theophyllines Oral steroids
Seventy-four percent of the patients in the present survey reported awakening at least once a week with the symptoms of asthma, a figure very close to the ‘74 percent and 61 percent reported 15 years ago for two separate hospital asthma clinic populations. Thus, the frequency of nighttime asthmas symptoms does not seem to have fallen, despite the introduction of aerosol steroids (used by 48 percent of the patients in the present study but not available in 1971) and the increasing practice of prescribing medication for use on a regular schedule. To keep the questionnaire brief, questions about the amount of drug prescribed or the amount actually taken were not included. Inadequate dosage and lack of patient compliance may be partly responsible for the fact that the frequency of nocturnal asthma did not vary significantly with the type of drug or number of drugs being used. However, the good correlation between patients’ perceptions of the severity of their asthma and the frequency of their nocturnal awakening with the number of drugs and types of drug prescribed demonstrates that more drugs were being prescribed as severity increased. This suggests that the physicians were increasing the patients’ medications appropriately. It seems unlikely that the patients were failing to comply with their regimens as their symptoms became more severe.
8
July 29, 1988
The American Journal of Medicine
Volume 85 (suppl 16)
The conclusions to be drawn from the results of this survey are that awakening at night with asthma symptoms is very common, even in patients under the routine care of their primary care physician, and that nocturnal awakening due to asthma is often overlooked by patients unless they are specifically questioned about it. Furthermore, the drugs currently available and as currently used do not seem to control nocturnal symptoms in many patients as well as is often supposed. It is important that we optimize the use of these drugs and, at the same time, work to develop new and better ones. ACKNOWLEDGMENT I would like to thank the primary care physicians in the United Kingdom who contributed to this survey.
REFERENCES 1. Cochrane GM: Asthma deaths at night. In: Barnes PJ, Levy J, eds. Nocturnal asthma. London: The Royal Socrety of Medwne 1984; 11-15. (International Congress and Symposlum Series No. 73) 2. Turner-Warwick M: The definition and recognitron of nocturnal asthma. In: Barnes PJ, Levy J, eds. Nocturnal asthma. London: The Royal Society of Medicine, 1984; 3-5. (International Congress and Symposium Series No. 73). 3. Hendrick DJ, Davres RJ, D’Souza MF, Pepys J: An analysrs of prick test reactions in 656 asthmatrc patients. Thorax 1975; 30: 2-8.