Among the three main symptoms of cough, dyspnea and wheezing indicating bronchial asthma, cough and dyspnea are non-specific symptoms that may be caused by other chronic respiratory diseases. Accordingly, the complaints of wheezing by patients and the presence of audible wheezing are important clues to diagnose asthma. Yet, with regard to the reversible airway obstruction as one of the features of asthma, wheezing is also developed reversibly and, as a result, its underdiagnosis is very common in spite of a prior presence of wheezing in the past medical history.

As the old increase, elderly asthmatics have been increasing gradually. But an exact diagnosis of elderly asthmatics may be delayed¹⁾, mainly because of the low frequency in complaining of asthma symptoms, including cough, dyspnea, wheezing and so forth²⁾. We previously reported that elderly asthmatics of 60 years and up do not complain of symptoms of asthma and the frequency of wheezing is significantly lower than that of young-aged patients³⁾. The decrease in complaining of wheezing in the elderly group is attributed to a decline in physical activities, as compared with young/middle-aged groups. In addition, the reduction of perception ability also can be a main reason for less complaints of asthmatic symptoms. However, It is not clear whether wheezing rarely develops in the elderly asthmatics, compared with the young age groups, or that the elderly patients cannot perceive wheezing regardless of its presence. Therefore, this study attempts to reveal the difference between the rate of wheezing development and the wheezing perception by age in the state of bronchoconstriction by conducting the methacholine inhalation in asthmatics.

194 study subjects, who visited the Allergy and Respiratory Departments from January, 1999 to June, 1999, were the subjects of the methacholine challenge test. All of them met the definition of asthma proposed by the American Thoracic Society⁴⁾. The patients with chronic stable asthma were grouped from mild-intermittent to severe-persistent asthma according to the asthma severity scale proposed by the National Asthma Education and Prevention Program⁵⁾. They had no history of upper respiratory tract infection during the four weeks prior to the study. Asthmatics were classified into three groups by age: Young Group (20–39 years old), Middle-aged Group (40–59 years old), Old Group (of 60 years and up).

Asthma in the elderly, being the subject of much concerns due to an increase in the aged population, can be characterized by a delay in diagnosis, a difficulty in identifying due to considerable complications with other diseases and poor treatment. The primary reason for these characteristics is that elderly patients cannot perceive their symptoms exactly. This study compared an old-aged group with young and middle-aged groups to confirm whether the decrease in wheezing complaints by the old is attributed to underdevelopment of airway obstruction by stimulation, or lower incidence of audible wheezing based on the airway obstruction even at the similar level, or poor perception of the old regardless of the same rate of wheezing development. To this end, the patients were checked by auscultation for the presence of wheezing during the methacholine inhalation to survey if they can perceive wheezing or not. As a result, the rate of wheezing development was discovered not to be different by age and there were no differences of FEV1 value and methacholine concentration value according to wheezing. It was found, in consequence, that there exist no differences by age in the airway reaction to stimulation and the rate of wheezing development.

In this study, around 87% of positive patients during the methacholine provocation test expressed wheezing development, regardless of age difference. Some former studies reported that, among positive patients under the methacholine provocation test, 48%⁶⁾ and about 75%^{7, 8)} expressed wheezing, the frequency of which was higher than ours. This difference is due to the fact that this study adopted a tidal breathing method as the method for the methacholine challenge test rather than the intermittent breathing method in other studies and that subjects of this study are all asthmatics rather than only the patients showing the positive findings in the methacholine test being the subjects of other studies. Therefore, there is a difficulty in making a direct comparison between this study and other studies. Even in the non-wheezing group, however, FEV1% fall and FEV1% after inhalation of the final methacholine concentration did not show differences from those in the wheezing group. This means that the presence of wheezing cannot be explained solely with the change of lung fuctions; it is related to a previous report insisting that air flow limitation plays an important role in developing wheezing and yet a geometrical change accompanying some pressure changes cannot be excluded from the cause of the development of wheezing^{9, 10)} Therefore, it is considered that other factors will decide the presence of wheezing, in addition to the bronchoconstriction affecting lung volume or pressure, such as functional residual capacity, types of respiration or differences of airway deformity by vital action of abdominal muscle, even though we did not measure additionally.

One of the disputable points in this study may be the observational method of wheezing. First, the presence of wheezing was not objectified. According to the traditional definition of wheezing, it indicates a sound more than 400 mHz over 250 millisecond¹¹⁾ while, as this study adopts a judgment of wheezing by stethoscope only, it may not be accurate. However, it is well known that wheezing can be easily detected by stethoscope and it is almost coincident with the equipment method as to the confirmation of the presence of wheezing⁶⁾. Considering such a fact, these differences in adopted methods are deemed to be a matter of secondary importance. Second, we adopted a deep breath at a normal respiratory speed as the type of respiration in stethoscoping. Such type of respiration was, however, difficult to standardize. Even a healthy person can develop wheezing by forced expiration at the level of a little lung volume¹²⁾. It is accordingly, considered that every patient has a different possibility for the development of wheezing based upon expiratory flow rate and lung volume during stethoscoping. As the use of a stethoscope is a generally accepted way of examination to in deep breathing at a normal respiratory speed and it does not need any special effort, it is believed not to cause any significant difference in comparing and observing the presence of a wheezing.

This study reveals that FEV1 value turned out significantly lower in inverse proportion to the rise of age, indicating that the older a patient concerned is, the lower is basal FEV1. Though every patient did not undergo the survey for morbidity period of asthma, it is assumed that such a period must be long in the case of the old. The resultant airway remodeling¹³⁾ might proceed to provoke irreversible airway obstruction. On the other hand, PC20 value was found not to be different by age, which accords with a report stating that airway response to the methacholine does not decrease in the old¹⁴⁾. The presence of wheezing did not appear differently by age and FEV1% fall and FEV1% at the initial detection of wheezing were not different by age. It indicates that there was no difference in the threshold of a wheezing such as a possibility of developing wheezing, by bronchoconstriction at certain degree, as well as in the bronchial hyperreactivity among age groups. Nevertheless, the reason for the lower frequency of wheezing in the old is the low perception level of wheezing. It can be analyzed that low frequency of wheezing in respect of the previous history is due to the reduction of the physical ability to perceive wheezing, rather than the reduction of intellectual faculties like memory. A hearing reduction with aging is highly possible as a primary reason for not perceiving a wheezing, even though this study does not cover the tests for hearing or intellectual faculties, including memory.

It is well known that the old are not very well aware of dyspnea^15–16). In case of acute asthmatic attack, this reduced awareness of dyspnea tends to delay treatment and thereby, might develop into a fatal asthmatic attack. However, this thesis suggests that it is requisite for study on a diagnosis of wheezing in the elderly asthmatics to take an effort to figure out the objective changes, including physical examinations and lung function tests, rather than an inquiry into the case history for the presence of wheezing.

In conclusion, wheezing complaints are not well noticed in the elderly asthmatics due to low perception of wheezing compared with younger asthmatics. There were no differences of bronchoconstriction by stimulus or wheezing developed by bronochoconstriction among young, middle-aged and old groups. More efforts should, hence, be made to closely examine the physiologic variations closely in diagnosing the elderly asthmatics, regardless of a prior medical history of wheezing.