Screening for common respiratory diseases among Israeli adolescents

*The first two authors had equal contribution to this article Surgeon General Headquarters, Israel Defense Forces Medical Corps, Faculty of Medicine, Ben Gurion University, Beer Sheba, Israel Correspondence: Dr Yaron Bar Dayan, Israeli Air Force and Faculty of Medicine, Ben Gurion University, Beer Sheba, 16th Dolev Street, Neve-Savion, Or-Yehuda, Israel. Telephone +972-3-6341039, e-mail bardayan@netvision.net.il Y Bar Dayan, K Elishkevits, L Goldstein, et al. Screening for common respiratory diseases among Israeli adolescents. Can Respir J 2004;11(4):298-300.


Source of data
All 17-year old Israeli nationals are obliged by law to appear at the Israel Defense Forces (IDF) recruiting office for medical examination.
Included in the current study are all the nominees for military service between January 1 and December 31, 2001.

Medical surveillance
Military physicians performed the medical examinations in the recruiting office.Medical histories were obtained from the family physicians of most conscripts.During the examination, the subjects were asked to note specifically any diagnoses of medical conditions that they had received in the past.The conscripts were classified according to strictly defined guidelines and regulations.Conscripts with a known respiratory disorder, or with respiratory symptoms such as dyspnea, cough or exercise intolerance, were referred to a trained respiratory physician for a second examination.The second examination included a further detailed history, physical examination, spirometry at rest, and radiological and laboratory tests as needed.All subjects with overt clinical signs and spirometry evidence of severe ©2004 Pulsus Group Inc.All rights reserved

ORIGINAL ARTICLE
airway obstruction also underwent an exercise test.The test was 6 min of treadmill running at 5 km/h, arriving at an incline of 10 degrees, while breathing room air (22°C, 50% relative humidity).Lung function was measured 5 min and 10 min after exercise to determine the percentage of fall in forced expiratory volume in 1 s.

Disease categories
The respiratory disorders were classified into the following categories:

Disease severity
The conscripts were also classified according to the severity of their condition and activity limitation.Seven categories were defined, from very mild disorder with no activity limitation to severe disorder and significant activity limitation, which can prevent recruitment.A sample of this classification is presented in Table 1.

Statistical description
All data were recorded on a computer and analyzed later.These data were used to describe the prevalence of common respiratory disease in a specific population -17-year-old adolescents.Because of the large size of this database, small differences between the sexes were disregarded.

RESULTS
The survey included 94,805 adolescent subjects -36,511 (38.5%) were female and 58,295 (61.5%) were male.Table 2 presents the prevalence of the different respiratory disorders for both sexes.The most prevalent diagnosis was asthma (in 8% of male and 6.8% of female subjects).The four most prevalent diagnoses were graded according to their severity as presented in Table 1.severe.The most prominent differences between sexes were noted in the prevalence of chest deformation, spontaneous pneumothorax and COPD.

DISCUSSION
A systematic description of the prevalence of respiratory disorders among adolescents is not performed routinely.The majority of previous reports studied the incidence of specific disorders within selected, small populations.The present study showed a high prevalence of respiratory disorders among 17-year-old Israeli conscripts.
The most common respiratory diagnosis in the present study was asthma.These results are compatible with recent reports that presented a significant increase in the prevalence of asthma in the pediatric population (2)(3)(4)(5).Asthma prevalence varies between 1.6% and 36.8%, with higher prevalence rates in minority, urban and low socioeconomic status populations (3).Among the possible explanations for the increased prevalence are different diagnostic criteria and changing environmental exposure because of widespread urbanization (4).Approximately 55% of the asthma diagnoses in the present study were graded as moderate to severe, meaning that 55% of these adolescents needed regular, daily treatment and frequently used medical services.
Approximately 5% to 15% of adults in industrialized countries have COPD, defined by spirometry.This disease primarily affects men and women over the age of 45 years.The major cause of COPD is tobacco smoking (1,6).The prevalence of adolescent smoking has been increasing.Cigarette smoking in adolescents has been found to be associated with mild airway obstruction and slowed growth of lung function in both sexes (7).It has also been also suggested that girls are more vulnerable than boys to the effects of smoke on lung function and respiratory symptoms (8).The prevalence of COPD reported in our study among 17-yearold adolescents (one per 100,000 female subjects, three per 100,000 male subjects) has not been reported before.Unfortunately, our database did not include information about smoking habits or secondhand exposure from parents.We can only emphasize the need to further investigate these findings.
Tuberculosis has been defined as one of the leading causes of death in the world (9).More than 25% of adolescents in developing countries are infected (10), but this rate is much lower in developed communities.Although Israel represents an immigrant society, the prevalence of a history of tuberculosis infection in the present study was relatively low.Moreover, 67% had a history of infection in the past but normal lung function at the time of medical examination.
It is noteworthy that the prevalence of both chest deformations and spontaneous pneumothorax was much higher in male adolescents than female adolescents (Table 2), and that 92% of the chest deformations were mild, having no significant effect on lung function.Because of the large size of our database, these sex differences may not be clinically significant.

CONCLUSIONS
The most prevalent respiratory disorder among 17-year-old Israeli conscripts is asthma.One-half of the asthma patients in the present study suffered from moderate to severe disease.The prevalence of other respiratory disorders was much lower.

Table 3
presents the prevalence of the different severity grades.A prominent finding was that approximately 55% of the asthma diagnoses were graded as moderate to Screening for common respiratory diseases Can Respir J Vol 11 No 4 May/June 2004 299 DLCO Diffusion capacity of the lung for carbon monoxide; FEV 1 Forced expiratory volume in 1 s; TLC Total lung capacity

TABLE 3
Bar Dayan et al Can Respir J Vol 11 No 4 May/June 2004 300 Prevalences (%) of severity grades for common respiratory disorders in a screening study of 17-year-old Israeli conscripts