Effects of time, sex, ethnic origin, and area of residence on prevalence of asthma in Israeli adolescents.

Objectives: To study effects of time, sex, ethnic origin, and area of residence on prevalence of asthma in Israeli adolescents.

Design: Retrospective survey of asthma from computerised medical draft records of conscripts examined up to the end of 1989.

Setting: Five regional centres in Israel.

Subjects: 443 186 conscripts (262 836 males and 180 350 females) aged 17-18 who were born over a nine year period.

Main Outcome Measures: Asthma determined by medical history, physical examination, and lung function tests at rest and after exercise.

Results: Asthma was more prevalent in males than females (26.5/1000 v 21.4/1000, relative risk 1.25 (95% confidence interval 1.19 to 1.32)). Subjects were split into three groups according to year of birth, and prevalence of asthma increased over time from 18/1000 to 24/1000 to 36/1000 (risk of asthma 0.56 (0.54 to 0.59) for first birth group relative to last birth group and 0.69 (0.66 to 0.72) for second group relative to last group). Risk of asthma was also affected by ethnic origin (highest for Western origin and lowest for north African origin, relative risk 1.63 (1.56 to 1.71)) and area of residence (highest in the central coastal region--risk of 1.24 (1.19 to 1.30) relative to the north coastal region--and lowest in inland areas--risk of 0.67 (0.64 to 0.70) relative to north coastal region).

Conclusions: Prevalence of asthma in Israel is increasing and is higher in males, in people of Western origin, and in those living in the most industrialised coastal region.