Genetic-environmental interactions in asthma and allergy: a study in a closed population exposed to different environments.
BACKGROUND
Asthma and allergy are common chronic diseases caused by genetic and environmental factors.


OBJECTIVE
To study the effect of different environments on the prevalence of both diseases in an isolated founder population that resettled in different geographic and environmental areas (namely, the genetically homogeneous population that immigrated to Israel from Cochin, India, 50 years ago).


METHODS
Respiratory and allergy symptoms were recorded by a questionnaire. The relative contribution of genetic factors on asthma and allergy was established by comparing Cochin with non-Cochin Jews living in the Jerusalem mountains; the relative contribution of the environment was determined by comparing mountain Cochin Jews with those living in the desert. The study was conducted from January to October 2004.


RESULTS
A total of 983 individuals (481 mountain Cochins, 353 desert Cochins, and 149 non-Cochins) were studied. The overall prevalence of asthma in Cochins was 23.7%; and of allergy, 29.5%. The rate of asthma and/or allergy in Cochins in the mountains was significantly higher than in control non-Cochins. The rates of both asthma and allergy among Cochin Jews in the mountains were significantly higher than those among Cochin Jews in the desert, the former because of a higher prevalence of allergic asthma. The rates of nonallergic asthma and allergy without asthma were similar in both environments.


CONCLUSIONS
Two different asthma and allergy phenotypes were detected that share a distinct genetic background but differ in the environmental influences. Allergic asthma is strongly determined by both genetic and environmental factors, whereas nonallergic asthma or atopy without asthma is determined mainly by genetic factors and is less influenced by environmental factors.
Department of Pediatrics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Einat
E
Yaari
Ziv
Z
Susser
Amnon
A
Lahad
Yaron
Y
Nesher
Sylvia
S
Kachalsky
Asher
A
Tal
Eitan
E
Kerem
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001249:Asthma / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology* / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D004777:Environment; D018703:Founder Effect; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology* / Q000235:genetics*; D007194:India / Q000208:ethnology; D007223:Infant; D007557:Israel / Q000453:epidemiology; D007585:Jews / Q000208:ethnology; D008875:Middle Aged; D010641:Phenotype; D011795:Surveys and Questionnaires; D055815:Young Adult