Association between latitude and allergic diseases: a longitudinal study from childhood to middle-age.
BACKGROUND
Worldwide variations in allergy prevalence suggest that geographic factors may contribute to asthma. Ecologic studies have suggested that latitude, a marker of UV-B exposure and allergen exposures, may be related to clinical allergies.


OBJECTIVE
To examine the relationship between latitude or UV-B based on self-reported geolocation and allergic sensitization and disease prevalence in Australia.


METHODS
The Tasmanian Longitudinal Health Study is a population-based study of respiratory disease spanning childhood to adulthood. The most recent follow-up included a postal survey of 5,729 participants and a clinical substudy of 1,396 participants. Participants' residential addresses were coded for latitude and linked with the UV-B data from satellite-based observations of atmospheric ozone. Multivariable logistic regression analyses were performed to estimate the associations between latitude or UV-B and allergic diseases.


RESULTS
Most northerly latitude, that is, latitude closest to the Equator, and high current UV-B exposure were associated with increased odds of hay fever, food allergy, and skin sensitization to house dust mites and molds. More northerly latitude and higher UV-B exposure were associated with increased odds of current asthma among atopic individuals contrasting with a reduced odds of current asthma among nonatopic individuals.


CONCLUSIONS
This is the first study, to our knowledge, to demonstrate a differential effect of atopic status on the relationship between latitude and current asthma. Our study demonstrates in a genetically and culturally similar group of individuals that geographic factors may a play role in the development of allergic disease.
Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, School of Population Health, University of Melbourne, Melbourne, Australia.
Vicka
V
Oktaria
Shyamali C
SC
Dharmage
John A
JA
Burgess
Julie A
JA
Simpson
Stephen
S
Morrison
Graham G
GG
Giles
Michael J
MJ
Abramson
E Haydn
EH
Walters
Melanie C
MC
Matheson
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000453:epidemiology / Q000209:etiology; D001315:Australia / Q000453:epidemiology; D002648:Child; D015331:Cohort Studies; D005260:Female; D062305:Geographic Mapping; D005843:Geography; D006306:Health Surveys; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology / Q000209:etiology*; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012882:Skin Tests; D014466:Ultraviolet Rays / Q000009:adverse effects; D014807:Vitamin D / Q000008:administration & dosage
D014807:Vitamin D