Autism prevalence and precipitation rates in California, Oregon, and Washington counties.
OBJECTIVE
To investigate empirically the possibility of an environmental trigger for autism among genetically vulnerable children that is positively associated with precipitation.


METHODS
We used regression analysis to investigate autism prevalence rates and counts first in relation to mean annual county-level precipitation and then to the amount of precipitation a birth cohort was exposed to when younger than 3 years, controlling for time trend, population size, per capita income, and demographic characteristics. In some models, we included county fixed-effects rather than a full set of covariates.


METHODS
Counties in California, Oregon, and Washington.


METHODS
Children born in California, Oregon, and Washington between 1987 and 1999. Main Exposure County-level precipitation.


METHODS
County-level autism prevalence rates and counts.


RESULTS
County-level autism prevalence rates and counts among school-aged children were positively associated with a county's mean annual precipitation. Also, the amount of precipitation a birth cohort was exposed to when younger than 3 years was positively associated with subsequent autism prevalence rates and counts in Oregon counties and California counties with a regional developmental services center.


CONCLUSIONS
These results are consistent with the existence of an environmental trigger for autism among genetically vulnerable children that is positively associated with precipitation. Further studies focused on establishing whether such a trigger exists and identifying the specific trigger are warranted.
Waldman
Michael
M
Johnson Graduate School of Management, Cornell University, Ithaca, NY 14853, USA.
Nicholson
Sean
S
Adilov
Nodir
N
Williams
John
J
D000293:Adolescent; D001321:Autistic Disorder / Q000453:epidemiology* / Q000209:etiology* / Q000235:genetics; D002140:California / Q000453:epidemiology; D002391:Catchment Area, Health; D002648:Child; D002980:Climate; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D009922:Oregon / Q000453:epidemiology; D015995:Prevalence; D014861:Washington / Q000453:epidemiology