FLUORIDATION EXPOSURE STATUS BASED ON LOCATION OF DATA COLLECTION IN THE CANADIAN HEALTH MEASURES SURVEY: IS IT VALID?

Background: Statistics Canada's population health surveys may be an important source of up-to-date evidence on fluoridation and population oral health. The objective of this study was to examine the validity of a geographic measure of fluoridation from a national survey (based on site of data collection), by comparing it with estimates of fluoride level from urine samples.

Methods: The data source is the environmental urine subsample (n=2563) from Cycle 2 (2009-2011) of the Canadian Health Measures Survey. Mean comparison and multivariable linear regression were used to examine whether urinary fluoride levels differed between respondents classified as "fluoridated" versus "non-fluoridated" based on data collection site.

Results: Respondents who attended data collection sites classified as fluoridated had significantly higher mean urinary fluoride levels than those who attended sites classified as non-fluoridated. This effect was robust to adjustment for covariates and was somewhat stronger among an "exposed" subpopulation (defined based on tap water consumption and residential history) compared with a non-exposed subpopulation. No apparent added value was associated with using a more precise geographic indicator based on home postal code.

Conclusions: Fluoridation status based on data collection site seems crude, but is actually reasonably accurate compared with fluoride level in urine, in the context of a large national Canadian survey of urban and rural residents. Although findings are of limited use for individual-level risk assessment, they may be of interest to dental public health researchers and to those engaged in public health surveillance, because they inform efficient and readily available options for monitoring fluoridation status in populations.