OBJECTIVE; To use both area-based and household-based measures of socio-economic status (SES) in examining socio-economic differences in dental caries occurrence among 9-year-old New Zealand children, and to determine the extent to which the two types of measure are concordant.
Basic research design: Cross-sectional survey of a random sample of 9-year-old children in the province of Southland, New Zealand. Each child was categorised using a household-based SES measure and an area-based SES measure, and their association with dental caries severity (dmfs and DMFS) was examined.
Results: Of the 600 children sampled, 436 (74.5%) were dentally examined, and complete SES data were available for 388 (64.7%). The concordance between the area-based and household-based measures was very low, with SES ratings coinciding for only 36.6% of children; they differed markedly for 10.8%. Use of both SES measures in combination (and adjusting caries severity data for sex and ethnicity) revealed a consistent pattern whereby children of higher SES had lower dmfs and DMFS scores than those of lower SES, irrespective of the type of measure used. Adjusting the estimates for lifelong exposure to water fluoridation reduced (but did not eliminate) the SES gradients, again, irrespective of the type of measure used, or whether dmfs or DMFS was examined.
Conclusions: The epidemiological description of social inequalities in oral health may be best served by using a combination of area- and household-based SES measures. Each appears to have a part to play in teasing out the nature, extent and aetiology of oral health inequalities.