Altitude as a risk indicator of dental fluorosis in children residing in areas with 0.5 and 2.5 mg fluoride per litre in drinking water.

The purpose of this study was to assess the association between altitude and dental fluorosis among Ugandan children in two fluoride (F) districts while controlling for other factors related to fluorosis. A random sample of 481 children aged 10-14 years was examined for fluorosis using the Thylstrup and Fejerskov (TF) index. The prevalence and severity of dental fluorosis increased significantly with increase in altitude (900 vs. 2,200 m in the low- and 1,750 vs. 2,800 m in the high-F district) and in F concentration in the drinking water. In bivariate correlation analyses, F exposure from liquid (FEL), altitude, infant formula, vegetarianism and storing of drinking water in earthenware pots were significantly associated with the tooth prevalence of fluorosis (TPF), i.e. at a severity of TF score >/=1 (p<0.05); age and gender were not. The stepwise multiple linear regression explained 35 and 55% of the variance in TPF within the low- and high-F districts, respectively. The change in R2 due to FEL was 28 and 51% points compared with 5 and 4% points due to altitude. The significant effect of FEL and altitude was confirmed by multiple logistic regression analyses. Thus, although most of the variation in the prevalence and severity of dental fluorosis was explained by the F intake from liquid, altitude was a significant risk indicator after controlling for potential confounders.