OBJECTIVE: To assess the dose response of fluoride exposure from water and chronic pain.
METHODS: Using a retrospective cohort design, the study was conducted in two sub-districts of San Kamphaeng district, Poo-kha and On-tai. Five hundred and thirty-four residents aged ?50 years of age were interviewed about their sources of drinking water and assessed for chronic pain. Each water source was sampled for fluoride measurement, from which the average daily fluoride dose was estimated. Binary logistic regression with forward stepwise (likelihood ratio) model selection technique was used to examine the association between the average daily fluoride dose and chronic pain.
RESULTS: We found associations between the average daily fluoride dose and lower back pain [odds ratio (OR) = 5.12; 95% confidence interval (CI), 1.59-16.98], and between the high fluoride area vs. the low fluoride area (OR = 1.58; 95% CI, 1.10-2.28; relative risk= 1.22 with 95% CI, 1.14-1.31) to lower back pain. Other risk factors, such as family history of body pain and a history of injury of the lower body, were also associated with lower back pain. However, there were no relationships between the average daily fluoride dose and leg and knee pains.
CONCLUSION: To prevent further lower back pain, we recommend that the water in this area be treated to reduce its fluoride content.