Association of water fluoride and urinary fluoride concentrations with attention deficit hyperactivity disorder in Canadian youth

• Published in: Environment international 2019-12, Vol.133 (Pt B), p.105190-105190, Article 105190
• Main Authors: Riddell, Julia K., Malin, Ashley J., Flora, David, McCague, Hugh, Till, Christine
• Format: Article
• Language: English
• Subjects: Adolescent; Attention Deficit Disorder with Hyperactivity - chemically induced; Attention Deficit Disorder with Hyperactivity - epidemiology; Attention deficit hyperactivity disorder (ADHD); Canada - epidemiology; Canadian Health Measures Survey (CHMS); Child; Community water fluoridation; Cross-Sectional Studies; Female; Fluorides - analysis; Health Surveys; Humans; Logistic Models; Male; Mexico; Prospective Studies; United States; Urinary fluoride; Water - chemistry
• ISSN: 0160-4120; 1873-6750; 1873-6750
• DOI: 10.1016/j.envint.2019.105190

•UFSG did not significantly predict ADHD diagnosis or ADHD-type symptoms.•Higher tap water fluoride was associated with higher odds of an ADHD diagnosis.•Higher water fluoride was associated with more ADHD-type symptoms for adolescents.•Adolescents living in a fluoridated region had higher odds of an ADHD diagnosis.•Adolescents living in fluoridated regions had more ADHD-type symptoms. Exposure to fluoride has been linked with increased prevalence of attention deficit hyperactivity disorder (ADHD) in the United States and symptoms of inattention in Mexican children. We examined the association between fluoride exposure and attention outcomes among youth living in Canada. We used cross-sectional data collected from youth 6 to 17 years of age from the Canadian Health Measures Survey (Cycles 2 and 3). Urinary fluoride concentration adjusted for specific gravity (UFSG) was available for 1877 participants. Water fluoride concentration measured in tap water samples was available for 980 participants. Community water fluoridation (CWF) status was determined by viewing reports on each city’s website or contacting the water treatment plant. We used logistic regression to test the association between the three measures of fluoride exposure and ADHD diagnosis. Linear regression was used to examine the relationship between the three measures of fluoride exposure and the hyperactivity/inattention score on the Strengths and Difficulties Questionnaire (SDQ). UFSG did not significantly predict ADHD diagnosis or hyperactive/inattentive symptoms. A 1 mg/L increase in tap water fluoride level was associated with a 6.1 times higher odds of an ADHD diagnosis (95% CI = 1.60, 22.8). A significant interaction between age and tap water fluoride level (p = .03) indicated a stronger association between tap water fluoride and hyperactivity/inattention symptoms among older youth. A 1 mg/L increase in water fluoride level was associated with a 1.5 SDQ score increase (95% CI: 0.23, 2.68, p = .02) for youth at the 75th percentile of age (14 years old). Similarly, there was a significant interaction between age and CWF. At the 75th percentile of age (14 years old), those living in a fluoridated region had a 0.7-point higher SDQ score (95% CI = 0.34, 1.06, p