Fluoride Action Network


There are no studies of oral health and esophageal cancer in Africa, or of this area’s endemic dental fluorosis, an irreversible enamel hypo-mineralization due to early-life excessive fluoride. During 2014-18, we conducted a case-control study of squamous cell esophageal cancer in Eldoret, western Kenya. Odds ratios (AORs (95% confidence intervals)) were adjusted for design factors, tobacco, alcohol, ethnicity, education, oral hygiene and missing/decayed teeth. Esophageal cancer cases (N=430) had poorer oral health and hygiene than controls (N=440). Compared to no dental fluorosis, moderate/severe fluorosis, which affected 44% of cases, had a crude OR of 20.8 (11.6, 37.4) and on full adjustment was associated with 9.4-fold (4.6, 19.1) increased risk, whilst mild fluorosis (43% of cases) had an AOR of 2.3 (1.3, 4.0). The prevalence of oral leukoplakia and tooth loss/decay increased with fluorosis severity, and increased cancer risks associated with moderate/severe fluorosis were particularly strong in individuals with more tooth loss/decay. Using a mswaki stick (AOR=1.7 (1.0, 2.9)) rather than a commercial tooth brush and infrequent tooth brushing also independently increased risk. Geographic variations showed that areas of high esophageal cancer incidence and those of high groundwater fluoride levels have remarkably similar locations across Eastern Africa. In conclusion, poor oral health in combination with, or as a result of, high-altitude susceptibility to hydro-geologically influenced dental fluorosis may underlie the striking co-location of Africa’s esophageal cancer corridor with the Rift Valley. The findings call for heightened research into primary prevention opportunities of this highly fatal but common cancer.

Author Information:

Menya D. and  Ayuo P. – School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya.

Maina SK. and Kigen N. –  Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya.

Kibosia C., Oduor M., Some F., Chumba D. – School of Medicine, College of Health Sciences, Moi University, Eldoret, Kenya.

Oduor M. and Osano O.  – University of Eldoret, Eldoret, Kenya.

Middleton DR. and Schuz J. – Section of Environment and Radiation, International Agency for Research on Cancer, Lyon, France.

Abedi-Ardekani B. and McCormack V. – Section of Genetics, International Agency for Research on Cancer, Lyon, France.