Does cold water truly promote diver's ear?

Ninety-seven Japanese military divers from two districts, Mutsu (Northern Japan) and Yokosuka (Central Japan), were examined for the incidence of diver's ear (exostosis of the external auditory canal). The average temperature of sea water of the two districts is different because of their latitude, but the two groups had no significant difference in diving career. The incidence of exostosis in the Mutsu (cold area) group showed a significant increase as the diving career progressed. This tendency was not seen in the Yokosuka (warm area) group. The severity of exostosis increased in divers in both districts. The incidence of exostosis in Mutsu was significantly higher than in Yokosuka. The Mutsu group also showed a higher ratio of exostosis grade 2 than the Yokosuka group. These results may support the hypothesis that cold water facilitates formation of external auditory canal exostosis.