Japanese and Western diet and risk of idiopathic sudden deafness: a case-control study using pooled controls

Background One of the proposed aetiological mechanisms for idiopathic sudde n deafness is vascular disease. However, it is not known whether traditiona l cardiovascular risk factors, such as particular dietary factors, are asso ciated with this condition. Methods A case-control study using pooled controls was conducted in Japan t o investigate the relationship between idiopathic sudden deafness and diet. An m:n matched-pairs method was used to obtain age-, gender- and residenti al district-matched controls from a nationwide database of pooled controls. Food intake was assessed from a self-administered usual food frequency que stionnaire that asked about intake of 35 foods (including four drinks). Par ticipants were classified according to the frequency of intake of Western f oods and the frequency of intake of traditional Japanese foods. Subgroup an alyses were performed using audiometric subtypes of idiopathic sudden deafn ess. Results Data were obtained for 164 cases and 20 313 controls. An increased risk of sudden deafness was observed among participants who frequently cons umed Western foods (OR = 1.82, 95% CI:1.14-2.89), and a decreased risk of t his condition was observed among participants who frequently consumed Japan ese foods (OR = 0.52, 95% CI : 0.33-0.82), A direct association of sudden d eafness with Western food intake was evident for flat-type hearing loss. Conclusion This study suggests that a largely Western diet might be a risk factor for idiopathic sudden deafness, a traditional Japanese diet might be a preventive factor for this condition, or both. These findings are consis tent with the hypothesis that vascular factors are an important cause of id iopathic sudden deafness, although the possibility of residual confounding by unmeasured confounders such as socioeconomic status cannot be ruled out.