Idiopathic Sudden Deafness : risk factors from a case-control study using pooled controls Mieko Nakamura, MD PhD Nobuo Aoki, MD PhD Department of Hygiene Hamamatsu University School of Medicine JAPAN

Learning objectives To learn Definition of idiopathic sudden deafness Analyses using a database of pooled controls Qualitative assessment on diet

Frequencies of sudden deafness in Japan – an increasing trend

Proposed etiological mechanisms Vascular impairment Viral infection Others

Blood supply in Cochlea Subclavian artery ⇒ Vertebral artery ⇒ Basilar artery ⇒ Anterior inferior cerebellar artery ⇒ Common cochlear artery ⇒ Common modiolar vein ⇒ arterioles and venules intricate capillary beds Cochlea

A schematic drawing of inner ear High tone frequency hearing (20,000Hz) Low tone frequency hearing (20Hz) Scala vestibuli Scala tympani Vestibular apparatus Helicotrema

Aim of a case-control study To know Associations of traditional cardiovascular risk factors Similarities and differences of the associations among types of hearing loss

Cases October August 1998 Patients diagnosed with idiopathic sudden deafness according to criteria established by Japan’s Sudden Deafness Research Committee Having an audiogram within 14 days of onset

Definition of idiopathic sudden deafness Sensorineural hearing loss of sudden onset No involvement of cranial nerves other than the eighth nerve No known etiology

Patterns of hearing loss definition High-frequency hearing loss Low-frequency hearing loss Flat-type hearing loss Profound hearing loss Other

Patterns of hearing loss (mean-SD) 120 dB 0 High-frequency (n=20)Low-frequency (n=31) Flat-type (n=54)Profound (n=20)Other (n=39) Low High

Controls Selected from a database of pooled controls The information in the database was obtained between 1987 and 1994 Matched to cases on age (in five-year bands), gender, and residential district

Questionnaire Identical for cases and controls Food intake frequencies, tobacco, alcohol, sleeping hours, etc

Statistical methods m : n matching Odds ratios and 95% confidence intervals were estimated using conditional logistic regression for group matching, where the matching variables were age, gender, and residential district

Qualitative assessment on diet Frequencies of intake about 31 foods and 4 drinks were obtained New indexes (“Western” food intake and “Japanese” food intake) were created based on principal component factor analysis performed for these data

Factor analysis 0.5 Second factor "Japanese" foods "Western" foods First factor Line of Equality

“Western” food intake Calculated by summing the frequencies of intake for each of the foods in the “Western” food group On the basis of these scores: frequent intake (highest quartile) moderate intake (middle two quartiles) infrequent intake (lowest quartile)

“Japanese” food intake Calculated by summing the frequencies of intake for each of the foods in the “Japanese” food group On the basis of the scores: frequent intake (highest quartile) moderate intake (middle two quartiles) infrequent intake (lowest quartile)

Odds ratios of sudden deafness for “Western” food intake

Odds ratios of sudden deafness for “Japanese” food intake

Odds ratios of sudden deafness for alcohol intake

Odds ratios of sudden deafness for cigarette smoking

Odds ratios of sudden deafness for sleep duration

Lifestyle factors and idiopathic sudden deafness A hypothesis Moderate alcohol intake coagulation ↓ fibrinolysis → Western diet (rich in saturated fatty acids) coagulation ↑ serum cholesterol ↑ Smoking microcirculatory/haemo- static abnormalities vasospasm Heavy alcohol intake fibrinolysis ↓ vasospasm Vascular impairment in cochlea ?

Westernization of food intake in Japan World War II

Summary Increased risks with high intake of "Western" diet high intake of alcohol low intake of traditional “Japanese” diet Similar associations of diet among types of hearing loss