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Idiopathic Sudden Deafness : risk factors from a case-control study using pooled controls Mieko Nakamura, MD PhD Nobuo

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

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Idiopathic Sudden Deafness : risk factors from a case-control study using pooled controls Mieko Nakamura, MD PhD Nobuo

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  1. 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

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

  3. Frequencies of sudden deafness in Japan– an increasing trend

  4. Proposed etiological mechanisms • Vascular impairment • Viral infection • Others

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

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

  7. 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

  8. Cases • October 1996 - 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

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

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

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

  12. 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

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

  14. 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

  15. 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

  16. Factor analysis Second factor "Western" foods Line of Equality 9 10 11 3 0.5 "Japanese" foods 2 4 5 19 8 1 31 15 30 12 17 23 27 24 16 25 22 6 7 14 13 34 26 29 18 33 First factor 21 32 20 0.5 0 28 35

  17. “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)

  18. “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)

  19. Odds ratios of sudden deafness for “Western” food intake

  20. Odds ratios of sudden deafness for “Japanese” food intake

  21. Odds ratios of sudden deafness for alcohol intake

  22. Odds ratios of sudden deafness for cigarette smoking

  23. Odds ratios of sudden deafness for sleep duration

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

  25. Westernization of food intake in Japan World War II

  26. 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

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