idiopathic sudden deafness : risk factors from a case-control study using pooled controls mieko...
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Idiopathic Sudden Deafness: risk factors
from a case-control study using pooled controls
Mieko Nakamura, MD PhDNobuo Aoki, MD PhDDepartment of Hygiene
Hamamatsu University School of MedicineJAPAN
Learning objectives
To learn
• Definition of idiopathic sudden deafness
• Analyses using a database of pooled controls
• Qualitative assessment on diet
0
50
100
150
200
1971-1973
1987 1993
/million/year
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 frequencyhearing (20,000Hz)
Low tone frequencyhearing (20Hz)
Scala vestibuliScala 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 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
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)
250Hz 500Hz 1kHz 2kHz 4kHz 8kHz120
dB 0
250Hz 500Hz 1kHz 2kHz 4kHz 8kHz
250Hz 500Hz 1kHz 2kHz 4kHz 8kHz250Hz 500Hz 1kHz 2kHz 4kHz 8kHz 250Hz 500Hz 1kHz 2kHz 4kHz 8kHz
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
1
2
3
45
67
8
31
19
11
910
34
27
15 12 3017
22 1623
24 25
1426
33
28
21
13 29
32
18
20
35
Firstfactor0.50
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
0.0
1.0
2.0
3.0
4.0
Infrequent Moderate Frequent
All types High-frequency Low -frequencyFlat-type Profound Other
Odds ratios of sudden deafness for “Japanese” food intake
0.0
1.0
2.0
3.0
4.0
Infrequent Moderate Frequent
All types High-frequency Low -frequencyFlat-type Profound Other
Odds ratios of sudden deafness for alcohol intake
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 >0 and <2 >=2 units/ day
All types High-frequency Low -frequencyFlat-type Profound Other
Odds ratios of sudden deafness for cigarette smoking
0.0
1.0
2.0
3.0
4.0
0 >0 and <20 >=20 / day
All types High-frequency Low -frequencyFlat-type Profound Other
Odds ratios of sudden deafness for sleep duration
0.0
1.0
2.0
3.0
4.0
<7 >=7 and <8 >=8 hours
All types High-frequency Low -frequencyFlat-type Profound Other
Lifestyle factors and idiopathic sudden deafness
A hypothesisModerate 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
050
100150200250300350400(g
/ capita/ day)
rice meatsWorld 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