Permanent Threshold Shifts Following a SixMonth Mediterranean Cruise

1
Permanent Threshold Shifts Following a Six-Month
Mediterranean Cruise

• Judi Lapsley Miller, Ph.D.
• Hearing Conservation Team
• NSMRL

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Changes in Hearing

• What happened to sailors hearing on the USS
  Dwight D. Eisenhower (CVN69) after one 6-month
  deployment?
• Are sailors in some Departments and Divisions
  more at risk for significant hearing changes than
  others?

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NSMRL Study 1999-2000

• Measured hearing and otoacoustic emissions before
  and after 6 month deployment
• Enrolled 401 sailors
• 339 sailors completed the study
• Mainly tested Air, Engineering, and Reactor
  Departments

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Study Time Line
Noise Exposed Group
Confirmationaudiogram for shifts
PRE-TESTaudiogram
POST-TESTaudiogram
Control Group (no noise exposure)
PRE-TESTaudiogram
POST-TESTaudiogram
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Significant Threshold Shifts

• Navy criteria
• 15 dB shift at 1, 2, 3, or 4 kHz
• average 10 dB shift at 2, 3, and 4 kHz
• Empirical criteria (based on control group)
• 15 dB shift at 1, 2, 3 kHz, or 20 dB at 4kHz
• multi-frequencies at 2,3 or 3,4 or 2,3,4kHz

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Significant Threshold Shifts

• 38 sailors (11.2) had significant changes in
  hearing
• 15 sailors (18 ears) had permanent changes
• 2 sailors (2 ears) had temporary changes
• 22 sailors (25 ears) were post hoc classified
  with significant changes

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Sailors with significant threshold shifts (STS)
by Department
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Sailors with STS by Division
Shown are only divisions where more than 20
subjects were tested
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Sailors with confirmed Permanent Threshold Shifts
by Department
10
Sailors with confirmed PTS by Division
Shown are only divisions where more than 20
subjects were tested
11
PTS in Sailor from Reactor Dept

• Hearing Loss at 6kHz pre and post test
• Multi-frequency permanent threshold shift at
  2,3,4kHz in left ear
• Age 26
• Length of service4 years

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Summary

• Even after only one deployment, over 11 of
  sailors had significant changes in hearing
• The Reactor Propulsion Division appeared to be
  most at risk for STS and PTS
• Results to be used cautiously
• numbers are small and subject to sampling
  variability
• subjects were not randomly selected across
  Departments and Divisions

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Acknowledgements

• This research was funded by the Office of Naval
  Research
• Thanks to the crew of the USS Eisenhower for
  their cooperation and help with our study
• Thanks to the Hearing Conservation Team at NSMRL
  for helping prepare this presentation