Tinnitus Archive

Tinnitus Archive > Data Sets > 1 > Methods > Subject Selection

Subject Selection


Source of Tinnitus Archive subjects

Data summaries in the Archive are based on data contained in the Tinnitus Data Registry of the OHSU Tinnitus Clinic, Oregon Hearing Research Center.

Patient population of the Oregon Tinnitus Clinic

  • Most patients were referred to the Oregon Tinnitus Clinic by physicians, audiologists, or other health professionals. Individuals who were self-referred were accepted as patients if they had recently been seen by a physician.
  • Patients were routinely referred elsewhere for appropriate medical consultation (without further Oregon Tinnitus Clinic evaluation) if they were found to exhibit any of the following:
    1. Correctible middle-ear disorder
    2. Objective tinnitus (e.g. audible clicking or bruits)
    3. Tinnitus they described as sounding like their heartbeat
  • In addition, patients with bilateral, near-total hearing loss were counselled not to attend the Oregon Tinnitus Clinic as their tinnitus is difficult or impossible to test on account of equipment limitations.

Criteria for inclusion of subjects in the Tinnitus Data Registry

Patients attending the Oregon Tinnitus Clinic were candidates for inclusion in the Registry if they satisfied all of the following requirements:

  1. Were at least 18 years of age
  2. Were able to participate in the Clinic's standard tinnitus test protocol
  3. Completed at least 75% of the items on the set of three written questionnaires
  4. Received a confirmatory interview (conducted by Registry staff) designed to confirm and clarify the patient's answers to the questionnaires
  5. Responded to the tinnitus tests and questionnaires with acceptable reliability
  6. Gave informed consent for their data to be included in the Registry (Informed consent was obtained according to the requirements of the Institutional Review Board, Oregon Health & Science University.)

In practice all but a small number of patients satisfied criteria 1-3, 5 and 6 listed above. Requirement 4 caused a greater number of omissions as there were times when no interviewer was available to conduct the interview.

Selection biases affecting the Registry data

1. Age

The selection criteria explicitly excluded children and adolescents. In addition, tinnitus patients in general tend to belong to the older segments of the population Brown, 1990, thus the Tinnitus Data Registry (and therefore the Archive) contains a relatively high proportion of subjects over the age of 50.

2. Hearing capability

The Oregon Tinnitus Clinic referral policy effectively ruled out patients with near-total hearing loss in both ears (see " Patient population of the Oregon Tinnitus Clinic"). Apart from that omission, patients included in the Registry exhibited a wide range of hearing capabilities, ranging from those with little or no hearing loss to those with substantial hearing losses.

3. Educational level and verbal ability

A small number of non-English-speaking patients were omitted from the Registry (primarily patients from countries other than the U.S.). Among English-speaking patients, those who had relatively poor skills for written communication sometimes responded unreliably on the questionnaires, but the standardized interview tended to correct most oversights or misunderstandings that might have affected the quality of such patients' questionnaire responses.

4. Mental competence

A small number of senile or otherwise unreliable responders were omitted from the Tinnitus Data Registry. Such omissions were allowed only when at least two members of the staff independently assigned a rating of "unreliable" because of inconsistencies, contradictions, or unresolvable ambiguities in the patient's responses.

Additional factors tending to restrict the Tinnitus Data Registry sample

1. Geographic distribution

The Oregon Tinnitus Clinic population is heavily weighted toward individuals from the Pacific Northwest region of the United States, who account for approximately 70% of the total Clinic sample.

2. Racial and ethnic composition

No formal data were obtained concerning the racial or ethnic background of the subjects. Informal observations indicated that the Oregon Tinnitus Clinic population (and therefore the subject sample included in the Registry) was primarily English-speaking and Caucasian. This bias probably reflects the current ethnic and racial representation of the Pacific Northwest states. However, it may also reflect as-yet-undetermined biases affecting the referral patterns for patients attending the Oregon Tinnitus Clinic.

3. Gender bias

The patient population of the Oregon Tinnitus Clinic shows a pronounced gender bias, with males usually outnumbering females in the proportion of about 7:3. In addition, the age distribution for males differs significantly from that for females, with the median ages being 50 years for males and 57 years for females. (Also see: Age and Gender)