Design: Retrospective longitudinal cohort
Population: 360 adult cochlear implant recipients grouped by contralateral hearing
Primary outcome: Device use and word recognition over 12 months
Effect: Full-time use 50% (SSD) vs 82% (bilateral); limited use OR 4.38 (2.03 to 9.48)

This single-centre cohort compared 360 adult cochlear implant recipients by hearing in the other ear: single-sided deafness (81), asymmetric loss (41) and bilateral non-serviceable loss (238), using processor datalogging and word recognition over the first year.

Full-time use (8 hours or more a day) was reached by 50% with single-sided deafness vs 82% with bilateral loss. Single-sided deafness was the only independent predictor of limited use (OR 4.38, 95% CI 2.03 to 9.48). Word scores stayed lower through 12 months and did not reach the 50% responder threshold. One-month performance predicted the 12-month result in the other groups, but not in single-sided deafness. Use converged by about 12 months.

With a good ear on the other side, the implant has to compete, so early engagement is harder and early scores are not a reliable guide. This argues for specific counselling before surgery and closer support in the first six months, not against implanting single-sided deafness.

Counsel single-sided deafness candidates that full-time use and speech gains typically come more slowly.
Monitor datalogging closely in the first 6 months and intervene early if use is limited.
Do not use one-month scores to predict final outcome in single-sided deafness.
Build auditory training that isolates the implanted ear into the rehabilitation plan.

Why it matters

Single-sided deafness is a growing indication, and its rehabilitation does not behave like bilateral loss.

The statistics, in plain English

An odds ratio of 4.38 means the odds of limited use were about four times higher with single-sided deafness. The interval (2.03 to 9.48) is wide but stays well above 1.