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SEMENOV ET AL. / EAR & HEARING, VOL. 34, NO. 4, 402–412
requiring the surgical team to replace the device in the same or
opposite ear. The probabilities and costs of these events were
based on clinical outcomes from the CDaCI study.
Microsoft Excel 2010 (Microsoft Corp., Redmond, WA) was
used for decision tree modeling, and STATA version 12 (Stata-
Corp, College Station, TX) was used for all other analyses.
RESULTS
Study Population
A total of 175 childrenwere followed for 72months after CI. Of
these, 60 children were implanted before 18 months, 71 between
18 and 36 months, and 44 after 36 months of age, with a mean
age at implantation of 13.2, 26.4, and 47.0 months, respectively.
Table 1 shows the baseline characteristics of the study population
stratified by age of implantation. The three groups differed by
gender, age at onset of deafness, duration of deafness, four-tone
hearing threshold average (PTA)—a measure of preimplantation
residual hearing, socioeconomic status, baseline HUI scores, and
baseline Bayley psychomotor development index, but were not
significantly different by race, maternal education level, and other
measures of baseline IQ.
Measurement of Health Utility
Children implanted at <18 months of age gained an average
unadjusted health-utility improvement of 0.51 points in the first
6 years after implantation, compared with 0.41 points for the
18- to 36-month group, and 0.34 points for the >36-month age
group at implantation (
p
< 0.0001). Adjusting for differences
in baseline HUI3 scores and controlling for rate of bilateral
implantation using the GEE model led to a 0.49 point health-
utility gain for the youngest group, a 0.44 point gain for the
middle group, and a 0.43 point gain for the oldest group, which
resulted in lifetime projected QALY gains of 10.7, 9.0, and 8.4
QALYs, respectively (Fig. 1, Supplemental Digital Content 2,
TABLE 1. Characteristics of cohorts
Cochlear Implantation
<18 mos (n = 60)
18–36 mos (n = 71)
>36 mos (n = 44)
Characteristics, No.
Age at implantation, mos, mean (SD)
13.2 (2.4)
26.4 (5.7)
47.0 (7.9)
Duration of deafness, mos, mean (SD)†
13.0 (2.8)
25.4 (6.8)
45.2 (8.3)
Female (%)†
25 (42)
36 (51)
31 (70)
Hispanic (%)
7 (12)
18 (25)
11 (25)
Congenital SNHL (%)†
51 (85)
34 (48)
20 (45)
Four-tone hearing threshold average, dB, better ear†
107.5 (16.3)
106.7 (15.3)
99.6 (16.0)
Race, No. (%)
White
49 (82)
48 (68)
34 (77)
Black
4 (7)
9 (13)
2 (5)
Asian
2 (3)
4 (6)
3 (7)
Other
5 (8)
10 (14)
5 (11)
Maternal education, No. (%)
<8th grade
0 (0)
0 (0)
1 (2)
Some high school
1 (2)
5 (7)
5 (11)
Graduated high school
11 (18)
11 (15)
3 (7)
Some college
13 (22)
23 (32)
14 (32)
Completed college
35 (58)
32 (45)
21 (48)
Household income, No. (%)‡
<$15,000
1 (2)
8 (11)
4 (9)
$15,000–$29,000
7 (12)
9 (13)
5 (11)
$30,000–$49,999
8 (13)
20 (28)
10 (23)
$50,000–$74,999
14 (23)
8 (11)
7 (16)
$75,000–$99,999
12 (20)
10 (14)
3 (7)
>$100,000
11 (18)
10 (14)
9 (20)
Income <$50,000†
16 (27)
37 (52)
19 (43)
HUI scores,* mean (SD)
Before implantation†
0.26 (0.14)
0.31(0.17)
0.37 (0.21)
Six years after implantation
0.76 (0.14)
0.72 (0.20)
0.71 (0.17)
Change†
0.51 (0.21)
0.41 (0.24)
0.34 (0.24)
Cognitive status score, mean (SD)
Bayley PDI (<2y)†
96.2 (17.4)
95.0 (18.9)
76.2 (19.0)
Leiter-R Brief IQ (>2y)
113.5 (15.8)
94.8 (16.0)
106.2 (21.0)
Combined**
100.4 (18.1)
95.6 (20.1)
91.4 (25.5)
Bayley PDI, Bayley Psychomotor Development Index; HUI, Health Utilities Index; Leiter-R Brief, Leiter International Performance Scale-Revised; SNHL, sensorineural hearing loss.
*Health Utilities Index was measured using Mark III transforms—unadjusted scores (see Fig. 1A).
†
Statistically significant differences among children undergoing cochlear implantation at <18 months, 18 to 36 months, and >36 months of age (
P
< 0.05).
‡
Although household income was not significantly different among implant age groups using the six aforementioned family income categories, grouping by family income of less than $50,000
results in significantly lower frequencies among families of children implanted at younger ages (
p
= 0.012).
**Cognitive status measured by the Bayley Physical Developmental Index for children under 24 months of age and by Leiter Brief Intelligent Quotient Composite Score for children 24 months
of age or older.
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