Prevalence of osteoarthritis among adults with cerebral palsy
Table I. Descriptive characteristics of adults with and without
cerebral palsy (CP)
Descriptive characteristics
Age, mean (SD)
18–30 years
31–40 years
41–50 years
51–60 years
61–70 years
> 70 years
Sex
Female
Male
Ethnicity
White
Black
Hispanic
Asian
Unknown/missing
Education
Less than high school
High school diploma
More than high school
Unknown/missing
Household annual income
< 40,000 US$
40–59,900 US$
60–99,900 US$
≥ 100,000 US$
Unknown/missing
With CP
(n = 7,348)
% (n ) Without CP
(n = 8,732,455)
% (n)
49.8
20.0
14.1
14.5
19.6
18.6
13.3 55.2
12.4
13.1
14.5
17.0
18.9
24.1
(18.2)
(1,467)
(1,034)
(1,066)
(1,437)
(1,364)
(980)
(18.6)
(1,083,125)
(1,141,701)
(1,264,473)
(1,486,496)
(1,648,551)
(2,108,109)
49.2 (3,615)
50.8 (3,733) 55.3 (4,826,637)
44.7 (3,905,818)
57.0 (4,190)
11.6 (855)
8.3 (607)
1.8 (130)
21.3 (1,566) 55.9 (4,882,512)
8.0 (698,549)
9.0 (781,721)
3.8 (334,945)
23.3 (2,034,728)
0.5 (35)
32.1 (2,358)
62.9 (4,618)
4.6 (337) 0.5 (47,275)
25.3 (2,209,051)
69.6 (6,074,054)
4.6 (402,075)
24.6
11.5
16.2
17.1
30.6 16.8
11.7
21.4
28.2
22.0
(1,810)
(845)
(1,191)
(1,253)
(2,249)
(1,462,452)
(1,019,787)
(1,865,676)
(2,463,266)
(1,921,274)
SD: standard deviation.
All analyses were performed using SAS version 9.4 (SAS
Institute, Cary, NC, USA). All assumptions for statistical tests
were met. p ≤ 0.005 (2-tailed) was used to determine statisti-
cal significance for this large sample, as recommended by a
coalition of methodologists to detect new discoveries (18, 19).
Effect estimates were reported as odds ratios (OR) with 99.5%
confidence intervals (95% CI).
RESULTS
Descriptive characteristics for adults with CP (n = 7,348)
and without CP (n = 8.7 million) are shown in Table I.
The proportion of adults aged 18–30 years was higher
for CP (20.0%, 12.4%), and the proportion of adults > 70
years of age was lower for CP (13.3%, 24.1%).
577
The prevalence of OA in adults with and without
CP, as well as the adjusted odds for each type of OA, is
shown in Table II. After adjusting for age and sex, and
compared with adults without CP, adults with CP had
higher odds of any OA, poly OA, hip OA, knee OA, and
other/unspecified OA (ORs 1.34–2.28; all p < 0.005), but
not hand OA (OR 0.86; 99.5% CI 0.48–1.54; p = 0.459).
The group by sex interaction was only significant for
hip OA (p < 0.005). After stratifying by sex, men with
CP had higher age-adjusted odds of hip OA compared
with men without CP (OR 2.47; 95% CI 1.87–3.27), and
women with CP had higher age-adjusted odds of hip OA
compared with women without CP (OR 1.72; 95% CI
1.29–2.30). Of the OA outcomes that were significantly
different between groups, the CP group by age group
interaction was significant for any OA, hip OA, knee
OA, and other/unspecified OA (all p < 0.005). After
stratifying by age group, the sex-adjusted odds were
higher for all age groups for any OA (ORs 1.72–4.09;
all p < 0.005), hip OA (ORs 1.54–10.93; all p < 0.005),
and other/unspecified OA (ORs 1.79–4.80; all p < 0.005),
and were higher for all age groups for knee OA (ORs
1.42–3.33; all p < 0.005) except for 61–70 year olds (OR
1.10; p = 0.277) or > 70 year olds (OR 0.99; p = 0.930).
The younger age groups tended to have higher odds
than the older age groups for CP (e.g. any OA: 18–30
years, OR 4.09; > 70 years, OR 1.72). Sensitivity ana-
lysis including individuals with complete data on all
covariates (n = 5,865,485) revealed that, for each of the
OA measures, the addition of ethnicity, education level,
and household annual income had little impact on the
main effect of CP group (Table II) and the conclusions
were the same as the primary analysis.
The unadjusted prevalence of any OA across age and
sex strata is shown in Fig. 1. There was an increasing
trend of any OA for men and women with and without
CP. The unadjusted OR for any OA was higher for
men and women across all age groups, and tended to
be higher for the younger age groups compared with
the older age groups (Table III).
Table II. Prevalence and adjusted odds of osteoarthritis (OA) among adults (≥ 18 years) with and without cerebral palsy (CP)
Any OA
Poly OA
Hip OA
Knee OA
Hand OA
Other/unspecified OA
With CP
(n = 7,348)
% (n) Without CP
(n = 8,732,455)
% (n)
20.3 (1,489)
3.9 (288)
2.8 (205)
6.0 (437)
0.3 (23)
13.0 (953) 15.1 (1,314,760)
2.5 (222,199)
1.9 (161,614)
5.8 (510,404)
0.5 (41,037)
8.5 (740,533)
Adjusted odds a (ref: without CP) Adjusted odds b (ref: without CP)
OR (99.5% CI)
OR (99.5% CI)
2.11 (1.93–2.30)
2.28 (1.92–2.71)
2.05
1.34
0.86
2.28
(1.68–2.51)
(1.16–1.54)
(0.48–1.54)
(2.06–2.53)
1.88
1.76
1.91
1.36
1.23
2.07
(1.68–2.11)
(1.38–2.24)
(1.46–2.49)
(1.14–1.63)
(0.64–2.35)
(1.81–2.36)
a
Adjusted for age and sex; n = 8,739,803.
Adjusted for age, sex, ethnicity, education level, and household annual income for participants with complete data; n = 5,865,485.
OR: odds ratio; CI: confidence interval.
b
J Rehabil Med 51, 2019