Impact of Comorbid Conditions on Healthcare Expenditure and Work-related Outcomes in Patients With Rheumatoid Arthritis

Martin Vu; Natalie Carvalho; Philip M. Clarke; Rachelle Buchbinder; An Tran-Duy

doi:10.3899/jrheum.200231

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Table 1.

RA-related comorbidities as potential predictors of healthcare expenditure and work-related outcomes.

Condition	ICD-9-CM Codes
Asthma	493
Cancer	140–239
Chronic obstructive pulmonary disease	491, 492, 496
Depression	311
Diabetes	250
Disorders of the eye and adnexa	360–379
Disorders of lipid metabolism	272
Heart failure	428
Hypertension	401
Myocardial infarction	410, 412
Osteoporosis	733
Peptic ulcer	531, 532, 533, 534
Stroke	430, 431, 432, 433, 434, 436, 437, 438

ICD-9-CM: International Classification of Diseases, 9th revision, Clinical Modification; RA: rheumatoid arthritis.

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Table 2.

Descriptive statistics on the sociodemographic and comorbid conditions.^{^a}

	Unweighted	Weighted^{^b}
Sex
Female	3454 (69.6)	3.0 (64.9)
Male	1513 (30.4)	1.6 (35.1)
Age, yrs, mean (SD)	59.8 (14.5)	60.9 (15.2)
Age, yrs
18–24	53 (1.1)	0.059 (1.3)
25–34	212 (4.3)	0.17 (3.7)
35–44	462 (9.3)	0.40 (8.6)
45–54	1046 (21.1)	0.92 (19.8)
55–64	1305 (26.3)	1.2 (24.8)
> 64	1889 (38.0)	2.0 (41.9)
Region
Northeast	712 (14.3)	0.76 (16.3)
Midwest	948 (19.1)	0.98 (21.0)
South	2174 (43.8)	1.9 (41.8)
West	1133 (22.8)	0.97 (20.9)
Marital status
Married	2290 (46.1)	2.4 (50.5)
Unmarried	2677 (53.9)	2.3 (49.5)
Race/ethnicity
White	2259 (45.5)	3.1 (67.2)
Black	1330 (26.8)	0.68 (14.6)
Hispanic	535 (10.8)	0.28 (6.0)
Other	843 (17.0)	0.57 (12.3)
Family income level
Poor/negative	1312 (26.4)	0.86 (18.6)
Near poor	483 (9.7)	0.37 (8.0)
Low income	897 (18.1)	0.79 (16.9)
Middle income	1283 (25.8)	1.3 (28.9)
High income	992 (20.0)	1.3 (27.6)
Insurance coverage
Uninsured	551 (11.1)	0.42 (9.0)
Any private	2124 (42.8)	2.4 (51.7)
Public only	2292 (46.1)	1.8 (39.2)
Education
High school not completed	1621 (32.6)	1.2 (25.3)
High school completed	1883 (37.9)	1.8 (39.5)
Bachelor’s degree	415 (8.4)	0.49 (10.5)
Postgraduate	213 (4.3)	0.27 (5.9)
Other degree	835 (16.8)	0.88 (18.9)
Smoking status
Nonsmoker	3835 (77.2)	3.6 (77.0)
Smoker	1132 (22.8)	1.1 (23.0)
Comorbid conditions^{^c}
Hypertension	3166 (63.7)	2.9 (62.2)
Lipid metabolism disorders	2316 (46.6)	2.2 (47.3)
Diabetes	1379 (27.8)	1.2 (25.1)
Depression	1009 (20.3)	0.93 (20.0)
Eye and adnexa disorders	837 (16.8)	0.84 (18.1)
Asthma	827 (16.6)	0.69 (14.8)
COPD	654 (13.2)	0.62 (13.3)
Cancer	595 (12.0)	0.68 (14.7)
Myocardial infarction	402 (8.1)	0.41 (8.8)
Osteoporosis	346 (7.0)	0.34 (7.3)
Stroke	298 (6.0)	0.29 (6.2)
Heart failure	156 (3.1)	0.14 (3.0)
Peptic ulcer	67 (1.3)	0.056 (1.2)
No comorbid conditions	724 (14.6)	0.68 (14.6)
Number of comorbid conditions, mean (SD)	2.4 (1.7)	2.4 (1.8)
Year
2006–2007	416 (8.4)	0.42 (9.1)
2008–2009	1086 (21.9)	1.0 (22.3)
2010–2011	1096 (22.1)	1.0 (22.5)
2012–2013	1200 (24.2)	1.1 (23.1)
2014–2015	1169 (23.5)	1.1 (22.9)

Values are expressed as n (%) unless otherwise indicated.
↵^a The sample patient population was 4967, representing approximately 4.68 million US adult RA patients.
↵^b Number of patients are in millions.
↵^c Comorbidities were selected based on a prevalence of > 1%.
COPD: chronic obstructive pulmonary disease; RA: rheumatoid arthritis.

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Table 3.

Multivariable GLM results for total annual healthcare expenditure in patients with RA.

	Mean Ratio, (95% CI)^{^a}	Mean Difference, 2015 US$ (95% CI)^{^b}
Hypertension	1.23 (1.06–1.43)^*	2343 (605–4079)^*
Lipid metabolism disorders	0.95 (0.83–1.09)	535 (−1993 to 923)
Diabetes	1.24 (1.08–1.43)^*	2603 (813–4393)^*
Depression	1.40 (1.21–1.61)^**	4235 (2167–6301)^**
Eye and adnexa disorders	1.22 (1.05–1.42)^*	2407 (440–4373)^*
Asthma	1.09 (0.92–1.28)	968 (−961 to 2896)
COPD	1.46 (1.26–1.69)^**	4972 (2633–7311)^**
Cancer	1.32 (1.13–1.53)^**	3372 (1322–5423)^*
Myocardial infarction	1.60 (1.27–2.01)^**	6511 (2699–10,323)^*
Osteoporosis	1.27 (1.05–1.53)^*	2925 (318–5531)^*
Stroke	1.47 (1.19–1.82)^**	5150 (1764–8536)^*
Heart failure	1.75 (1.38–2.22)^**	8205 (3683–12,726)^**
Sex (ref: male)
Female	1.13 (0.99–1.30)
Age	1.00 (0.99–1.01)
Region (ref: West)
Northeast	1.19 (0.97–1.46)
Midwest	1.26 (1.03–1.55)^*
South	1.06 (0.90–1.25)
Insurance coverage (ref: public only)
Any private	0.97 (0.84–1.13)
No insurance	0.52 (0.43–0.62)^**
Education (ref: high school not completed)
High school completed	1.07 (0.93–1.24)
Bachelor degree	1.56 (1.21–2.01)^*
Postgraduate degree	1.36 (0.98–1.89)
Other degree	1.33 (1.12–1.59)^*
Smoking status (ref: nonsmoker)
Smoker	0.80 (0.67–0.95)^*

↵^a Values are the exponential form of the β coefficients for a covariate, which represents the multiplier factor for the outcome when the covariate increases by 1; the reference for each comorbidity is absence of the condition.
↵^b Values are the average marginal effect for a comorbidity compared to absence of the condition, holding all other covariates at the average values.
↵^* P < 0.05.
↵^** P < 0.001.
COPD: chronic obstructive pulmonary disease; GLM: generalized linear model; RA: rheumatoid arthritis.

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Table 4.

Multivariable logistic regression results for employment status in patients of working age (18–64 yrs) with RA.

	OR (95% CI)^{^a}
Hypertension	0.69 (0.51–0.92)^*
Lipid metabolism disorders	1.01 (0.78–1.32)
Diabetes	0.85 (0.61–1.18)
Depression	0.47 (0.34–0.63)^**
Eye and adnexa disorders	0.83 (0.54–1.27)
Asthma	1.06 (0.72–1.54)
COPD	0.53 (0.35–0.82)^*
Cancer	0.46 (0.27–0.79)^*
Myocardial infarction	0.60 (0.36–1.01)
Osteoporosis	0.55 (0.30–0.99)^*
Stroke	0.48 (0.26–0.89)^*
Heart failure	0.08 (0.02–0.29)^**
Peptic ulcer	0.74 (0.19–2.78)
Sex (ref: male)
Female	0.70 (0.52–0.95)^*
Age	0.98 (0.96–0.99)^*
Marital status (ref: unmarried)
Married	0.78 (0.59–1.04)
Race/ethnicity (ref: White)
Black	0.86 (0.63–1.17)
Hispanic	1.27 (0.87–1.87)
Other	0.89 (0.62–1.29)
Insurance coverage (ref: public only)
Any private	10.35 (7.35–14.57)^**
No insurance	3.43 (2.30–5.123
Education (ref: high school not completed)
High school completed	1.43 (1.01–2.03)^*
Bachelor degree	2.46 (1.37–4.42)^*
Postgraduate degree	2.56 (1.36–4.83)^*
Other degree	1.79 (1.20–2.67)^*
Smoking status (ref: nonsmoker)
Smoker	0.91 (0.66–1.26)

↵^a The OR is the exponential form of the β coefficient, which represents the multiplier factor for the odds of being employed when the covariate increases by 1; the reference for each comorbidity is the absence of the condition.
↵^* P < 0.05.
↵^** P < 0.001.
COPD: chronic obstructive pulmonary disease; RA: rheumatoid arthritis.

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Table 5.

Multivariable zero-inflated negative binomial regression results for absenteeism in employed patients of working age (18–64 yrs) with RA.

	Zero-inflation Component OR (95% CI)^{^a}	Count Component IRR (95% CI)^{^b}
Hypertension	0.38 (0.12–1.19)	1.30 (1.00–1.69)^*
Lipid metabolism disorders	0.42 (0.10-1.70)	0.83 (0.62–1.11)
Diabetes	2.96 (0.59–14.95)	1.08 (0.77–1.51)
Depression	1.14 (0.35–3.72)	1.44 (1.05–1.97)^*
Eye and adnexa disorders	0.25 (0.03–2.02)	1.51 (1.03–2.21)^*
Asthma	0.00 (0.00–0.00)	1.19 (0.86–1.64)
COPD	0.00 (0.00–0.00)	1.40 (0.92–2.15)
Cancer	0.86 (0.22–3.27)	1.39 (0.88–2.21)
Myocardial infarction	< 0.001 (< 0.001 to > 1,000)^{^c}	1.06 (0.58–1.93)
Osteoporosis	< 0.001 (< 0.001 to > 1,000)^{^c}	0.61 (0.35–1.08)
Stroke	1.93 (0.17–21.40)	2.15 (1.03–4.47)^*
Heart failure	< 0.001 (< 0.001 to > 1,000)^{^c}	0.86 (0.20–3.80)
Peptic ulcer	< 0.001 (< 0.001 to > 1,000)^{^c}	0.52 (0.10–2.73)
Sex (ref: male)
Female	1.01 (0.43–2.37)	1.11 (0.85–1.45)
Age	1.11 (1.04–1.19)^*	1.00 (0.99–1.01)
Region (ref: West)
Northeast	0.59 (0.16–2.21)	1.05 (0.71–1.55)
Midwest	0.81 (0.26–2.52)	1.40 (1.00–1.97)^*
South	0.65 (0.23–1.86)	1.25 (0.89–1.76)
Marital status (ref: unmarried)
Married	4.70 (1.40–15.73)^*	1.23 (0.97–1.56)
Race/ethnicity (ref: White)
Black	0.20 (0.02–1.84)	1.07 (0.77–1.49)
Hispanic	0.38 (0.11–1.28)	0.78 (0.53–1.16)
Other	0.52 (0.17–1.64)	0.80 (0.57–1.13)
Income level (ref: poor/negative)
Near poor	0.12 (0.00–8.89)	1.12 (0.63–1.99)
Low income	0.20 (0.03–1.29)	0.92 (0.60–1.40)
Middle income	0.42 (0.10–1.83)	0.77 (0.51–1.18)
High income	0.38 (0.08–1.78)	0.63 (0.40–0.98)^*
Insurance coverage (ref: public only)
Any private	0.30 (0.06–1.41)	1.19 (0.82–1.71)
No insurance	2.42 (0.56–10.39)	0.88 (0.57–1.36)
Education (ref: high school not completed)
High school completed	1.57 (0.40–6.18)	0.93 (0.67–1.29)
Bachelor degree	0.68 (0.12–4.01)	0.71 (0.45–1.10)
Postgraduate degree	3.37 (0.43–26.66)	1.15 (0.65–2.04)
Other degree	1.30 (0.23–7.28)	1.16 (0.79–1.70)
Smoking status (ref: nonsmoker)
Smoker	< 0.001 (< 0.001 to > 1,000)^{^c}	0.85 (0.65–1.12)

↵^a The OR is the exponential form of the β coefficient, which represents the multiplier factor for the odds of having undetected sick leave when the covariate increases by 1; the reference for each comorbidity is absence of condition.
↵^b The IRR is the exponential form of the b coefficient, which represents the multiplier factor for the expected days of sick leave when the covariate increases by 1; the reference for each comorbidity is absence of condition.
↵^c Very small positive values of OR and lower limit of the 95% CI, and very large value of the upper limit of the 95% CI.
↵^* P < 0.05.
COPD: chronic obstructive pulmonary disease; IRR: incidence rate ratio; RA: rheumatoid arthritis.

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Table 6.

Multivariable GLM results for income in patients with RA.

	Mean Ratio, (95% CI)^{^a}	Mean Difference, 2015 US$ (95% CI)^{^b}
Diabetes	0.85 (0.75–0.96)^*	−5816 (−10,218 to -1415)^*
Asthma	1.03 (0.83–1.27)	1027 (−7615 to 9670)
COPD	0.71 (0.59–0.85)^**	−11,437 (−16,899 to -5977)^**
Heart failure	0.59 (0.36–0.97)^*	−15,833 (−27,231 to -4435)^*
Peptic ulcer	0.83 (0.49–1.39)	−6799 (−23,629 to 10,029)
Sex (male as reference)
Female	0.75 (0.67–0.84)^**
Marital status (ref: unmarried)
Married	1.01 (0.89–1.15)
Insurance coverage (ref: public only)
Any private	2.05 (1.70–2.47)^**
No insurance	1.11 (0.87–1.42)
Education (ref: high school not completed)
High school completed	1.07 (0.87–1.31)
Bachelor degree	1.82 (1.43–2.31)^**
Postgraduate degree	1.92 (1.46–2.53)^**
Other degree	1.36 (1.07–1.73)^*
Smoking status (ref: nonsmoker)
Smoker	0.92 (0.81–1.04)

↵^a Values are the exponential form of the β coefficients for a covariate, which represents the multiplier factor for the outcome in patients with the comorbid condition or certain level of a categorical variable compared to the reference; the reference for each comorbidity is absence of the condition.
↵^b Values are the average marginal effect for a comorbidity compared to absence of the condition, holding all other covariates at the average values.
↵^* P < 0.05.
↵^** P < 0.001.
COPD: chronic obstructive pulmonary disease; GLM: generalized linear model; RA: rheumatoid arthritis.