Disparities in rheumatoid arthritis outcomes for North American Indigenous populations

Figures & data

Table 1. Physician visits and treatment gaps using provincial administrative health records data from January 1990 to December 2010.

	INA (N = 1095)	Non-INA (N = 7000)	RR (p value)^1
Physician visits- prevalent RA
All physician visits	109.5 (104.9–114.1)	98.64 (97.21–100.1)	p < 0.0001
Non-specialist visits	86.7 (82.5–91.0)	67.2(66.1–68.3)	p < 0.0001
Rheumatology visits	6.9 (6.4–7.4)	8.2 (8.0–8.4)	p < 0.0001
Treatment pattern – incident RA	INA (N = 566)	Non-INA (N = 3593)
Corticosteroids – ever	76%	65%	1.2 (p < 0.0001)
DMARDs – ever Months to start^2 Duration of use (mean month)^2 Proportion of RA duration on drug^3	74% 8 (6.7–9.5) 21(22) 34%	65% 6.5 (6–7) 25(24) 41%	1.12 (p < 0.003) p < 0.03 p < 0.01 p < 0.0001
Biologics – ever Months to start^2 Duration of use (mean month)^2 Proportion of RA duration on drug^3	12% 48 (39–57) 17(16) 22%	14% 36 (33–38) 22(19) 32%	p = 0.09 NS p = 0.005 NS p = 0.01
Treatment gaps – ever	57%	37%	1.5 (p < 0.0001)

¹Comparisons between FN and non-FN are reported as rate ratios (RR) with 95% confidence intervals (CI).

²Only for incident RA starting drug, mean months (95%CL).

³Only for incident RA, mean proportion of disease duration on drug, time to intervention mean days (CI mean), adj = time to intervention adjusted for proportion of time on drug adjusted for modified Charlson comorbidity index.

Table 2. Physician visits and treatment for RA patients followed in the rheumatology clinic. Data are from patients with >1 year and <15 years of disease and serial visits prior to 2015. INA = Indigenous North Americans (Cree, Ojibway and Ojicree people), SD = standard deviation.

	INA (N = 150)	White (N = 154)	p
RA disease duration in years (SD)	8 ± 5	9 ± 4 vs years	ns
Female sex (%)	85	79	ns
Time to first DMARD (months), mean ± SD	19.2 ± 26.4	15.3 ± 35.0	ns
Number of DMARD courses, mean ± SD	4.9 ± 2.9	3.6 ± 2.3	<0.001
Months on DMARD, mean ± SD	65.9 ± 43.7	77.6 ± 48.7	0.03
Months off DMARD/Year of disease, mean ± SD	4.6 ± 3.0	3.5 ± 3.0	0.019
Proportion on biologic (ever)	35%	33%	ns
Time to first biologic (months), mean ± SD	57.0 ± 34.5	45.7 ± 44.8	ns
Intramuscular methylprednisolone use (ever)	71%	48%	<0.001
Visits per year	1.6 ± 0.7	1.9 ± 0.5	0.007
Visits missed per year	0.15 ± 0.33	0.04 ± 0.10	<0.001
Distance travelled to clinic (average kilometres)	408 km	73	<0.001

Figure 1. Mortality in Indigenous North Americans and non-Indigenous North Americans with or without rheumatoid arthritis in provincial administrative health records data from January 1990 to December 2010. a) Age and sex-adjusted mortality; b) age sex and mCCI-adjusted mortality; c) mortality rate ratio (MRR) for RA comparing Indigenous North Americans (INA) versus non-Indigenous North Americans (nonINA). d) Age at death for incident rheumatoid arthritis. e) Survival curve (for incident RA). RA = rheumatoid arthritis; mCCI = modified Charlson comorbidity index (modified for use with Manitoba administrative data); INA = Indigenous North Americans; nonINA = non-Indigenous North Americans. Black bars mortality rate ratio adjusted for age, sex and mCCI. Grey bars mortality rate adjusted for age and sex.

Table 3. Low socioeconomic state and both physical and mental comorbidity at RA onset contribute to excess mortality in RA in provincial administrative health records data from January 1990 to December 2010.   

Variable	Hazzard ratio	95% CI	P value
INA	1.3	0.8–2.1	0.26
Male sex	1.3	1.0–1.6	0.04
Age group (years) <18 19–28 29–38 39–48 49–58 59–68 >69	ref 1.7 2,2 3.3 7.8 16.8 52.6	ref 0.2–18.6 0.3–18.3 0.4–25.2 1.1–56.9 2.3–121.9 7.3–377.3	-0.67 0.47 0.24 0.04 0.005 <0.0001
Income quintile^1 Q1 Q2 Q3 Q4 Q5	1.8 1.3 1.4 1.2 ref	1.2–2.0 0.88–1.99 0.92–2.1 0.77–1.83 ref	0.004 0.18 0.11 0.43 -
Comorbidity onset^2 Physical ADG Mental ADG	1.64 1.56	1.29–2.08 1.19–2.04	0.001 0.004

¹ Income quintile based on dissemination area level average household income values from public-use census files and postal codes. Higher quintile represents higher income [9].

² ADG = Aggregated Diagnosis Groups® (mental ADG®, physical ADG ®) created using the John Hopkins ACG® Case-Mix System Version 8. The mADG and pADG have been previously used in the Manitoba Provincial Registry Database [12].

Concept dictionary and glossary for population based research http://umanitoba.ca/faculties/health_sciences/medicine/units/chs/departmental_units/mchp/resources/concept_dictionary.html

 Google Scholar

Martens PBJ, BurlandE PRior H, Burchill C, et al. Profile of metis health status and healthcare utilization in Manitoba: a population-based study. Winnipeg Manitoba: Centre for Health Policy; 2010.

 Google Scholar