Table 1.
Basic information and characteristics of included studies
| Author/year | Country (ies) |
Geographic region (if in UK) | Type of study | Total sample size | % female | Mean age (years) | Comorbidities (where studied in the cohort) | Average duration of rheumatoid arthritis (months/years, as specified) |
| Alarcón32 2014 | Chile | . | Cross-sectional | 189 | 90.5 | 54.3 | . | . |
| Andersson19 2013 | Sweden | . | Cohort | 1460 | 68 | 54.2 | . | 6.7 months |
| Baldassari26 2014 | USA | . | Cross-sectional | 937 | 86.6 | 54.6 | Clinical Comorbidity Index based on 23 doctor-diagnosed conditions | 111 months (within eRA 6.6) |
| Barton27 2011 | USA | . | Cross-sectional | 498 | 84 | 54 | . | 10 years |
| Berkanovic28 1996 | USA | . | Cross-sectional | 118 | 75 | 51.7 | Mean no of comorbidities 1.05, range 0–5 | . |
| Brekke20 1999 | Norway | . | Cross-sectional | 247 (respondents); 133 assessed in clinic | 78.7 in respondents; 82.4 in clinic sample | 63.2 in respondents; 67.8 in clinic sample | Mean 1.1 in respondents | 12.7 months in respondents; 14.5 months in clinic sample |
| Callhoff21 2017 | Germany | . | Cross-sectional | 1492 | 81.6 | 54.9 | . | 14 years |
| Camacho15 2012 | UK | . | Cohort (Norfolk Arthritis Register; NOAR) | 553 | 62.8 | 57.2 | . | 5 months |
| Chandrashekara36 2018 | India | . | Cross-sectional | 1990 | 83.3 | 48.65 | Recorded as either present or absent: bronchial asthma, chronic heart failure, diabetes mellitus, hypertension, hypercholesterolaemia and thyroid illness. Occurrence of any one of the comorbidities was classified as ‘presence of comorbidity’ | . |
| Glave-Testino33 1994 | Mexico | . | Case–control | 128 | . | 45 | Patients with severe comorbidty excluded. Defined as: systemic arterial HTN, chronic renal failure, CHF, chronic liver disease, DM | 12 years |
| Gamboa-Cárdenas34 2019 | Peru | . | Cohort | 498 | 85.1 | 45.9 | . | 5.3 months (symptom duration) |
| Gong37 2016 | China | . | Cross-sectional | 207 | 85.5 | 49 | Persons with cognitive impairment or current severe diseases, such as cancer and stroke, were excluded. About one quarter of the participants (24.6%) had at least one comorbid disease, such as hypertension (5.8%), digestive system disorders (3.9%), heart disease (2.4%) and anaemia (1.9%). | 9.3 years |
| Hallert22 2015 | Sweden | . | Cohort | Cohort 1 (1996–98): 317; Cohort 2 (2006–9) 436 | 67%; 68% | 56; 58 | . | . |
| Harrison16 2009 | UK | . | Cohort (NOAR) | 1393 | 67 | 55 | . | 5 months |
| Harrison1 2005 | UK | Stoke on Trent; Cannock Chase; Truro; King’s College Hospital, London; and Macclesfield | RCT | 466 | 68 | 62.1 | Comorbidity information collected at baseline. Conditions grouped according to body system: cardiovascular disease including hypertension, psychiatric including depression, respiratory, endocrine, gastrointestinal, nervous system. | 11 years |
| Jacobi4 2003 | The Netherlands | . | Cohort | 869 | 71 | 59.5 | . | 8.7 years |
| Jiang40 2015 | Sweden | . | Cohort | 3021 | 72 | 54.5 | . | 6.5 months |
| Kearsley-Fleet17 2018 | UK | BSRBR-RA | Cohort | 13 502 | 76 | 57 | Categorised as 1, 2, 3+ | 10 years |
| Linde23 2009 | Denmark | . | Cohort | 3156 | 75 | 64.5 | Categorised as 1, 2, 3+ | 7.5 months |
| Massardo35 2012 | Chile | . | Cohort | 1093; 1059 when excluding those with missing ethnic data | 85.5 | 45.6 | . | 6 months |
| McEntegart2 1997 | UK | Scotland (divided whole and west), England, Wales | Cohort | 440 in 1980s cohort; 374 in 1993 cohort | . | 57.5 | . | . |
| Molina29 2015 | USA | . | Cohort | 1209 | 75.8 | 58 | . | 10.7 months (average of the three SES categories) |
| Moufarrej30 2015 | USA | . | Cross-sectional | 182 | 76.3 | 45.6 (DAS28≤3.2); 48.5 (DAS28>/=3.2) | . | . |
| Putrik39 2016 | Multinational | Multinational cohort | Cohort | 3920 | 82 | 56 | RDCI based on: ischaemic cardiovascular disease (myocardial infarction, stroke), cancer (colon, skin, lung, breast and uterus for women, prostate for men and lymphoma), gastrointestinal diseases (diverticulitis, ulcers), infections (hepatitis), lung disease (chronic obstructive pulmonary disease and asthma) and psychiatric disorders (depression) | . |
| Roodenrijs24 2020 | The Netherlands | . | Cohort | 152 (52 D2T) | 72.5 | 60.2 D2T; 64.5 non-D2T | EULAR comorbidity domains and Charlson Comorbidity Index | 17 years D2T; 14 years non-D2T |
| Vliet Vlieland25 1994 | The Netherlands | . | Cohort/ cross-sectional | 127 | 100 | 35.9 (disease onset) | . | 1.5 year (at diagnosis) |
| Yang31 2015 | Canada | . | Cohort | 2023 | 73 | 52.86 | . | 6.1 months |
| Yates18 2021 | UK | NEIAA | Cohort | 7455 | 62.3 | 56.7 | 40.2% ≥1 comorbidity | . |
| Young3 2000 | UK | Multiple | Cohort | 869 | 65.1 | 56 (median) | . | 6 months (median) |
| Zou38 2020 | Singapore | . | Cohort | 213 | 73.2 | 51.3 | Charlson Comorbidity Index, mean 1.1 | 1.8 months |
CHF, Congestive Heart Failure; DAS, Disease Activity Score; DM, Diabetes Mellitus; EULAR, European Alliance of Associations for Rheumatology; HTN, Hypertension; RCT, Randomised Controlled Trial; RDCI, Rheumatic Disease Comorbidity Index; SES, Socioeconomic Status.