. 2017 Oct 9;7:12861. doi: 10.1038/s41598-017-13168-8

Table 1.

Studies included in the meta-analysis.

Case Control Studies
Study	Year	Incidence of RA (AD)	Incidence of RA (controls)	Odds Ratio	95% CI	Details of Study Population	NOS Total Score
Heyman et al.³²	1983	16/40 (40%)	29/80 (36%)	1.17¹	0.54–2.56	Cases: 12 males and 28 females, all Caucasian. Mean age 60.8 at time of study admission.	6/9 (medium)
						Controls: Matched for age, sex and race
						Study Location: Duke University Medical School, North Carolina, USA
French et al.²⁶	1985	?/78	?/76	0.62¹	0.29–1.29	Cases: 78 Caucasian males.	7/9 (medium)
						Controls: Matched for age, sex and race. Separate neighbourhood and hospital control groups.
						Study Location: Veterans Administration Medical Centre, Minnesota, USA
Jenkinson et al.²⁷	1989	2/96 (2%)	12/92 (13%)	0.14	0.03–0.65*	192 inpatients of a geriatric unit. All 65 years or older.	5/9 (low)
Jenkinson et al.²⁷	1989	2/96 (2%)	12/92 (13%)	0.14	0.03–0.65*	Study Location: Hackney Hospital, London, UK	5/9 (low)
Graves et al.³¹	1990	8/130 (6.2%)	5/130 (3.8%)	1.18	0.35–3.91	Cases: 130 patients from a geriatric and family clinic	6/9 (medium)
						Controls: Matched where possible for age, sex, education, socioeconomic and marital status.
						Study Location: Washington, USA
Broe et al.²⁴	1990	92/170 (54%)	115/170 (68%)	0.56¹	0.36–0.87	Cases: Clinically diagnosed AD patients aged 52–96 years from a dementia clinic	7/9 (medium)
						Controls: Matched for age and sex
						Study Location: Sydney, Australia
Li et al.²⁸	1992	4/70 (5.7%)	35/140 (25%)	0.16¹	0.05–0.51	Cases: Clinically diagnosed AD patients from psychiatric hospitals and neurology clinics	6/9 (medium)
						Controls: Age and sex matched neighbourhood controls.
						Study Location: Beijing, China
Can. Health²⁵	1994	104/201 (52%)	280/468 (60%)	0.54¹	0.36–0.81	Cases: AD subjects age 65 + from both institutions and the community	7/9 (medium)
						Controls: Neighbourhood controls
						Study location: 36 cities across Canada
Brietner et al.²³	1994	7/50 (14%)	11/50 (22%)	0.64¹	0.22–1.77	Co-twin control study on twins with AD onset separated by 3 or more years. Subjects found using the US National Academy of Sciences Research Council Registry	5/9 (low)
Brietner et al.²³	1994	7/50 (14%)	11/50 (22%)	0.64¹	0.22–1.77	Study Location: USA	5/9 (low)
Population-based Studies
Study	Year	Incidence of RA in AD patients	Incidence of RA in controls	Odds Ratio	95% CI	Details of Study Population	NOS Total Score
Tyas et al.³⁰	2001	19/35(54%)	360/651 (55%)	0.81¹	0.39–1.68	Longitudinal study based on randomly selected subjects of 65 or older who were initially cognitively intact.	9/9 (high)
Tyas et al.³⁰	2001	19/35(54%)	360/651 (55%)	0.81¹	0.39–1.68	Study Location: Manitoba: Canada	9/9 (high)
Lindsay et al.²⁹	2002	90/167 (54%)	2013/3452 (58%)	0.61¹	0.43–0.87	Longitudinal study based on randomly selected subjects 65 or older from all 10 Canadian provinces	9/9 (high)
Lindsay et al.²⁹	2002	90/167 (54%)	2013/3452 (58%)	0.61¹	0.43–0.87	Study Location: Nationwide across Canada	9/9 (high)

The study characteristics of the 8 case control and 2 population-based studies included in the meta-analysis. 95% confidence intervals (CIs) and brief descriptions of the study populations, as well as the total NOS scale scores are included.

*Calculated based on raw data. Data was assumed to be unadjusted.

¹Study investigated ‘arthritis’ with no subtype for RA specifically.