Association of chronic obstructive pulmonary disease with mild cognitive impairment and dementia risk: A systematic review and meta-analysis

Table 1 Baseline and clinical characteristics of included studies

No.	Ref.	Country or region	Study design	Groups investigated	Age	Diagnostic criteria	Assessment scales	Adjusted variables	MCI (%)	Dementia (%)	NOS quality score
1	Mermit Çilingir et al[17], 2020	Turkey	Case Control	COPD-E (n = 30); COPD-S (n = 54); Control (n = 37)	COPD-E-71.8 ± 12.3; COPD-S- 62 ± 10.2; Control-65.9 ± 12.8	GOLD	MMSE; RCS	NA	NA	NA	7
2	Xie et al[18], 2019	China	Prospective Cohort	COPD (n = 515); No COPD (n = 4220)	COPD-82.9 ± 9.7	GOLD	MMSE	Age, gender, marital status, education level, alcohol drinking, current exercise, BMI, baseline prevalence of HTN, DM, and stroke	18.8; 14.6	2.9; 1.6	8
3	Samareh Fekri et al[19], 2017	Iran	Case Control	COPD (n = 87); Control (n = 60)	COPD-60.4 ± 9.8; Control-58.1 ± 9.8	GOLD	MMSE	Age and sex	51.7; 36.6	NA	7
4	Gupta et al[20], 2013	India	Case Control	COPD-(n = 40); Control (n = 40)	COPD-57.2 ± 9.1; Control-56.9 ± 9.2	GOLD	MMSE	Age	NA	NA	5
5	Li et al[21], 2013	China	Case Control	Mild COPD-(n = 27); Severe COPD-(n = 35); Control (n = 27)	Mild COPD-70.4 ± 7.7; Severe COPD-68.2 ± 7.8; Control-66.2 ± 7.1	GOLD	MMSE	Age, sex, education level, BMI, smoking status, and CVD	NA	NA	6
6	Li et al[22], 2013	China	Case Control	Mild COPD-(n = 37); Severe COPD-(n = 48); Control (n = 37)	Mild COPD-69.2 ± 8.1; Severe COPD-67.6 ± 7.6; Control-66.5 ± 6.9	GOLD	MMSE	Age, sex, education level, BMI, smoking status, and CVD	NA	NA	8
7	Liao et al[23], 2015	Taiwan	Retrospective Cohort	COPD (n = 20492); No COPD (n = 40765)	COPD-68.2 ± 12.4; No COPD-67 ± 12.5	ICD-9CM	NA	Age and sex	NA	13.29.11	7
8	Martinez et al[24], 2014	Michigan	Cross-sectional	COPD (n = 1812); No COPD (n = 15723)	COPD-70.3 ± 9.0; No COPD-68.7 ± 9.9	GOLD	ADL	Baseline cognition	16.5; 12.4	3.9; 3.1	8
9	Dal Negro et al[25], 2015	Italy	Cross-sectional	COPD with LTOT (n = 73); COPD without LTOT (n = 73)	COPD with LTOT-70.9 ± 8.9; No COPD with LTOT-71.2 ± 9.1	GOLD	MMSEMRC; CAT	Age, gender, smoking history, BMI, dyspnoea score, ABG, and lung function	32.8	NA	6
10	Singh et al[26], 2013	United States	Cross-sectional	COPD (n = 288); No COPD (n = 1639)	MCI-82.7 ± 11.2; Normal Cognition-79.7 ± 12.5	Standard criteria	BDI; CDR	BDI-II Depression, history of stroke, APOEe4 genotype, DM, HTN, CAD, and BMI	14.6; 27.1	NA	7
11	Singh et al[3], 2014	United States	Cross-sectional	Total COPD (n = 1425); COPD (n = 171); No COPD (n = 1254)	COPD-80.8 ± 7.5; No COPD-79.1 ± 7.5	Standard criteria	BDI	BDI-II depression, history of stroke, APOEe4 genotype, smoking, DM, HTN, CAD, z-scores, and BMI	NA	NA	7
12	Lutsey et al[27], 2019	United States	Prospective Cohort	COPD (n = 2490); No COPD (n = 6108)	COPD-55.1 ± 5.8; No COPD-53.9 ± 5.7	GOLD	NA	Age, sex, education level, race, center, cigarette smoking and pack-years of smoking, physical activity, BMI, systolic BP, BP medication use, diabetes, HDL, LDL lipid-lowering medications, CAD, heart failure, stroke, apolipoprotein E genotype, and fibrinogen	NA	NA	6
13	Siraj et al[28], 2020	United Kingdom	Case Control	COPD (n = 64397); No COPD (n = 243420)	COPD-66.4 ± 10.9; No COPD-65.7 ± 11	Standard criteria	NA	Age, sex, GP, BMI, smoking status, modified CCI, CV disease, corticosteroid use, and socioeconomic class	NA	NA	7
14	Villeneuve et al[29], 2012	Canada	Case Control	Total COPD (n = 45); Control (n = 50)	COPD-68.4 ± 8.7; Control-67.4 ± 8.7	GOLD	MMSE; MoCA	Age and education	36.0; 12.0	NA	5
15	Yeh et al[30], 2018	Taiwan	Prospective Cohort	COPD (n = 10260); No COPD (n = 20513)	COPD-65.6 ± 11.8; No COPD-65.5 ± 11.9	GOLD	NA	Age, sex, each comorbidity, inhaled corticosteroid, and oral steroids	NA	11.1; 8.81	4
16	Ozge et al[31], 2006	Turkey	Prospective cohort	COPD (n = 54); Control (n = 24)	COPD-64.6 ± 8.5; Control-62.4 ± 8.4	GOLD	MMSE,BDS, CDR, IADL	Age and sex	NA	NA	6
17	Favalli et al[32], 2008	Turkey	Cross-sectional	COPD (n = 21); Control (n = 20)	COPD-74.6 ± 5.4; Control-73.7 ± 4.5	GOLD	MMSE; GDS	NA	NA	NA	5
18	Liao et al[10], 2015	Taiwan	Retrospective Cohort	COPD (n = 8640); No COPD (n = 17280)	COPD-68.7 ± 10.7; No COPD-68.7 ± 10.7	ICD-9CM	Self-administered questionnaire	Age and sex	NA	5.22; 7.06	6
19	Thakur et al[33], 2010	United States	Retrospective Cohort	COPD (n = 1202); Control (n = 302)	COPD-58.2 ± 6.2; Control-58.5 ± 6.2	ICD-9CM	MRC; BODE index; MMSE	Age, sex, race, educational attainment, and smoking history	5.5; 2.0	NA	7
20	Zhou et al[34], 2012	China	Case Control	COPD (n = 110); Control (n = 110)	COPD-80.9 ± 1.7; Control-80.8 ± 1.5	GOLD	CDR; MMSE	Age and education	NA	NA	6
21	Dodd et al[4], 2013	United Kingdom	Cross-sectional	COPD-E (n = 30); COPD-S (n = 50); Control (n = 30)	COPD-E-70 ± 11; COPD-S-69 ± 8; Control-65 ± 8	GOLD	MMSE	Age	NA	NA	7
22	Isoaho et al[35], 1996	Finland	Case Control	COPD (n = 81); Control (n = 245)	COPD-70.4 ± 4.8; Control-71.3 ± 5.9	GOLD	MMSE	Age and sex	17.0; 13.0	7.1; 3.2	6
23	Lima et al[36], 2007	Brazil	Cross-sectional	COPD (n = 30); Control (n = 34)	COPD-65 ± 8; Control-66 ± 8	GOLD	MMSE; DSM-IV	NA	NA	NA	5
24	Ozyemisci-Taskiran et al[37], 2015	Turkey	Cross-sectional	COPD-E (n = 133); COPD-S (n = 34); Control (n = 34)	COPD-E-69.3 ± 8.9; COPD-S-67.5 ± 8.9; Control-68.3 ± 8.8	GOLD	MMSE; HAD; BODE	Age and sex	22.6	NA	6
25	Salik et al[38], 2007	Turkey	Cross-sectional	COPD (n = 32); Control (n = 26)	COPD-66.7 ± 2.5; Control-65.7 ± 7.3	GOLD	MMSE; MCS	NA	NA	NA	5
26	Sarınç Ulaşlı et al[39], 2013	Turkey	Case Control	COPD (n = 112); Control (n = 44)	COPD-65 ± 7.6; Control-64 ± 9	GOLD	MMSE	Age and sex	NA	NA	5
27	Tomruk et al[40], 2015	Turkey	Cross-sectional	COPD (n = 35); Control (n = 36)	COPD-62.9 ± 6.3; Control-60.8 ± 6.2	GOLD	MMSE	Age	NA	NA	4

COPD: Chronic obstructive pulmonary disease; S: Stable; E: Exacerbation; GOLD: Global Initiative for Chronic Obstructive Lung Disease; CAT: COPD Assessment Test; MMSE: Mini-Mental State Examination; COPD: Chronic obstructive pulmonary disease; LTOT: Long-term oxygen treatment; HAD: Hospital Anxiety and Depression; BODE: (B) BMI, (O) the severity of airflow obstruction (FEV1), (D) severity of dyspnea (modified Medical Research Council Dyspnea Scale), (E) exercise capacity; ICD-9CM: International Classification of Diseases, Ninth Revision, Clinical Modification; BDI: Beck Depression Inventory; IADL: Instrumental activities of daily living scale; CDR: Clinical dementia rating; BMI: Body mass index; CVD: Cardiovascular Disease; GP: General practice; DM: Diabetes mellitus; ABG: Arterial blood gas; HTN: Hypertension; CAD: Coronary artery disease; HDL: High Density lipoprotein; LDL: Low density lipoprotein; NA: Not applied.