Association Between Chronic Obstructive Pulmonary Disease and Type 2 Diabetes: A Systematic Review and Meta-Analysis

Figures & data

Figure 1. Study flow chart

Table 1. Full eligibility criteria used in the search strategy.

	Inclusion	Exclusion
Study design	Original studies: RCTs, case–control, cohort, and cross-sectional with quantitative outcomes	Editorials, comments, qualitative studies, annual reports, systematic reviews
Species	Only human	Study with other than humans (e.g. animals)
Reporting results	Odds ratio (OD) or relative risk (RR) or hazard ratio (HR) with 95% confidence intervals (CIs)	Other than odds ratio (OR) or relative risk (RR) or hazard ratio (HR)
Diagnoses	Hospital-diagnosed or self-reported physician diagnoses	Any other than hospital-diagnosed or self-reported physician diagnoses
Language	English, Danish, Norwegian, Swedish	Languages other than English, Danish, Norwegian, Swedish
Text	Abstract & full-text available	Abstract & full-text not available

Table 2. Characteristics of the studies included in the meta-analysis.

					Mean age (% T2D)		Mean BMI
Study	Country	Study-design	Ascertainment of COPD	Ascertainment of T2D	COPD	Non-COPD	COPD	Non-COPD	Gender	Quality assessment
Feary et al. ^37 (2010)	United Kingdom	Case-control study	BTS guidelines for the management of COPD	Information not given	N/A (12.2)	N/A (6.4)	N/A	N/A	49% women	7
Meteran et al. ^20 (2015)	Denmark	Twin-studies / Case-control study	Hospital discharge data on diagnosed COPD	Hospital discharge data on diagnosed T2D	Mean age of the population =59 (6.6) (2.3)		Mean BMI =25.3		53% women	7
Lee et al. ^28 (2013)	Taiwan	Prospective cohort study	Diagnosed with ICD codes	Diagnosed with ICD codes	67.9 (N/A)	67.9 (N/A)	N/A	N/A	28% women	9
Joo et al. ^38 (2012)	Korea	Case-control study	ATS/ERS guidelines	Glucose lowering medication or fasting blood glucose >126 mg/dl	54.4 (16.6)	64.4 (11.5)	N/A	N/A	All male	8
Lindberg et al. ^29 (2011)	Sweden	Retrospective cohort study	GOLD standard	Information not given	64.8 (10.0)	64.3 (11.3)	26.1	26.6	45% women	8
Rana et al. ^30 (2004)	United States	Retrospective cohort study	Questionnaire-based definition of COPD & test performed to confirm diagnosis	Questionnaire-based definition of T2D or symptoms combined with fasting glucose >140 mg/dl or random glucose >200 mg/dl	58.0 (N/A)	54.0 (N/A)	24.1	24.4	All women	8
Song et al. ^31 (2010)	United States	Prospective cohort study	Questionnaire-based definition of COPD	Questionnaire-based definition of T2D	57.8 (N/A)	55.0 (N/A)	26.1	25.7	All women	7

Figure 2. Forest-plot showing the association between COPD and T2D. Generic inverse variance outcome analysis with random effect on outcome of all included studies with adjusted data.

Figure 3. Funnel plot of standard error by log odds ratio of all included studies in the meta-analysis.

Figure 4. Forest plot showing the association between COPD and T2D. Generic inverse variance outcome analysis with random effect on the outcome of subgroup analysis comparing studies using COPD diagnosis according to guidelines versus studies with COPD diagnosis based on questionnaire.

Figure 5. Forest plot showing the association between COPD and T2D. Generic inverse variance outcome analysis on studies using diagnostic methods according to guidelines for both COPD and T2D.