Safety of Metformin in Patients with Chronic Obstructive Pulmonary Disease and Type 2 Diabetes Mellitus

Figures & data

Table 1.  Comparison of baseline characteristics in metformin and non-metformin groups

Characteristic	N^a	Metformin group (n = 51)	Non-metformin group (n = 79)	p-value
Age – years	130	70.5 ± 9.6	74.7 ± 9.6	0.016
Female sex – n (%)	130	18 (35)	29 (37)	0.511
Smoking history
Current smoker – n (%)	130	17 (35)	11 (14)	0.016
Pack-years	58	40 (30–60)	50 (32–65)	0.580
Inhaled corticosteroid use – n (%)	130	20 (39)	38 (48)	0.368
Other treatments for diabetes – n (%)
Insulin	130	6 (12)	22 (28)	0.031
Sulphonylurea	130	17 (33)	23 (29)	>0.99
Thiazolidinedione	130	3 (6)	0 (0)	0.070
Meglitinide	130	0 (0)	1 (1)	>0.99
Body weight^b – kg	61	83.3 (71.4–104.1)	67.3 (52.2–79.8)	0.003
Male subjects	39	87.7 (79.2–108.8)	73.4 (64.5–88.0)	0.016
Female subjects	22	70.0 (63.4–97.0)	50.0 (39.4–64.0)	0.014
Spirometry
FEV1 – liters	32	0.93 (0.54–1.25)	0.92 (0.63–1.31)	0.833
FEV1 –% predicted	27	36 (23–48)	28 (11–45)	0.456
FVC – liters	32	1.78 (1.33–3.16)	2.06 (1.50–2.37)	0.803
Arterial blood gases at presentation
pH	120	7.38 (7.33–7.43)	7.41 (7.33–7.44)	0.165
PO2 – kPa	120	8.60 (7.27–11.60)	8.71 (7.41–11.42)	0.703
PCO2 – kPa	120	6.33 (5.24–8.18)	5.94 (4.85–7.24)	0.194
Oxygen saturation –%	108	93 (90–96)	93 (91–97)	0.972
Hypoxia – n (%)	120	35 (75)	53 (73)	0.497
Respiratory failure – n (%)	120	20 (43)	25 (34)	0.234
Respiratory acidosis – n (%)	120	16 (34)	17 (23)	0.141
Blood results
Hematocrit	128	0.39 (0.36–0.44)	0.39 (0.36–0.44)	0.596
Creatinine – μmol/L	129	89 (75–114)	93 (79–144)	0.196
Estimated GFR – mL/min/1.73 m^2	129	65 (53–87)	62 (39–79)	0.117
C reactive protein – mg/L	106	26 (6–72)	44 (14–95)	0.164
Random blood glucose – mmol/L	47	9.5 (6.8–13.3)	10.1 (7.1–14.5)	0.991
Hemoglobin A1c –%	51	8.2 (7.5–10.6)	7.8 (6.4–9.1)	0.140
Hemoglobin A1c – mmol/mol	51	66 (58–92)	62 (46–76)	0.140
Charlson co-morbidity index	130	2 (2–3)	3 (2–4)	0.099
APACHE II score	130	13 (9–17)	13 (11–17)	0.621

Notes: ^aNumber of patients with data available. ^bHeight was recorded in too few patients to permit meaningful comparison of body mass index.

Figure 1. First plasma lactate concentration at hospital admission. The horizontal bar indicates the median plasma lactate concentration (p = 0.012 Mann–Whitney test).

Figure 2. Kaplan-Meier curves for all-cause mortality. Patients on metformin are represented by a dashed line; those not on metformin by a solid line (p = 0.011, log-rank test).

Table 2.  Multivariate Cox proportional hazards regression model for death

Variable	Hazard ratio^a (95% CI)	p-value
Metformin therapy (present vs absent)	0.380 (0.150–0.967)	0.042
Age (years)	1.037 (0.980–1.097)	0.207
Sex (female vs male)	0.614 (0.234–1.608)	0.320
Year of admission	0.908 (0.779–1.059)	0.908
Body weight (kg)	1.027 (1.002–1.052)	0.034
Hemoglobin A1c (%)	1.008 (0.790–1.286)	0.951
Charlson co-morbidity index	1.186 (0.950–1.479)	0.131
APACHE-II^b score	0.906 (0.804–1.021)	0.105

Notes: ^aFor continuous variables, the hazard ratio represents the risk associated with a 1-unit increase.

^bAcute Physiology and Chronic Health Evaluation-II score.