Increased vulnerability of COPD patient groups to urban climate in view of global warming

Figures & data

Figure 1 Study cohorts.

Table 1 Comparison of patient characteristics and climate variables by season in the year 2012

Parameter	Spring	Summer	Autumn	Winter	Total	P-value
Admissions, n	120	90	109	108	427	-
Male, n (%)	61 (50.8%)	54 (60%)	72 (66.1%)	66 (61.1%)	253 (59.3%)	0.123
Female, n (%)	59 (49.2%)	36 (40%)	37 (33.9%)	42 (38.9%)	174 (40.7%)	0.123
Age, years, mean ± SD	72.8± 11.1	69.3± 11.5	70.9±9.9	72.7±12	71.4± 11.4	0.018*
BMI, kg/m^2, mean ± SD	27.6±8	25.9±6.9	27.0±8.3	24.6±6.5	26.4±7.6	0.050*
Smoker, n (%)	37 (39.8%)	34 (44.7%)	40 (47.1%)	38 (46.3%)	149 (44.3%)	0.960
Former smoker, n (%)	52 (55.9%)	38 (50%)	41 (48.2%)	41 (50%)	172 (51.2%)	0.960
Non-smoker, n (%)	4 (4.3%)	4 (5.3%)	4 (4.7%)	3 (3.7%)	15 (4.5%)	0.960
Pack years, mean ± SD	43.4±27.4	43.3±23	46.9±28.2	42.2±28.5	44.1 ±26.8	0.633
FEV1, %, mean ± SD	36.6± 15.8	37.4±19.7	37.1 ± 15.6	37.2±16.3	39.5±16.9	0.937
GOLD I or II, n (%)	22 (20.8%)	17 (20.3%)	20 (20%)	16 (16.3%)	75 (19.3%)	0.889
GOLD III, n (%)	38 (35.8%)	24 (28.6%)	33 (33%)	36 (36.7%)	131 (33.8%)	0.889
GOLD IV, n (%)	46 (43.4%)	43 (51.2%)	47 (47%)	46 (46.9%)	182 (46.9%)	0.889
With LTOT, n (%)	40 (71.4%)	24 (63.2%)	40 (58.8%)	36 (69.2%)	140 (65.1%)	0.454
Without LTOT, n (%)	16 (28.6%)	14 (36.8%)	28 (41.2%)	16 (30.8%)	75 (34.9%)	0.454
Charlson Index, mean ± SD	3.1 ±1.8	2.9±2	2.9± 1.8	2.8±1.7	2.9± 1.8	0.285
Coronary heart disease, n (%)	31 (25.8%)	22 (24.4%)	25 (22.9%)	39 (36.1%)	117 (27.4%)	0.392
Length of stay, days, mean ± SD	11.0±7.8	10.0±6.5	11.5±8.7	10.3±8.1	10.7±7.8	0.587
Admissions/day, mean ± SD	1.3± 1.3	1.0±0.9	1.2±1.1	1.2± 1.1	1.2± 1.1	0.520
Tmean, °C, mean ± SD	11.3±5.5	18.5±3.4	10.4±5.1	0.7±5.6	10.2±8.0	<0.001***
Tmax, °C, mean ± SD	16.2±6.6	23.2±4.3	14.3±6.3	3.1 ±5.5	14.2±9.2	<0.001***
Tmin, °C, mean ± SD	6.2±4.8	13.8±2.9	6.6±4.4	−2.0±6.2	6.2±7.3	<0.001***
ΔT, °C, mean ± SD	10.0±4.0	9.4±3.0	7.6±3.4	5.1 ±2.3	8.1 ±3.7	<0.001***
Air pressure, hPa, mean ± SD	1,009.9±9.9	1,008.8±5.0	1,007.9±7.7	1,011.7± 11.8	1,009.6±9.1	0.155
Air humidity, %, mean ± SD	64.4± 11.4	69.4±10.3	78.9±9.8	82.9±8.7	73.9±12.5	<0.001***

Notes:

* P<0.05;

*** P<0.001.

Abbreviations:BMI, body mass index; GOLD, global initiative for COPD; LTOT, long term oxygen therapy; T, temperature; SD, standard deviation.

Figure 2 Differences in the age and BMI of patients with AECOPD in relation to the season.

Notes: Displayed are mean values at 95% confidence intervals. *P<0.05.

Table 2 Comparison of AECOPD patient characteristics between hot and cold summers

Parameter	Hot summers	Cold summers	P-value
Admissions, n	250	313	–
Male, n (%)	129 (51.6%)	158 (50.5%)	0.800
Female, n (%)	121 (48.4%)	155 (49.5%)	0.800
Age, years, mean ± SD	70±11	71 ± 11	0.530
BMI, kg/m^2, mean ± SD	25.3±6.6	25.6±6.4	0.611
Smoker, n (%)	82 (58.2%)	112 (47.1%)	0.016*
Former smoker, n (%)	47 (33.3%)	114 (47.9%)	0.016*
Non-smoker, n (%)	12 (8.5%)	12 (5.0%)	0.016*
Pack years, mean ± SD	51.1 ±32.6	48.8±26.3	0.858
FEV1, %, mean ± SD	39.7± 15.2	39.5± 15.0	0.852
GOLD I or II, n (%)	42 (24.4%)	54 (19.3%)	0.367
GOLD III, n (%)	80 (46.5%)	146 (52.1%)	0.367
GOLD IV, n (%)	50 (29.1%)	80 (28.6%)	0.367
With LTOT, n (%)	71 (82.6%)	125 (83.3%)	0.859
Without LTOT, n (%)	15 (17.4%)	25 (16.7%)	0.859
Charlson Index, mean ± SD	2.6± 1.8	3.1 ±2.0	0.002**
Length of stay, days, mean ± SD	8.3±5.1	8.3±6.0	0.353
Admissions/day, mean ± SD	1.4± 1.2	1.7± 1.3	0.006**
Tmean, °C, mean ± SD	20.3±4.3	18.6±3.0	<0.001***
Tmax, °C, mean ± SD	25.4±5.2	23.3±4.0	<0.001***
Tmin, °C, mean ± SD	14.9±3.5	14.0±2.5	0.003**
ΔT, °C, mean ± SD	10.5±3.4	9.3±3.1	<0.001***
Air pressure, hPa, mean ± SD	1,009.3±6.1	1,008.0±5.5	0.059
Air humidity, %, mean ± SD	62.8± 14.3	67.8± 10.9	<0.001***

Notes:

* P<0.05;

** P<0.01;

*** P<0.001.

Abbreviations:BMI, body mass index; OLD, global initiative for COPD; LTOT, long term oxygen therapy; T, temperature; SD, standard deviation.

Table 3 Comparison of AECOPD patient comorbidities between hot and cold summers

Comorbidity	Hot summers	Cold summers	P-value
Coronary heart disease	83 (33.2%)	100 (31.9%)	0.786
Myocardial infarction	45 (17.6%)	33 (10.5%)	0.014*
Congestive heart failure	62 (24.8%)	100 (31.9%)	0.075
Peripheral vascular disease	19 (7.6%)	45 (14.4%)	0.016*
Cerebrovascular disease	21 (8.4%)	39 (12.5%)	0.132
Dementia	11 (4.4%)	20 (6.4%)	0.355
Chronic pulmonary diseasea	250 (100%)	313 (100%)	–
Connective tissue disease	0 (0%)	0 (0%)	–
Ulcer disease	12 (4.8%)	13 (4.2%)	0.837
Renal disease	37 (14.8%)	65 (20.8%)	0.078
Liver disease	4 (1.6%)	12 (3.8%)	0.131
Diabetes	52 (20.8%)	85 (27.1%)	0.093
Hemiplegia	4 (1.6%)	6 (1.9%)	1.000
Any tumor	21 (8.4%)	53 (17.0%)	0.004**
Leukemia	2 (0.8%)	4 (1.3%)	0.698
Lymphoma	3 (1.2%)	1 (0.3%)	0.328
AIDS	0 (0%)	0 (0%)	-

Notes:

* P<0.05;

** P<0.01;

a Inclusion criterion.

Figure 3 Increase in hospital admissions per day in relation to the minimum outdoor temperature.

Notes: The number of hospital admissions per day due to AECOPD are displayed as diamond markings. The trajectories were calculated using a locally-weighted scatter plot smoothing method. A vertical line marks the threshold temperatures for increased hospital admissions during the summer as calculated by Poisson regression analysis.
Abbreviation: T_min, daily minimum outdoor temperature.

Figure 4 Temperature analysis on the days preceding an increase in hospital admissions.

Notes: The figures show the daily minimum outdoor temperatures 1 week before an increase in hospital admissions to three or more AECOPD patients per day. The left column displays the results for hot summers, the right column for cold summers. Red and blue dots represent the recorded minimum outdoor temperatures. The number of admissions per day are shown as black dots. All trajectories were calculated with a locally-weighted scatter plot smoothing method. The black trajectories illustrate the daily admissions due to AECOPD, the red and blue curves represent minimum outdoor temperatures.
Abbreviation: T_min, daily minimum temperature.