Table 1 presented demographic characteristics of CVD cases enrolled in the NRCMS in Fuyang between January 2015 and June 2017. Overall, this study included 47.10% males, 26.29% older adults aged 75 or more, and 51.24% admissions in cold seasons. A total of 445 216 hospital admissions for total CVDs, 16 4004 for ischaemic heart disease, 6 342 for heart rhythm disturbances, 12 064 for heart failure, 244 367 for ischaemic stroke, and 18 441 for hemorrhagic stroke were identified.
Table 1. Demographic characteristics of people enrolled in the NRCMS programmein rural population of Fuyang city between January 2015 and June 2017.
Variable
|
Number (%) of enrolled individuals
|
Cardiovascular disease
|
Ischaemic heart disease
|
Heart rhythm disturbances
|
Heart failure
|
Ischaemic stroke
|
Haemorrhagic stroke
|
Total
|
445 216
|
164 004
|
6 342
|
12 064
|
244 367
|
18 441
|
Sex
|
|
|
|
|
|
|
Male
|
209 693 (47.10)
|
70 026 (42.70)
|
2 928 (46.17)
|
5 848 (48.47)
|
12 0697 (49.39)
|
10 203 (55.33)
|
Female
|
231 257 (51.94)
|
92 503 (56.40)
|
3 317 (52.30)
|
6 113 (50.67)
|
121 458 (49.70)
|
7 877 (42.71)
|
Age
|
|
|
|
|
|
|
18-64
|
162 794 (36.57)
|
54 028 (32.94)
|
3 085 (48.64)
|
2 921 (24.21)
|
93 520 (38.27)
|
9 523 (51.64)
|
65-74
|
163 195 (36.66)
|
60 068 (36.63)
|
1 733 (27.33)
|
4 236 (35.11)
|
91 848 (37.59)
|
5 383 (29.19)
|
≥75
|
117 046 (26.29)
|
49 087 (29.93)
|
1 386 (21.85)
|
5 235 (43.39)
|
58 055 (23.76)
|
3 336 (18.09)
|
Seasons
|
|
|
|
|
|
|
Warm
|
217 100 (48.76)
|
77 319 (47.14)
|
3 262 (51.43)
|
5 856 (48.54)
|
122 570 (50.16)
|
8 093 (43.89)
|
Cold
|
228 116 (51.24)
|
86 683 (52.85)
|
3 080 (48.57)
|
6 208 (51.46)
|
121 797 (49.84)
|
10 348 (56.11)
|
NRCMS = New Rural Cooperative Medical Scheme.
Table 2 showed the daily hospital admissions for total and cause- specific CVDs, NO2 levels, and meteorological variables. Mean hospital admissions per day (standard deviation) were 488.2 (117.1) for total CVDs, 179.8 (45.6) for ischaemic heart disease, 7.0 (3.3) for heart rhythm disturbances, 13.2 (7.2) for heart failure, 267.9 (67.7) for ischaemic stroke, and 20.2 (6.4) for hemorrhagic stroke occurred over the study period, respectively. The annual mean value for NO2 concentrations was 36.3 (12.4) µg/m3.
Table 2
Summary statistics on daily hospital admissions for total and cause-specific major cardiovascular diseases, NO2 levels, and weather conditions in rural regions of Fuang city between January 2015 and June 2017.
variable | | Mean | SD | Min | 25% | 50% | 75% | Max | IQR |
PM2.5(µg/m3) | | 60.4 | 36.6 | 6.0 | 35.0 | 50.0 | 77.0 | 276.0 | 42.0 |
PM10(µg/m3) | | 88.4 | 47.1 | 15.0 | 55.0 | 78.0 | 110.0 | 379.0 | 55.0 |
NO2(µg/m3) | | 36.3 | 12.4 | 13.0 | 28.0 | 34.0 | 42.0 | 93.0 | 14.0 |
CO (µg/m3) | | 870.3 | 379.2 | 200.0 | 600.0 | 800.0 | 1 000.0 | 2 900.0 | 400.0 |
SO2(µg/m3) | | 21.5 | 13.7 | 5.0 | 14.0 | 19.0 | 25.0 | 237.0 | 11.0 |
O3(µg/m3) | | 83.2 | 39.8 | 8.0 | 56.0 | 77.0 | 105.0 | 226.0 | 49.0 |
Mean temperature (°C) | | 15.4 | 9.1 | -7.8 | 7.2 | 16.3 | 23.2 | 32.1 | 16.0 |
Relative humidity (%) | | 76.8 | 13.2 | 38.0 | 68.4 | 78.1 | 86.6 | 99.3 | 18.2 |
All cardiovascular diseases | | 488.2 | 117.1 | 105.0 | 410.0 | 473.0 | 561.0 | 918.0 | 151.0 |
Ischaemic heart disease | | 179.8 | 45.6 | 33.0 | 148.8 | 174.5 | 208.0 | 364.0 | 59.2 |
Heart rhythm disturbances | | 7.0 | 3.3 | 0.0 | 5.0 | 7.0 | 9.0 | 19.0 | 4.0 |
Heart failure | | 13.2 | 7.2 | 0.0 | 8.0 | 12.0 | 18.0 | 40.0 | 10.0 |
Ischaemic stroke | | 267.9 | 67.7 | 53.0 | 224.0 | 259.0 | 307.2 | 482.0 | 83.2 |
Haemorrhagic stroke | | 20.2 | 6.4 | 4.0 | 15.0 | 20.0 | 24.0 | 50.0 | 9.0 |
NO2: nitrogen dioxide; SD: standard deviation; Min: minimum; Max: maximum; IQR: interquartile range. |
The Spearman correlations between six air pollutants and meteorological factors were showed in Table S1. Daily NO2 levels exhibited positive correlations with PM2.5, PM10, CO, and SO2 (r = 0.40 ~ 0.53), but negative correlations with O3, humidity, and temperature (r=-0.12 ~ -0.23).
Figure 2 showed the relation between NO2 and hospital admissions for total and cause-specific CVDs at different lag days. Similar lag results were observed on the effects of NO2 on total CVDs, ischaemic heart disease, and ischaemic stroke. With per 10 µg/m3 increase in NO2 concentrations, the highest estimates in significant increments of the hospital admissions were found at lag0-2 day for total CVDs (RR: 1.019, 95%CI: 1.005 to 1.032), ischaemic heart disease (1.021, 1.006 to 1.036), and ischaemic stroke (1.021, 1.006 to 1.035), but not for heart rhythm disturbances (0.996, 0.963 to 1.030), heart failure (1.018, 0.994 to 1.042) and hemorrhagic stroke (0.986, 0.966 to 1.005). (Table S2).
Figure 3 showed the associations between NO2 levels at lag0-2 day and hospital admissions for total and cause-specific CVDs, stratified by gender, age, and seasons. The associations were stronger in older individuals than in young individuals for total CVDs, ischaemic heart disease, and ischaemic stroke, although associations were only marginally significant in some instances. The estimates were consistently higher in females than in males for total CVDs and ischaemic stroke, but lower in females than in males for ischaemic heart disease although the differences were not significant. We found that the relation was also stronger in cold seasons than in warm seasons for total CVDs, ischaemic heart disease, and ischaemic stroke (all P < 0.05).
Table 3 presented the results of two-pollutant models at lag0-2 day. The effects of NO2 were similar with those from single-pollutant models. Table 4 presented the ANs and AFs of all CVDs incidence attributable to NO2. The ANs were 29 012 (8 323 to 48 710) for cardiovascular disease, 11 996 (3 594 to 19 962) for ischaemic heart disease, 17 397 (5 218 to 28 946) for ischaemic stroke, with AFs of 6.52% (1.87–10.94%) for total CVDs, 7.31% (2.19–12.17%) for ischaemic heart disease, 7.12% (2.14–11.85%) for ischaemic stroke, respectively.
Table 3
RRs* and 95% CIs for the associations of daily hospital admissions for cause-specific cardiovascular disease with 10 µg/m3 increase (log0-2) concentrations of NO2 in rural regions of Fuyang city between January 2015 and June 2017 using two-pollutant models.
Variables | Cardiovascular disease | | Ischaemic heart disease | | Heart rhythm disturbances | | Heart failure | | Ischaemic stroke | | Haemorrhagic stroke |
| RR | LCI | UCI | RR | LCI | UCI | RR | LCI | UCI | RR | LCI | UCI | RR | LCI | UCI | RR | LCI | UCI |
NO2 + PM2.5 | 1.017 | 1.002 | 1.033 | | 1.019 | 1.002 | 1.037 | | 0.997 | 0.958 | 1.036 | | 1.021 | 0.993 | 1.051 | | 1.019 | 1.002 | 1.035 | | 0.996 | 0.973 | 1.019 |
NO2 + PM10 | 1.015 | 0.999 | 1.030 | | 1.016 | 0.998 | 1.033 | | 0.994 | 0.956 | 1.034 | | 1.015 | 0.986 | 1.044 | | 1.017 | 1.000 | 1.034 | | 0.991 | 0.968 | 1.014 |
NO2 + O3 | 1.018 | 1.004 | 1.032 | | 1.020 | 1.005 | 1.036 | | 0.997 | 0.963 | 1.032 | | 1.020 | 0.996 | 1.046 | | 1.019 | 1.005 | 1.034 | | 0.992 | 0.972 | 1.012 |
NO2 + SO2 | 1.025 | 1.011 | 1.039 | | 1.026 | 1.010 | 1.041 | | 1.003 | 0.969 | 1.039 | | 1.017 | 0.992 | 1.042 | | 1.028 | 1.013 | 1.043 | | 0.988 | 0.968 | 1.008 |
NO2 + CO | 1.018 | 1.002 | 1.035 | | 1.017 | 0.999 | 1.035 | | 1.009 | 0.969 | 1.051 | | 1.022 | 0.992 | 1.052 | | 1.021 | 1.003 | 1.039 | | 0.997 | 0.974 | 1.021 |
NO2: nitrogen dioxide; RR: relative risk; CI: confidence interval. |
*Adjusted for temperature, relative humidity, calendar time, day of week, and public holiday. |
Table 4. Attributable numbers and fractions of hospital admissions to NO2 at lag 0-2 day in rural regions of Fuyang city between January 2015 and June 2017.
Disease
|
Attributable number (95% CI)
|
Attributable fraction in % (95% CI)
|
Cardiovascular disease
|
29 012 (8 323 to 48 710)
|
6.52 (1.87 to 10.94)
|
Ischaemic heart disease
|
11 996 (3 594 to 19 962)
|
7.31 (2.19 to 12.17)
|
Heart rhythm disturbances
|
-102 (-940 to 640)
|
-1.61 (-14.83 to 10.09)
|
Heart failure
|
744 (-285 to 1 688)
|
6.17 (-2.36 to 13.99)
|
Ischaemic stroke
|
17 397 (5 218 to 28 946)
|
7.12 (2.14 to 11.85)
|
Haemorrhagic stroke
|
-1 003 (-2 449 to 343)
|
-5.44 (-13.28 to 1.86)
|
NO2: nitrogen dioxide.
In the subgroup analyses by gender, age and seasons, AN and AF estimates of total CVDs and ischaemic stroke attributable to NO2 at lag0-2 day in males were more than in females, while AN and AF estimates of ischaemic heart disease in males were lower than in females. In addition, for total CVDs, ischaemic heart disease, and ischaemic stroke, AN and AF estimates were higher in older adults than in younger adults, and in cold seasons than in warm seasons (Table S3, S4, and S5).
Table S6 presented the results of the sensitivity analyses. The relation between NO2 and hospital admissions for total CVDs remained unchanged with different df for polynomials function, calendar time, temperature, and relative humidity. The cases hospitalized in areas other than Anhui province were included and similar effect estimate was found (RR: 1.018, 95% CI: 1.004 to1.032).