Table 2.
Association between quartiles of air pollution exposure (Q1–Q4) and mental health service use over 1-year and 7-year follow-upa
| Outcome and pollutant | 1-year follow-up | 7-year follow-up | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Complete case sample, n | Quartiles of air pollution exposure | Complete case sample, n | Quartiles of air pollution exposure | |||||||||
| Q1 (ref) | Q2, RR (95% CI) |
Q3, RR (95% CI) |
Q4, RR (95% CI) |
E-value, RR (lower CI) |
Q1 (ref) | Q2, RR (95% CI) |
Q3, RR (95% CI) |
Q4, RR (95% CI) |
E-value, RR (lower CI) |
|||
| In-patient days | 12 250 | 12.270 | ||||||||||
| NO2 | − | 1.32*** (1.16−1.51) | 1.21* (1.01−1.46) | 1.46*** (1.18−1.80) | 2.28 (1.64) | − | 1.49*** (1.30−1.70) | 1.27* (1.06−1.53) | 1.22 (0.99−1.51) | 1.74 (1.00) | ||
| NOx | − | 1.33*** (1.16−1.52) | 1.22* (1.00−1.47) | 1.45*** (1.17−1.81) | 2.26 (1.62) | − | 1.46*** (1.27−1.67) | 1.26* (1.04−1.51) | 1.17 (0.94−1.44) | 1.62 (1.00) | ||
| PM2.5 | − | 1.22* (1.01−1.47) | 1.32* (1.06−1.65) | 1.25 (0.97−1.60) | 1.81 (1.00) | − | 0.96 (0.80−1.16) | 0.97 (0.78−1.21) | 1.28* (1.00−1.63) | 1.88 (1.00) | ||
| PM10 | − | 1.06 (0.92−1.23) | 0.70*** (0.58−0.85) | 0.93 (0.75−1.14) | 1.36 (1.00) | − | 0.91 (0.79−1.05) | 0.77* (0.64−0.93) | 1.16 (0.94−1.43) | 1.59 (1.00) | ||
| CMHS events | 12 185 | 12 232 | ||||||||||
| NO2 | − | 1.16*** (1.10−1.23) | 1.32*** (1.23−1.42) | 1.48*** (1.36−1.62) | 2.32 (2.06) | − | 1.14*** (1.08−1.19) | 1.26*** 1.18−1.36) | 1.36*** (1.26−1.47) | 2.06 (1.83) | ||
| NOx | − | 1.17*** (1.11−1.23) | 1.32*** (1.22−1.42) | 1.49*** (1.37−1.63) | 2.34 (2.08) | − | 1.13*** (1.08−1.19) | 1.24*** (1.16−1.32) | 1.34*** (1.24−1.45) | 2.01 (1.79) | ||
| PM2.5 | − | 1.18*** (1.10−1.27) | 1.19*** (1.09−1.30) | 1.24*** (1.13−1.36) | 1.79 (1.51) | − | 1.12** (1.05−1.19) | 1.11** (1.03−1.19) | 1.15** (1.06−1.25) | 1.57 (1.31) | ||
| PM10 | − | 1.01 (0.95−1.07) | 1.02 (0.94−1.10) | 1.12* (1.03−1.22) | 1.49 (1.21) | − | 0.96 (0.91−1.01) | 1.04 (0.97−1.11) | 1.09* (1.01−1.17) | 1.40 (1.11) | ||
CMHS, community mental health services; E-value, association required between unmeasured confounder(s) and both the exposure and outcome to make Q4 effects non-significant, above and beyond measured covariates; NO2, nitrogen dioxide; NOx, nitrogen oxides; PM2.5, particulate matter <2.5 μm in diameter; PM10, particulate matter <10 μm in diameter; RR, relative risk.
The quartile cut-offs for NO2 were: Q1 <32.65 μg/m3, Q2 <39.41 μg/m3, Q3 <48.08 μg/m3 and Q4 ≥48.08 μg/m3; for NOx they were: Q1 <50.74 μg/m3, Q2 <66.83 μg/m3, Q3 <90.50 μg/m3 and Q4 ≥90.50 μg/m3; for PM2.5 they were: Q1 <12.64 μg/m3, Q2 <14.28 μg/m3, Q3 <15.36 μg/m3 and Q4 ≥15.36 μg/m3; and for PM10 they were: Q1 <18.81 μg/m3, Q2 <21.41 μg/m3, Q3 <24.50 μg/m3 and Q4 ≥24.50 μg/m3. All models were adjusted for seasonality, year, gender, ethnicity, age, marital status, population density, deprivation, ethnic density and social fragmentation. Analyses were conducted on those with complete covariate data.
P < 0.05, **P < 0.01, ***P < 0.001.