Results from the Cox proportional hazard regression model on the risk of hospitalisation due to pneumonia
| Entire cohort | Subgroup analysis* | Propensity matched‡ | ||||
| HR (95% CI) | P value | HR (95% CI) | P value | HR (95% CI) | P value | |
| Extrafine particles ICS | 0.75 (0.63 to 0.89) | 0.002 | 0.54 (0.45 to 0.65) | <0.0001 | 0.72 (0.60 to 0.87) | 0.0006 |
| ICS exposure groups† | ||||||
| Low (<420 µg/day) | ref | – | ref | – | Ref | – |
| Moderate (420–986 µg/day) | 1.11 (1.03 to 1.21) | 0.01 | 1.07 (0.90 to 1.27) | 0.5 | 1.25 (1.06 to 1.48) | 0.008 |
| High (>986 µg/day) | 1.35 (1.25 to 1.47) | <0.0001 | 1.14 (0.96 to 1.34) | 0.1 | 1.25 (1.05 to 1.49) | 0.01 |
| Male | 1.16 (1.09 to 1.23) | <0.0001 | 1.32 (1.18 to 1.48) | <0.0001 | 1.22 (1.07 to 1.38) | 0.002 |
| Age group | ||||||
| <62 | ref | – | ref | – | ref | – |
| 62–69 | 1.39 (1.25 to 1.54) | <0.0001 | 1.35 (1.10 to 1.66) | 0.005 | 1.35 (1.10 to 1.65) | 0.003 |
| 70–77 | 1.90 (1.72 to 2.11) | <0.0001 | 1.56 (1.28 to 1.91) | <0.0001 | 1.97 (1.62 to 2.39) | <0.0001 |
| >77 | 2.96 (2.67 to 3.28) | <0.0001 | 2.37 (1.95 to 2.89) | <0.0001 | 2.81 (2.30 to 3.43) | <0.0001 |
| BMI class, kg/m2 | ||||||
| <18.5 | 1.30 (1.18 to 1.43) | <0.0001 | 1.23 (1.05 to 1.44) | 0.01 | 1.26 (1.03 to 1.54) | 0.03 |
| 18.5–24.9 | ref | – | ref | – | ref | – |
| 25–29.9 | 0.90 (0.83 to 0.97) | 0.006 | 0.96 (0.84 to 1.11) | 0.6 | 0.88 (0.76 to 1.03) | 0.1 |
| 30–34.9 | 0.87 (0.78 to 0.96) | 0.007 | 0.93 (0.77 to 1.13) | 0.4 | 0.81 (0.66 to 0.99) | 0.04 |
| ≥35 | 1.12 (0.97 to 1.26) | 0.1 | 1.05 (0.82 to 1.3) | 0.7 | 1.14 (0.90 to 1.45) | 0.29 |
| Gold stage according to FEV1(%), | ||||||
| ≥ 80 | ref | – | ref | – | ref | – |
| 79–50 | 1.26 (1.03 to 1.55) | 0.02 | 1.46 (0.94 to 2.27) | 0.1 | 1.38 (0.92 to 2.07) | 0.1 |
| 49–30 | 1.76 (1.44 to 2.15) | <0.0001 | 1.91 (1.2 to 3.0) | 0.004 | 1.87 (1.26 to 2.79) | 0.002 |
| <30 | 2.37 (1.93 to 2.91) | <0.0001 | 2.37 (1.52 to 3.7) | 0.0001 | 2.81 (1.87 to 4.23) | <0.0001 |
| Smoking status | ||||||
| Active | 1.12 (1.045 to 1.19) | 0.003 | 1.11 (0.98 to 1.26) | 0.1 | 0.88 (0.66 to 1.17) | 0.07 |
| Former | ref | – | ref | – | ref | – |
| Never | 0.91 (0.75 to 1.09) | 0.3 | 1.03 (0.75 to 1.42) | 0.8 | 1.15 (0.99 to 1.32) | 0.4 |
| No of OCS treaments | ||||||
| 0 | ref | – | ref | – | ref | – |
| 1 | 1.30 (1.18 to 1.44) | <0.0001 | 1.18 (0.98 to 1.42) | 0.09 | 1.31 (1.06 to 1.62) | 0.01 |
| ≥2 | 1.67 (1.56 to 1.78) | <0.0001 | 1.52 (1.34 to 1.72) | <0.0001 | 1.62 (1.40 to 1.87) | <0.0001 |
| Asthma | 1.03 (0.96 to 1.11) | 0.3 | 1.01 (0.89 to 1.16) | 0.9 | 1.05 (0.92 to 1.20) | 0.5 |
*This analysis was only caried out on patients receiving ICS spray treatment.
†ICS exposure groups (low, moderate and high) were made by dividing the population into three equally big groups based on the ICS budesonide equivalent dose.
‡Propensyty matching using a greed match algorithm with up to five controls per case. Matching was done on the following variables: age, sex, smoking status, FEV1, BMI, ICS group, OCS group and asthma diagnosis.
BMI, body mass index; FEV1, forced expiratory volume in the first second; ICS, inhaled corticosteroid; OCS, oral corticosteroid.