Table 3.

Relative odds (95% CI) of 2001–2004 hospital admissions occurring in 2003–2004 per interquartile range (2.66 μg/m³) decrease in NO_x: (a) main analysis, (b) main analysis accounting for spatial dependence at the borough level and (c) using congestion charging zone as an instrumental variable

Diagnostic group	(a) Main analysis				(b) Spatial dependence					(c) Instrumental variable analysis
	Unadjusted		Adjusted*		Unadjusted		Adjusted*			Unadjusted		Adjusted*
	OR	95% CI	OR	95% CI	OR	95% CI	OR	95% CI	ICC	OR	95% CI	OR	95% CI
Cardiovascular	0.98	0.96 to 0.99	0.99	0.98 to 1.01	1.00	0.98 to 1.02	1.00	0.98 to 1.02	0.35	0.95	0.91 to 0.99	0.98	0.93 to 1.02
IHD	1.01	0.99 to 1.03	1.01	0.99 to 1.04	0.99	0.96 to 1.02	0.99	0.96 to 1.02	0.28	0.95	0.88 to 1.02	0.95	0.88 to 1.03
Stroke	0.95	0.89 to 1.00	1.00	0.97 to 1.04	1.00	0.96 to 1.04	1.02	0.98 to 1.07	0.14	0.92	0.83 to 1.02	0.99	0.88 to 1.10
Heart failure	0.94	0.91 to 0.97	0.94	0.90 to 0.97	0.96	0.91 to 1.00	0.96	0.91 to 1.01	0.19	0.88	0.79 to 1.00	0.92	0.81 to 1.05
Respiratory	0.97	0.96 to 0.98	0.97	0.96 to 0.99	1.00	0.99 to 1.02	1.00	0.98 to 1.02	0.37	0.98	0.95 to 1.02	1.00	0.95 to 1.05
COPD	0.98	0.96 to 1.01	0.97	0.94 to 1.01	1.00	0.96 to 1.04	0.99	0.95 to 1.03	0.16	1.03	0.94 to 1.12	1.00	0.91 to 1.10
Asthma	0.97	0.94 to 1.00	1.02	0.98 to 1.05	0.99	0.95 to 1.04	1.00	0.96 to 1.05	0.23	0.84	0.75 to 0.93	0.92	0.82 to 1.04
Bronchiolitis	0.94	0.88 to 1.00	0.91	0.85 to 0.98	0.92	0.85 to 1.00	0.91	0.84 to 0.99	0.06	0.91	0.74 to 1.22	0.79	0.63 to 0.98

^*Adjusted for IMD in 2001, change in proportion of residents living in income deprivation between 2001 and 2005, change in population aged 65 years or older between 2001 and 2004,% non-white, % black (black Caribbean, black African, black other), % Asian (Indian, Pakistani, Bangladeshi, Asian other) and % Chinese residents.

COPD, chronic obstructive pulmonary disease; ICC, intraclass correlation; IHD, ischaemic heart disease; IMD, Index of Multiple Deprivation; NO_x, oxides of nitrogen.