Table 4.

Modifications of the effect of ambient PM_2.5 concentrations on heart failure admissions

	Description	n	% incr. risk#	LCLM^	UCLM^	p-value!
Individual-level risk factors
Age	85+	39,538	6.47	3.98	9.02	0.03
	75-84	53,248	3.78	1.35	6.27	0.51
	65-74	36,690	2.52	-0.84	6.00	0.89
	35-64	41,026	2.76	0.36	5.22	(ref)
Gender	female	75,670	4.57	2.15	7.05	0.18
	male	94,832	3.02	1.15	4.93	(ref)
Atherosclerosis (ICD = 440)	present	1,389	10.66	-1.79	24.69	0.29
	absent	169,113	3.83	2.41	5.26	(ref)
Previous heart failure admission (ICD = 428)	present	62,043	4.51	2.03	7.05	0.41
	absent	108,459	3.52	1.88	5.20	(ref)
Ischemic heart disease (ICD = 410-414)	present	86,599	3.92	1.54	6.36	0.95
	absent	83,903	3.85	2.05	5.69	(ref)
Conduction disorder (ICD = 426)	present	6,238	3.66	-2.29	9.96	0.94
	absent	164,264	3.89	2.46	5.34	(ref)
Diabetes (ICD = 250)	present	70,986	3.72	1.31	6.18	0.80
	absent	99,516	4.01	2.31	5.72	(ref)
COPD (ICD = 490-496)	present	51,736	2.48	-0.05	5.07	0.10
	absent	118,766	4.51	2.91	6.14	(ref)
Area-level risk factors
% adults living below poverty level, by census tract	20%-100%	57,593	2.45	-0.38	5.36	0.10
	7-20%	58,092	4.51	1.62	7.49	0.85
	0-7%	54,817	4.79	2.61	7.01	(ref)
Temporal variables
Season	Cool	94,252	4.10	1.49	6.78	0.74
	Warm	76,250	3.66	1.75	5.61	(ref)
Year*	2005	34,141	2.9	-0.10	6.05	0.23
	2001	34,363	4.9	2.73	7.10	(ref)

# percent change in risk of heart failure admission per 10 ug/m³ PM_2.5 averaged over lags 0-2

*modeled as continuous variable

^ lower and upper 95% confidence limit around risk estimate

! p-value for significance of interaction term