Table 5.

Second-stage random-effects meta-analysis and meta-regression models of 89 county-specific results: Wald test on significance of urbanization level in explaining variations in relative risks for heat (99th percentile vs. MMT) and for cold (1st percentile vs. MMT), and overall cumulative temperature–mortality curves, Cochran Q test for heterogeneity, $I^2$ statistics for residual heterogeneity.

Cause-specific mortality and subgroups	$I^2$ and Q test	RR for heat (99th vs. MMT)			RR for cold (1st vs. MMT)			Overall temperature–mortality associations
		Intercept only	Urbanization level	Wald test (p-value)	Intercept only	Urbanization level	Wald test (p-value)	Intercept only	Urbanization level	Wald test (p-value)
All cause	$I^2$ (%)	30.5	22.9	$<0.001$	20.1	15.4	$<0.001$	20.9	16.8	$<0.001$
	Q test (p-value)	$<0.001$	0.004		$<0.001$	0.014		$<0.001$	0.005
Nonaccidental	$I^2$ (%)	25.7	18.9	$<0.001$	20.9	16.7	$<0.001$	17.4	14.2	$<0.001$
	Q test (p-value)	$<0.001$	0.003		$<0.001$	0.008		0.004	0.018
Age 0–64	$I^2$ (%)	16.3	14.7	0.884	1.0	1.0	0.118	7.3	6.4	0.139
	Q test (p-value)	0.033	0.018		0.456	0.513		0.163	0.180
Age $65+$	$I^2$ (%)	23.8	17.3	$<0.001$	20.2	16.8	$<0.001$	18.6	15.8	$<0.001$
	Q test (p-value)	$<0.001$	0.007		$<0.001$	0.006		0.002	0.010
Males	$I^2$ (%)	12.3	8.7	0.003	4.9	1.0	$<0.001$	5.0	3.8	0.120
	Q test (p-value)	0.051	0.100		0.237	0.499		0.221	0.276
Females	$I^2$ (%)	18.8	12.1	$<0.001$	17.2	13.5	$<0.001$	7.9	3.6	$<0.001$
	Q test (p-value)	0.002	0.038		0.004	0.024		0.133	0.312
Cardiopulmonary	$I^2$ (%)	29.5	24.1	$<0.001$	19.4	14.9	0.019	9.3	6.8	$<0.001$
	Q test (p-value)	$<0.001$	$<0.001$		$<0.001$	0.014		0.090	0.168
Cardiovascular	$I^2$ (%)	18.1	14.3	$<0.001$	13.1	8.7	$<0.001$	6.8	5.2	0.037
	Q test (p-value)	0.003	0.016		0.026	0.106		0.166	0.238
Respiratory	$I^2$ (%)	21.9	17.9	0.004	9.5	8.0	0.028	12.2	10.1	0.061
	Q test (p-value)	$<0.001$	0.004		0.084	0.127		0.041	0.062

Note: RR, relative risk.