Table 2. Subgroup analyses of all-cause and cardiovascular mortality.

Subgroups	Number of studies	Pooled hazard risk	95% confidence interval	Heterogeneity between studies
1. All-cause mortality
Study design
Prospective study	5	1.29	1.05 to 1.59	P = 0.042; I2 = 51.8%
Retrospective study	3	1.99	1.33 to 2.99	P = 0.125; I2 = 42.1%
Region
Asia	6	1.35	1.09 to 1.67	P = 0.030; I2 = 51.4%
America	2	1.85	1.15 to 2.98	P = 0.082; I2 = 55.2%
Patient population
Hemodialysis	6	1.33	1.10 to 1.62	P = 0.031; I2 = 49.5%
Peritoneal dialysis	2	2.36	1.54 to 3.60	P = 0.692; I2 = 0.0%
Sample sizes
>500	2	1.36	1.08 to 1.72	P = 0.195; I2 = 32.1%
<500	6	1.59	1.13 to 2.26	P = 0.005; I2 = 65.4%
Follow-up duration
≥4 years	3	1.23	1.09 to 1.38	P = 0.088; I2 = 50.5%
<4 years	5	1.78	1.45 to 2.19	P = 0.256; I2 = 21.0%
Grade of AAC
Grade 1	4	1.35	1.03 to 1.77	P = 0.669; I2 = 0.0%
Grade 2 + 3	4	1.55	1.13 to 2.12	P = 0.079; I2 = 49.3%
2. Cardiovascular mortality
Study design
Prospective study	5	2.22	1.70 to 2.88	P = 0.809; I2 = 0.0%
Retrospective study	1	4.71	1.51 to 14.71	P = 0.744; I2 = 0.0%
Region
Asia	4	2.25	1.66 to 3.06	P = 0.550; I2 = 0.0%
America	2	2.42	1.51 to 3.87	P = 0.803; I2 = 0.0%
Patient population
Hemodialysis	4	2.10	1.59 to 2.77	P = 0.893; I2 = 0.0%
Peritoneal dialysis	2	3.93	2.02 to 7.64	P = 0.881; I2 = 0.0%
Sample sizes
>500	1	1.86	1.24 to 2.81	P = 0.559; I2 = 0.0%
<500	5	2.63	1.90 to 3.65	P = 0.853; I2 = 0.0%
Follow-up duration
≥4 years	3	2.01	1.46 to 2.77	P = 0.8105; I2 = 0.0%
<4 years	3	2.91	1.91 to 4.43	P = 0.814; I2 = 0.0%
Grade of AAC
Grade 1	3	1.91	1.10 to 3.30	P = 0.674; I2 = 0.0%
Grade 2 + 3	3	2.31	1.57 to 3.40	P = 0.393; I2 = 0.0%

AAC, aortic arch calcification.