Table 2. Subgroup analyses of the association between periodontitis and cancer incidence.

Subgroups	No. of studies	Meta-analysis			Heterogeneity
		HR	95%CI	P-value	I2(%)	P -value
Breast Cancer
Study population
North America	4	1.12	1.05-1.19	0.001	0.0	0.694
Asia	3	1.16	1.00-1.35	0.044	53.1	0.119
Europe	3	1.76	1.06-2.91	0.029	75.8	0.016
South America	1	1.55	1.14-2.11	0.006	–	–
Study design
Prospective study	9	1.22	1.07-1.40	0.004	78.7	0.000
Retrospective study	2	1.52	1.17-1.98	0.002	0.0	0.832
Dental status
Self-reported	4	1.15	1.09-1.22	<0.001	0.0	0.502
Dental examination	7	1.38	1.00-1.90	0.051	83.1	0.000
Follow-up (years)
≥10	6	1.11	1.03-1.19	0.005	14.4	0.322
<10	5	1.43	1.15-1.78	0.001	86.3	0.000
Adjust for smoking
Yes	7	1.13	1.07-1.21	<0.001	7.7	0.369
No	4	1.47	1.07-2.01	0.016	90.3	0.000
Prostate cancer
Study population
North America	3	1.03	0.89-1.18	0.728	36.9	0.205
Asia	1	1.14	0.99-1.31	0.065	–	–
Europe	3	1.73	1.39-2.16	<0.001	39.8	0.190
Study design
Prospective study	7	1.26	1.03-1.54		72.9	0.001
Dental status
Self-reported	3	1.12	0.86-1.47	0.395	70.6	0.034
Dental examination	4	1.44	1.02-2.02	0.036	77.1	0.004
Follow-up (years)
≥10	6	1.16	0.97-1.38	0.100	60.8	0.026
<10	1	1.84	1.36-2.49	<0.001	–	–
Adjust for smoking
Yes	5	1.11	1.01-1.22	0.035	43.7	0.130
No	2	1.95	1.46-2.61	<0.001	43.8	0.182
Lung & bronchus cancer
Study population
North America	8	1.34	1.24-1.46	<0.001	46.9	0.068
Asia	3	1.18	0.72-1.93	0.502	59.8	0.083
Europe	3	1.11	0.64-1.95	0.709	77.6	0.004
Study design
Prospective study	11	1.30	1.10-1.53	0.002	68.5	<0.001
Retrospective study	3	1.36	1.14-1.63	0.001	34.4	0.218
Dental status
Self-reported	6	1.31	1.21-1.42	<0.001	0.0	0.635
Dental examination	8	1.33	0.94-1.88	0	75.7	<0.001
Follow-up (years)
≥10	9	1.28	1.18-1.38	<0.001	46.5	0.060
<10	5	1.20	0.81-1.77	0.368	78.8	<0.001
Adjust for smoking
Yes	10	1.35	1.25-1.46	<0.001	44.6	0.062
No	4	1.10	0.76-1.59	0.618	69.3	0.011
Colorectal Cancer
Study population
North America	7	1.08	0.98-1.19	0.134	18.2	0.291
Asia	4	1.22	0.97-1.55	0.089	91.4	<0.001
Europe	2	1.10	0.68-1.78	0.686	64.9	0.058
Study design
Prospective study	11	1.19	0.99-1.43	0.063	81.8	<0.001
Retrospective study	2	1.24	1.16-1.33	<0.001	0.0	0.327
Dental status
Self-reported	8	1.19	1.02-1.39	0.030	87.2	<0.001
Dental examination	5	1.17	0.92-1.48	0.203	26.4	0.236
Follow-up (years)
≥10	9	1.21	0.99-1.48	0.065	85.4	<0.001
<10	4	1.24	1.16-1.33	<0.001	35.9	0.182
Adjust for smoking
Yes	10	1.20	1.13-1.26	<0.001	45.2	0.058
No	3	1.08	0.71-1.63	0.718	90.3	<0.001
Total cancer
Study population
North America	6	1.13	1.09-1.18	<0.001	0.0	0.965
Asia	3	1.09	0.94-1.27	0.243	92.6	<0.001
Europe	3	1.18	1.09-1.28	<0.001	47.1	0.129
Study design
Prospective study	11	1.15	1.09-1.20	<0.001	67.1	<0.001
Retrospective study	1	0.84	0.58-1.19	0.324	–	–
Dental status
Self-reported	5	1.17	1.12-1.22	<0.001	57.1	0.054
Dental examination	7	1.08	1.03-1.13	0.001	46.1	0.072
Follow-up (years)
≥10	8	1.11	1.08-1.15	<0.001	42.1	0.097
<10	4	1.22	1.18-1.25	<0.001	49.0	0.097
Adjust for smoking
Yes	8	1.13	1.09-1.17	<0.001	0.0	0.803
No	4	1.18	1.06-1.32	0.002	86.2	<0.001

Notes.

CI

confidence interval

HR

hazard ratio