Table 2. Subgroup analyses of vitamin D supplement for cancer incidence and mortality.

Variables	Subgroups	Studies (n)	RR	95% CI	P	I2 (%)	PHeterogeneity
Incidence
Gender	Both men and women	7	1.00	0.95–1.06	0.957	0.0	0.750
	Only women	3	0.80	0.58–1.11	0.188	65.9	0.053
History of cancer	Without	7	0.99	0.94–1.04	0.667	4.9	0.390
	With	3	0.92	0.76–1.11	0.394	43.5	0.171
Extra use of vitamin D	Without extra use of vitamin D	5	0.98	0.91–1.05	0.964	0.0	0.688
	With extra use of vitamin D	4	0.99	0.92–1.07	0.844	35.1	0.202
Ca supplement	Without	9	0.99	0.95–1.03	0.566	0.0	0.540
	With	1	0.58	0.31–1.07	0.083	NA	NA
Mortality
Gender	Both men and women	6	0.85	0.76–0.96	0.009	0.0	0.923
	Only women	1	0.90	0.78–1.04	0.140	NA	NA
History of cancer	Without	6	0.88	0.80–0.97	0.007	0.0	0.941
	With	1	0.77	0.53–1.12	0.167	NA	NA
Extra use of vitamin D	Without extra use of vitamin D	4	0.87	0.75–1.02	0.090	0.0	0.793
	With extra use of vitamin D	3	0.87	0.78–0.97	0.016	0.0	0.720
Ca supplement	Without Ca supplement	4	0.87	0.75–1.02	0.090	0.0	0.793
	With Ca supplement	3	0.87	0.78–0.97	0.016	0.0	0.720

Abbreviations: Ca, calcium; NA, not available; Vit D, vitamin D.