Table 2. Stratified pooled relative risks and 95% confidence intervals for highest versus lowest category of dietary beta-carotene and all-cause mortality.

Subgroups		N	Death	Participants	RR	95%CI	I2 (%)	Pa	Pb
All studies		7	11810	149774	0.83	0.78, 0.88	1.00	0.416
Duration of follow-up									0.144
	<10 years	5	4133	88170	0.89	0.80, 0.98	0	0.555
	> = 10 years	2	7677	61604	0.79	0.73, 0.86	0	0.826
Sample size									0.902
	<10,000	3	1519	14341	0.83	0.70, 0.97	0	0.928
	> = 10,000	4	10291	135433	0.84	0.75, 0.94	49.30	0.116
Population age at baseline									0.255
	<50	4	4434	86131	0.87	0.78, 0.97	14.50	0.320
	> = 50	3	7376	63643	0.80	0.74, 0.86	0	0.843
Median intake									0.519
	<2500 ug/d	3	1762	48684	0.80	0.69, 0.92	0	0.722
	> = 2500 ug/d	3	9729	94075	0.86	0.75, 0.99	60.80	0.078
Validated FFQ									0.751
	Yes	4	10019	130819	0.83	0.74, 0.93	42.70	0.155
	No	3	1791	18955	0.85	0.73, 1.00	0	0.741
Major confounders adjusted
History of disease									0.071
	Yes	4	3571	46812	0.79	0.73, 0.85	0	0.852
	No	3	8239	102962	0.92	0.82, 1.03	0	0.920
Smoking and drinking									0.837
	Yes	5	10309	131994	0.83	0.76, 0.91	25.60	0.251
	No	2	1501	17780	0.85	0.72, 1.00	0	0.451
Physical activity									0.158
	Yes	4	8210	109615	0.80	0.74, 0.86	0	0.629
	No	3	3600	40159	0.89	0.80, 1.00	0	0.457
Serum cholesterol level									0.751
	Yes	3	1791	18955	0.85	0.73, 1.00	0	0.741
	No	4	10019	130819	0.83	0.74, 0.93	42.70	0.155
Vitamin supplementation use									0.302
	Yes	2	7057	56628	0.79	0.73, 0.86	0	0.574
	No	5	4753	93146	0.87	0.79, 0.96	0	0.461

Abbreviation: RR, relative risk; CI, confidence interval; I ², measure of heterogeneity; P_a, P value for heterogeneity within each group; P_b, P value for heterogeneity between subgroups in meta-regression.