Table 2. Subgroup analyses per 0.5% increment^a of blood EPA^b concentration and risk of PCa.

Subgroup factor	Number of studies	Relative risk (95% CI)	Heterogeneity within subgroup		Heterogeneity between subgroups	Nonlinearity
			I2	Degree	P value	P value
Overall analysis	9	1.01 (0.99, 1.04)	6%	Low	—	0.88
Study design
Nested case-control	7	1.01 (0.98, 1.04)	12%	Low	0.39	0.50
Case-cohort	2	—	—		—	—
Grade or stage of cancer
Aggressive	5	—	—	—	—	<0.01
Non-aggressive	4	1.02 (0.98, 1.07)	11%	Low		0.23
Follow-up duration
≤7.4 years	6	1.02 (1.00, 1.04)	0%	Low	0.19	0.40
>7.4 years	3	0.98 (0.91, 1.06)	37%	Moderate		0.39
Regions
USA	5	1.01 (0.94, 1.10)	47%	Moderate	0.49	<0.01
European countries	3	1.02 (0.99, 1.04)	0%	Low		0.56
Australia	1	—	—	—	—	—
Covariate adjustment
Adjusted for age	5	1.01 (0.94, 1.10)	46%	Moderate	0.49	0.01
Not adjusted for age	4	1.02 (0.99, 1.04)	0%	Low		0.16
Adjusted for BMI	4	1.02 (1.00, 1.05)	0%	Low	0.34	0.20
Not adjusted for BMI	5	1.00 (0.95, 1.06)	33%	Moderate		0.38
Adjusted for alcohol consumption	4	1.02 (1.00, 1.05)	0%	Low	0.27	0.19
Not adjusted for alcohol consumption	5	1.00 (0.94, 1.06)	30%	Moderate		0.44
Adjusted for smoking status	4	1.01 (0.95, 1.07)	51%	Moderate	0.93	0.08
Not adjusted for smoking status	5	1.02 (0.96, 1.07)	0%	Low		0.20
Adjusted for family history of PCa	4	1.00 (0.95, 1.04)	41%	Moderate		0.42
Not adjusted for family history of PCa	5	1.04 (0.98, 1.10)	0%	Low		0.53
Risk expression
Hazard/rate ratio	2	—	—		—	—
Relative risk	2	—	—		—	—
Odds ratio	5	1.02 (0.96, 1.07)	0%	Low	0.99	0.40

BMI, body mass index; CI, confidence interval; PCa, prostate cancer.

^aThe range of blood EPA concentration in the included studies is 0.22% to 5.72%.

^bEPA, eicosapentaenoic acid.