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Table 2 Subgroup analysis for the effect of omega–3 fatty acid supplementation on cancer incidence, nonvascular death, and total mortality

From: Effect of omega-3 fatty acid supplementation on cancer incidence, non-vascular death, and total mortality: a meta-analysis of randomized controlled trials

Outcomes Group Number of study RR and 95% CI P value Heterogeneity (%) P value for heterogeneity P value for interaction test
Cancer incidence Publication year
Before 2000 5 1.07 (0.85–1.34) 0.56 0 0.87 0.789
After 2000 6 1.11 (0.96–1.28) 0.15 0 0.93
Number of patients
>1000 5 1.10 (0.97–1.24) 0.12 0 0.98 0.878
<1000 6 1.03 (0.45–2.38) 0.94 0 0.83
Percent men (%)
>80 7 1.06 (0.87–1.28) 0.58 0 0.98 0.608
<80 4 1.13 (0.97–1.31) 0.13 0 0.72
Mean age
>64 1 5.00 (0.24–103.28) 0.30 0.328
<64 10 1.10 (0.97–1.24) 0.13 0 1.00
Intervention
Alpha–linolenic acid 1 0.33 (0.01–8.09) 0.50 0.481
Long–chain n–3 PUFA 10 1.10 (0.98–1.24) 0.12 0 0.99
Primary or secondary prevention
Primary 1 1.11 (0.93–1.33) 0.26 0.882
Secondary 10 1.09 (0.93–1.28) 0.29 0 0.98
Duration of the follow–up period (months)
>36 4 1.10 (0.97–1.24) 0.14 0 0.98 0.883
<36 7 1.16 (0.58–2.33) 0.68 0 0.88
Jadad score
>4 6 1.11 (0.96–1.30) 0.16 0 0.98 0.771
<4 5 1.07 (0.88–1.30) 0.49 0 0.77
Nonvascular death Publication year
Before 2000 5 0.93 (0.77–1.13) 0.47 0 0.82 0.440
After 2000 11 1.01 (0.93–1.10) 0.75 0 0.86
Number of patients
>1000 8 1.01 (0.93–1.09) 0.89 0 0.89 0.328
<1000 8 0.77 (0.45–1.32) 0.34 0 0.80
Percent men (%)
>80 9 0.93 (0.80–1.08) 0.37 0 0.78 0.219
<80 6 1.04 (0.94–1.14) 0.47 0 0.92
Mean age
>64 7 1.01 (0.86–1.19) 0.89 0 0.83 0.916
<64 9 1.00 (0.91–1.09) 0.94 0 0.78
Intervention
Alpha–linolenic acid 3 0.95 (0.32–2.85) 0.93 0 0.54 0.927
Long–chain n–3 PUFA 13 1.00 (0.93–1.08) 1.00 0 0.89
Primary or secondary prevention
Primary 3 1.01 (0.87–1.18) 0.87 31.6 0.23 0.754
Secondary 13 0.98 (0.88–1.10) 0.78 0 0.97
Duration of the follow–up period (months)
>36 7 0.99 (0.92–1.08) 0.85 0 0.68 0.460
<36 9 1.11 (0.83–1.49) 0.49 0 0.92
Jadad score
>4 8 1.02 (0.93–1.11) 0.71 0 0.62 0.427
<4 8 0.95 (0.82–1.11) 0.54 0 0.97
Total mortality Publication year
Before 2000 5 0.79 (0.67–0.93) 0.005 19 0.30 0.009
After 2000 12 1.00 (0.94–1.08) 0.90 29 0.16
Number of patients
>1000 9 0.98 (0.91–1.06) 0.57 57 0.02 0.014
<1000 8 0.67 (0.50–0.90) 0.007 0 0.59
Percent men (%)
>80 9 0.80 (0.65–0.98) 0.03 64 0.005 0.033
<80 7 1.01 (0.95–1.08) 0.71 0 0.84
Mean age
>64 7 0.96 (0.89–1.02) 0.20 0 0.44 0.543
<64 10 0.92 (0.82–1.04) 0.18 62 0.004
Intervention
Alpha–linolenic acid 3 0.58 (0.35–0.98) 0.04 0 0.46 0.058
Long–chain n–3 PUFA 14 0.96 (0.89–1.04) 0.36 47 0.03
Primary or secondary prevention
Primary 3 0.99 (0.86–1.14) 0.91 46 0.15 0.566
Secondary 14 0.94 (0.84–1.04) 0.21 47 0.03
Duration of the follow–up period (months)
>36 8 0.98 (0.91–1.05) 0.54 47 0.06 0.157
<36 9 0.80 (0.61–1.05) 0.11 43 0.08
Jadad score
>4 9 0.98 (0.91–1.06) 0.65 30 0.18 0.320
<4 8 0.88 (0.72–1.07) 0.19 59 0.02