Table 1: Summary of studies characteristics included in the meta-analysis.

Quality score
Study
author
year
SourceStudy designAge of study population
(case/control)
Years of followupAscertain of cases
(prostate ca)
Blood omega-3 fatty acid level determinationLevel of comparison used(NOQAS**)Quality score
(NHS++)
Adjustment variables
S (4)C (2)E (3)

Harvei 1997 [100]NorwayNested case controlAve. 50 yo
(141/282)
19.2 years
(Ave. 11.6)
Cancer registriesSerum fatty acidsQuartiles3239/11Age, area of residence

Männist 2003 [101]FinlandNested case
control
50–69 yo
(198/198)
5–10 yearsCancer registry and histopathology reviewSerum fatty acidsQuartile2238/11Age, area of residence (urban/rural), level of education, body mass index, alcohol consumption, and the number of years of smoking

Chavarro 2007 [102]USNested case control40–84 yo
(476/476)
13 years Hospital record and histopathology reviewBlood level fatty acids Quintile2139/11Age, smoking status at baseline, and length of followup

Crowe
2008 [103]
NetherlandNested case control53–67 yo
(962/1061)
4.2 yearsNational and regional cancer registryBlood phospholipidQuintile2239/11Age, BMI, smoking, alcohol intake, level of education, marital status, and physical activity

Park 2009 [104]USANested case control45–75 yo
(376/729)
10 yearsTumor registryErythrocyte membrane fatty acidsQuartile and tertile22310/11Age, area of residence, race/ethnicity, family
history of prostate cancer, BMI, level of education, hour of fasting, date, and time of blood draws

Brasky 2011 [105]US Nested case control
(from PCPT)
55–84 yo
(1658/1803)
7 yearsEnd-study prostate biopsiesSerum fatty acidsQuartile4239/11Age, race, family history of prostate cancer, diabetes, BMI, alcohol, and treatment arm

Norrish 1999 [99]New ZealandCase control40–80 yo
(317/480)
N/AHistopathologyErythrocyte membrane fatty acidsQuartile3239/11Age, height, total nonsteroidal anti-inflammatory drug use, socioeconomic status, and food frequency questionnaire-estimated intake of total polyunsaturated fat

Shannon 2010 [97]USCase control50–86 yo
(127/183)
N/AHistopathologyErythrocyte membrane fatty acidsTertile3239/11Age, BMI, race, and family history of prostate cancer

Godley
1996 [94]
USCase control 45 yo
(89)(38)
N/AHistopathologyErythrocyte membrane fatty acidsQuartile3228/11Age and Race

Newcomer 2001 [95]USCase control41–66 yo
(67/156)
N/AHistopathologyErythrocyte membrane fatty acidsQuartile3138/11Age

Ukoli 2009 [96]NigeriaCase control≥45
(66/226)
N/AHistopathologySerum fatty acidsQuartile3239/11Age, level of education, family history of prostate cancer, and waist-hip ratio

Ukoli 2010 [98]NigeriaCase control≥45
(48/96)
N/AHistopathologySerum fatty acidsQuartile3239/11Age, level of education, family history of prostate cancer, and waist-hip ratio

**Newcastle-Ottawa Quality Assessment Score.
++National Health Service, UK, recommended critical appraisal of case control.
S: selection; C: comparability; E: exposure.