Table 3. Characteristics of papers included in the meta-analysis.
| First Author, year | Study design | Population (Study period) | Cases # | Total # | Age (years) range/mean | Source of Zinc | Highest category | Stratification/Adjustment variables |
|---|---|---|---|---|---|---|---|---|
| Kolonel, 1988 | case-control | Hawaii, USA: 37% Japanese, 31% white (1977–1983) | 452 | 1351 | >70 (43%) & ≤70 (57%) | Dietary & supplements | >100 (mg/day) | Stratified by Age (<70 & ≥70); zinc intake (dietary & total); Adjusted for ethnicity |
| West, 1991 | case-control | Utah, USA: LDS members (1984–1985) | 358 | 1037 | 45–74 | Dietary | >16 (mg/day) | Matched by age and residence; stratified by age (45–67; 68–74) and pathology (all tumors, aggressive tumor; adjustment for energy and age |
| Andersson, 1996 | case-control | Sweden (1989–1994) | 526 | 1062 | 45–74 | Dietary | >13.5 (mg/day) | Stratified by pathology (all stages & advanced); adjusted for age, energy |
| Key, 1997 | case-control | UK (1990–1994) | 328 | 656 | 68.1 | Dietary | ≥ 11 (mg/day) | Matched for age; adjusted for social class |
| Vlajinac, 1997 | case-control | Serbia (1990–1994) | 101 | 303 | 70.5 cases & 71.5 control | Dietary | NR | Matched for age, hospital admittance and place of residence; adjusted for energy, protein, total fat, saturated fatty acids, carbohydrates, total sugar, fiber, retinol equivalent, alpha-tocopherol, folic acid, vitamin B12, potassium, calcium, phosphorous, magnesium and iron |
| Lee, 1998 | case-control | China (1989–1992) | 133 | 398 | 50–80 | Dietary | NR | Adjusted for region, fat, carotenoids and selenium |
| Kristal,1999 | case-control | Washington, USA: 95–98% white (1993–1996) | 697 | 1363 | 40–64 | Supplements | ≥ 7 (frequency/week) | Stratified by stage and grade; adjusted for age, energy, fat, race, family history, BMI, PSA testing, education |
| Platz, 2002 | nested case-control | CLUEII cohort, USA (1989–1996) | 115 | 342 | 59–74 | Toe nail | 259.1 (ppm) | Matched on age, race, date of blood collection and size of toenail clipping; adjusted for education, adult height, current BMI, BMI at age 21, father or brother with prostate cancer, cigarette smoking, and multivitamin use |
| Litzmann, 2003 | cohort | Health professionals cohort, USA (1986–2000) | 2901 | 46974 | 44–66 | Supplements | 101 mg | Stratified by stage; adjusted for age, energy, BMI, height, smoking, family history, physical activity, aspirin use, dietary calcium, supplemental calcium, fructose, supplemental vitamin E, tomato-based foods, fish, red meat, and alpha -linolenic acid. |
| Meyer, 2005 | RCT | SU.VI.MAX trial, Canada (1994–2004) | 101 | 4830 | 45–60 | Serum | ≥ 13.4 mmol/L | Matched for age, PSA, smoking, BMI, serumβ-carotene, α-tocopherol, vitamin C, Selenium |
| Gallus, 2007 | case-control | multicenter hospital study from Italy (1991–2002) | 1294 | 2745 | 46–74 | Dietary | >15.65 (mg/day) | Adjusted for age, study center, education, physical activity, family history, BMI and total energy intake |
| Zhang, 2009 | case-control | Case-Control Surveillance Study: 77–84% White, USA (1976–2006) | 1706 | 4110 | 40–79 | Supplements | ≥10 years | Adjusted for matching variables age, study center, year of interview and race, and for education, BMI, alcohol, current smoking, family history, use of other vitamins & mineral supplements. |
| Gonzalez, 2009 | cohort | Vitamin and Lifestyle cohort: 93–94% white, USA (2000–2004) | 832 | 35244 | 50–76 | Dietary & supplements | 152 mg/day | Stratified by zinc category, stage, grade &vegetable and fruit intake; adjusted for education, race, family history, PSA-test within the 2 years prior to baseline, & current multivitamin use. |
| Kristal, 2010 | cohort | Prostate cancer prevention trial: 93–94% white, USA& Canada (1994–2003) | 1703 | 9559 | cases: 63.6 & controls: 62.6 | Dietary & supplements | >22 mg/day | Adjusted for age, race, family history, treatment arm, BMI and pathology |
| Karimi, 2012 | case-control | Hospital-based study from Malaysia: 47% Malays, 33% Chinese and 20% Indians (2010–2012) | 50 | 50 | 50–86 | Hair and Nails | hair: >3.75 mg/g & Nails: >3.32 mg/g | Matched for age and ethnicity |
| Park, 2013 | Nested case-control | Multiethnic cohort study from Hawaii and California USA: 46% AA, 20% Japanese (1993–2006) | 392 | 1175 | 45–75 | Serum | >102.5 μg/dl | Matched for geographic location, race, birth year, date of blood draw, time of blood draw, and fasting hours prior to blood draw, family history, BMI, and education |
Abbreviations: AA: African American, RCT: Randomized control-trial, BMI: body mass index