Table 1. Characteristics of studies on the association between serum vitamin D status and metabolic syndrome.
| Author, year | Study design (follow up period) | Location | Age (yrs) | No. of subjects | Criteria for metabolic syndrome | Serum vitamin D concentration (nmol/L) | OR or RR (95% CI) | Adjustments | Overall quality | |
|---|---|---|---|---|---|---|---|---|---|---|
| Cross-sectional studies | ||||||||||
| Ford et al., 2005 [32] | Cross-sectional | US | ≥ 20 | 8,421 | Modified NCEP ATP III | Q1 (≤ 48.4) | 1.00 | Age, sex, race/ethnicity, education, smoking status, cotinine concentration, total cholesterol concentration, C-reactive protein concentration, alcohol use, physical activity, fruit and vegetable intake, vitamin or supplement use, and season of study participation | 6 | |
| Q2 (48.5–63.4) | 0.82 (0.60–1.10) | |||||||||
| Q3 (63.5–78.1) | 0.75 (0.55–1.02) | |||||||||
| Q4 (78.2–96.3) | 0.60 (0.44–0.83) | |||||||||
| Q5 (≥ 96.4) | 0.46 (0.32–0.67) | |||||||||
| Reis et al., 2007 [21] | Cross-sectional | US | 44–96 | 1,070 | Modified NCEP ATP III | Men | Men | Age, current smoking, alcohol use, exercise, season of study participation, and hormone therapy (in women) | 9 | |
| I (< 87.5) | 1.00 | |||||||||
| II (87.5–97.4) | 0.83 (0.39–1.73) | |||||||||
| III (97.5–110) | 0.68 (0.32–1.43) | |||||||||
| IV (110.1–126.2) | 0.65 (0.32–1.34) | |||||||||
| V (≥ 126.3) | 0.57 (0.26–1.25) | |||||||||
| Women | Women | |||||||||
| I (< 77.5) | 1.00 | |||||||||
| II (77.5–92.4) | 0.96 (0.48–1.90) | |||||||||
| III (92.5–103.7) | 0.96 (0.51–1.79) | |||||||||
| IV (103.8–119.9) | 1.33 (0.69–2.57) | |||||||||
| V (≥ 120) | 0.88 (0.43–1.80) | |||||||||
| Hyppönen et al., 2008 [34] | Cross-sectional | UK | 42–46 | 6,810 | Modified NCEP ATP III | Lowest third (9–45) | 1.00 | Sex, month, hour of measurement, and insulin-like growth factor-I | 7 | |
| Middle third (46–67) | 0.58 (0.48–0.72) | |||||||||
| Highest third (68–231) | 0.33 (0.26–0.42) | |||||||||
| Lee et al., 2009 [36] | Cross-sectional | UK | 40–79 men | 3,069 | Modified NCEP ATP III | Q1 (< 35.7) | 1.00 | Age, smoking, alcohol consumption, physical activity, season and center, PTH, and HOMA-IR | 7 | |
| Q2 (35.7–49.4) | 0.94 (0.62–1.43) | |||||||||
| Q3 (49.5–65.1) | 0.78 (0.56–1.08) | |||||||||
| Q4 (65.2–85.9) | 0.61 (0.36–1.04) | |||||||||
| Q5 (> 85.9) | 0.60 (0.47–0.78) | |||||||||
| Lu et al., 2009 [37] | Cross-sectional | China | 50–70 | 3,262 | Modified NCEP ATP III | Q1 (≤ 28.7) | 1.00 | Age, sex, geographic location, residential region, visit date, education, physical activity, smoking, alcohol drinking, family history of CVD and diabetes, self-reported coronary heart disease and stroke, and inflammatory factors | 7 | |
| Q2 (28.8–36.8) | 0.94 (0.76–1.17) | |||||||||
| Q3 (36.9–45.5) | 0.71 (0.57–0.88) | |||||||||
| Q4 (45.6–57.6) | 0.58 (0.47–0.72) | |||||||||
| Q5 (≥ 57.7) | 0.40 (0.32–0.50) | |||||||||
| Kim et al., 2010 [35] | Cross-sectional | Korea | ≥ 40 | 1,330 | Modified NCEP ATP III | Q1 (10–29.7) | 1.00 | Age, gender, BMI, season of blood draw, smoking, drinking, exercise, total energy, Ca and sodium intake, PTH, and serum Ca levels | 9 | |
| Q2 (30–39.2) | 0.72 (0.47–1.09) | |||||||||
| Q3 (39.4–49.4) | 0.72 (0.46–1.12) | |||||||||
| Q4 (49.7–61.2) | 0.55 (0.35–0.89) | |||||||||
| Q5 (61.4–116.8) | 0.34 (0.21–0.58) | |||||||||
| Chacko et al., 2011 [31] | Cross-sectional | US | 50–79 women | 292 | Joint interim statement | T1 (< 35) | 1.00 | Age, race/ethnicity, month of blood draw, geographic region, case-control status, smoking status, alcohol intake, physical activity, supplemental vitamins (vitamin D, Ca, magnesium, multivitamins with minerals), and BMI | 7 | |
| T2 (35–51) | 0.43 (0.20–0.93) | |||||||||
| T3 (≥ 52) | 0.38 (0.16–0.91) | |||||||||
| Majumdar et al., 2011 [20] | Cross-sectional | India | 18–75 | 441 | Modified NCEP ATP III | Men | Men | Age, BMI, and smoking habits | 7 | |
| Q1 (< 28.2) | 1.00 | |||||||||
| Q2 (28.2–38.0) | 0.3 (0.1–0.9) | |||||||||
| Q3 (38.1–47.0) | 0.8 (0.3–2.0) | |||||||||
| Q4 (47.1–57.8) | 0.9 (0.3–2.3) | |||||||||
| Q5 (> 57.8) | 0.6 (0.2–1.7) | |||||||||
| Women | Women | |||||||||
| Q1 (< 25.2) | 1.00 | |||||||||
| Q2 (25.2–34.2) | 1.1 (0.4–3.4) | |||||||||
| Q3 (34.3–42.9) | 1.1 (0.4–3.4) | |||||||||
| Q4 (43.0–53.5) | 1.5 (0.5–4.9) | |||||||||
| Q5 (> 53.5) | 1.2 (0.4–3.6) | |||||||||
| Maki et al., 2012 [38] | Cross-sectional | US | ≥ 20 | 3,529 | Modified NCEP ATP III | Q1 (7.5–44.9) | 1.00 | Age, sex, race/ethnicity, education, smoking status, serum cotinine, C-reactive protein, alcohol use, physical activity, sum of total fruit and vegetable Healthy Eating Index scores, and daily intake of vitamin D from dietary supplements | 6 | |
| Q2 (45–59.9) | 0.75 (0.54–1.03) | |||||||||
| Q3 (60–74.9) | 0.69 (0.49–0.96) | |||||||||
| Q4 (75–215) | 0.40 (0.27–0.59) | |||||||||
| Bea et al., 2015 [30] | Cross-sectional | US | Mean 65 | 2,096 | Modified NCEP ATP III | Deficient (< 50) | 1.00 | Age, race/ethnicity, supplemental Ca, waist-hip ratio and sex | 9 | |
| Inadequate (50–75) | 0.70 (0.54–0.92) | |||||||||
| Adequate (≥ 75) | 0.47 (0.35–0.63) | |||||||||
| Huang et al., 2015 [33] | Cross-sectional | Taiwan | 22–39 | 355 | Modified NCEP ATP III | T1 (21.5–58.8) | 1.00 | Age, sex, smoking status, alcohol consumption, physical activity, BMI, and HOMA-IR | 8 | |
| T2 (58.9–79.4) | 0.81 (0.19–3.40) | |||||||||
| T3 (79.5–218.2) | 0.64 (0.14–2.89) | |||||||||
| Lu et al., 2015 [12] | Cross-sectional | China | 21–97 | 3,275 | International Diabetes Federation | < 25 | 1.00 | Age, sex, BMI, waist circumference, FPG, triglyceride, HDL-C, low-density lipoprotein, systolic blood pressure, and diastolic blood pressure | 7 | |
| 25–50 | 0.70 (0.46–1.06) | |||||||||
| 50–75 | 0.27 (0.15–0.46) | |||||||||
| ≥ 75 | 0.16 (0.06–0.38) | |||||||||
| Vitezova et al., 2015 [40] | Cross-sectional | Netherlands | ≥ 55 | 3,240 | Joint interim statement | < 50 | 1.00 | Age, sex, physical activity, diet quality score, family history of cardiometabolic diseases, baseline cardiometabolic diseases, smoking, education, income, season of blood draw, and year of blood draw | 8 | |
| 50–75 | 0.70 (0.58–0.84) | |||||||||
| ≥ 75 | 0.61 (0.49–0.77) | |||||||||
| Akter et al., 2017 [28] | Cross-sectional | Japan | 18–69 | 1,790 | Joint interim statement | < 50 | 1.00 | Age, sex, energy intake, smoking status, alcohol intake, physical activity, night or rotating shift work, Ca intake and BMI | 9 | |
| 50–75 | 0.79 (0.55–1.15) | |||||||||
| ≥ 75 | 0.52 (0.25–1.04) | |||||||||
| Pannu et al., 2017 [13] | Cross-sectional | Australia | 18–75 | 3,404 | Joint interim statement | Low (33) | 1.00 | Age, gender, country of birth, income, education, smoking, season, energy intake, physical activity level, body weight, alcohol, dietary fiber, magnesium, Ca, and retinol | 10 | |
| Medium (54) | 0.77 (0.58–1.04) | |||||||||
| High (77) | 0.35 (0.26–0.48) | |||||||||
| Huang et al., 2019 [41] | Cross-sectional | China | 49–86 women | 616 | International Diabetes Federation | Deficient (< 50) | 1.00 | Age, years after menopause, BMI, education, season of blood sampling, exercise, PTH, estradiol (pg/mL) | 7 | |
| Insufficient (50–75) | 0.76 (0.52–1.11) | |||||||||
| Sufficient (≥ 75) | 0.38 (0.22–0.66) | |||||||||
| Ganji et al., 2020 [43] | Cross-sectional | Qatar | 20–80 women | 700 | International Diabetes Federation | Q1 (< 32.5) | 1.00 | Age, income, education, and menopause | 8 | |
| Q2 (32.5–45) | 1.37 (0.88–2.15) | |||||||||
| Q3 (45–62.5) | 1.34 (0.85–2.13) | |||||||||
| Q4 (≥ 62.5) | 0.50 (0.29–0.85) | |||||||||
| Yeap et al., 2020 [42] | Cross-sectional | Australia | Mean 58.1 | 4,858 | International Diabetes Federation | < 50 | Males | Unadjusted | 5 | |
| 50–100 | 1.00 | |||||||||
| > 100 | 0.56 (0.37–0.86) | |||||||||
| 0.24 (0.15–0.86) | ||||||||||
| Females | ||||||||||
| 1.00 | ||||||||||
| 0.61 (0.46–0.81) | ||||||||||
| 0.37 (0.46–0.81) | ||||||||||
| Weldegiorgis et al., 2020 [44] | Cross-sectional | China | > 50 | 2,764 | Joint interim statement | Q1 (≤ 24.6) | 1.00 | Age, sex, cigarette status, alcohol consumption, physical activity, total serum cholesterol, low-density lipoprotein, and creatinine | 7 | |
| Q2 (24.6–35) | 0.76 (0.55–1.06) | |||||||||
| Q3 (35–48.7) | 0.74 (0.53–1.03) | |||||||||
| Q4 (≥ 48.8) | 0.67 (0.45–0.90) | |||||||||
| Cohort studies | ||||||||||
| Gagnon et al., 2012 [39] | Cohort (5 yrs) | Australia | ≥ 25 | 11,247 | Modified NCEP ATP III | Q1 (< 45) | 1.00 | Age, sex, ethnicity, season, latitude, smoking, family history of type 2 diabetes, physical activity, education, epidermal growth factor receptor, and HOMA-IR | 9 | |
| Q2 (45–57.5) | 1.26 (0.95–1.65) | |||||||||
| Q3 (60–67.5) | 0.87 (0.65–1.17) | |||||||||
| Q4 (70–82.5) | 0.91 (0.68–1.21) | |||||||||
| Q5 (85–232.5) | 0.72 (0.53–0.98) | |||||||||
| Amirbaigloo et al., 2013 [29] | Cohort (6.8 yrs) | Iran | ≥ 20 | 644 | Joint interim statement | < 50 | 1.00 | BMI, waist circumference, FPG, blood pressure, triglyceride, HDL-C, and smoking status | 8 | |
| 50–75 | 0.96 (0.66–1.39) | |||||||||
| > 75 | 1.01 (0.66–1.55) | |||||||||
| Pham et al., 2015 [16] | Cohort (1.1 yrs) | Canada | Mean 51 | 6,682 | Joint interim statement | < 50 | 1.00 | Gender, baseline age, season at baseline, season at follow-up, tobacco smoking status, alcohol drinking status, physical activity at baseline, and physical activity change during follow-up | 7 | |
| 50–75 | 0.78 (0.60–1.01) | |||||||||
| 75–100 | 0.49 (0.37–0.64) | |||||||||
| 100–125 | 0.37 (0.27–0.52) | |||||||||
| > 125 | 0.24 (0.16–0.34) | |||||||||
| Gao et al., 2017 [19] | Cohort (4 yrs) | China | Mean 46 | 474 | Chinese Diabetes Society | Men | Men | Age, physical activity, smoking, alcohol consumption, family history of obesity, diabetes, hypertension, hyperlipidemia and CVD, baseline weight, FPG, 2-hour postprandial glucose level, triglyceride, HDL-C, systolic blood pressure, and diastolic blood pressure | 7 | |
| Q1 (13.93–32.6) | 1.00 | |||||||||
| Q2 (32.61–39.15) | 1.00 (0.38–2.62) | |||||||||
| Q3 (39.16–45.15) | 0.88 (0.32–2.40) | |||||||||
| Q4 (45.15–64.14) | 0.29 (0.06–1.30) | |||||||||
| Women | Women | |||||||||
| Q1 (15.42–36.57) | 1.00 | |||||||||
| Q2 (36.58–41.71) | 0.82 (0.26–2.58) | |||||||||
| Q3 (41.72–49.49) | 0.66 (0.19–2.23) | |||||||||
| Q4 (49.5–80.3) | 0.33 (0.07–1.58) | |||||||||
OR, odds ratio; RR, relative risk; CI, confidence interval; NCEP ATP III, National Cholesterol Education Program Adult Treatment Panel III; PTH, parathyroid hormone; HOMA-IR, homeostasis model assessment of insulin resistance; CVD, cardiovascular disease; BMI, body mass index; Ca, calcium; FPG, fasting plasma glucose; HDL-C, high-density lipoprotein cholesterol.