Table 2.
Characteristics and main findings of meta-analyses of observational studies reporting unique cognitive, infectious, metabolic, neonatal/infant/child related, pregnancy related, skeletal, and other outcomes (direction of comparison is high versus low)
| Outcome | Biomarker | Meta-analysis metric | Units | No of studies in each MA | No of events | Total No | Relative risk (95% CI)* | P value | I2 (95% CI) | Egger test P value |
|---|---|---|---|---|---|---|---|---|---|---|
| Cognitive disorders | ||||||||||
| Alzheimer’s disease | 25OHD | SMD (to OR) | NA | 7 | 357 | 1005 | 0.08 (0.01 to 0.63) | 0.02 | 98 (97 to 98) | 0.32 |
| Cognition | 25OHD | OR | NA | 7 | 1217 | 9004 | 0.42 (0.34 to 0.53) | 2.2×10−13 | 56 (0 to 79) | 0.16 |
| Depression (case-control studies) | 25OHD | OR | NA | 9 | 2051 | 19 807 | 0.77 (0.59 to 1.00) | 0.05 | 53 (0 to 76) | 0.22 |
| Depression (cohort studies) | 25OHD | HR | NA | 3 | 617 | 8815 | 0.44 (0.27 to 0.72) | 0.001 | 28 (0 to 80) | 0.49 |
| Infectious diseases | ||||||||||
| Tuberculosis | 25OHD | SMD (to OR) | NA | 7 | 308 | 534 | 0.29 (0.19 to 0.46) | 2.0×10−7 | 41 (0 to 74) | 0.79 |
| Metabolic disorders | ||||||||||
| Body mass index | 25OHD | Z score | NA | 37 | NA | 16 525 | −0.15 (−0.19 to −0.11) | 8.9×10−13 | NA | NA |
| Metabolic syndrome (prevalent) | 25OHD | OR | NA | 8 | 2821 | 31 416 | 0.49 (0.38 to 0.64) | 1.4×10−7 | 38 (0 to 71) | 0.59 |
| Type 2 diabetes | 25OHD | OR | NA | 16 | 4877 | 72 204 | 0.63 (0.56 to 0.69) | 5.0×10−17 | 1 (0 to 46) | 0.58 |
| Type 2 diabetes (prevalent) | 25OHD | OR | NA | 9 | 2424 | 11 892 | 0.45 (0.25 to 0.82) | 0.008 | 79 (56 to 87) | 0.96 |
| Neonatal/infant/child related outcomes | ||||||||||
| Birth length | 25OHD | WMD | cm | 2 | NA | 840 | 0.19 (−0.26 to 0.65 ) | 0.41 | NA | NA |
| Birth weight | 25OHD | WMD | grams | 4 | NA | 5541 | 130.9 (75.1 to 186.7) | 5.5×10−6 | NA | NA |
| Head circumference | 25OHD | WMD | cm | 2 | NA | 840 | 0.05 (−0.24 to 0.34) | 0.76 | NA | NA |
| Small for gestational age | 25OHD | OR | NA | 6 | NA | 6851 | 0.54 (0.44 to 0.67) | 1.8×10−8 | 8 (0 to 64) | 0.81 |
| Pregnancy related outcomes | ||||||||||
| Gestational diabetes | 25OHD | OR | NA | 10 | 687 | 4112 | 0.67 (0.53 to 0.85) | 0.0009 | 0 (0 to 53) | 0.58 |
| Pre-eclampsia | 25OHD | OR | NA | 9 | 393 | 3230 | 0.56 (0.39 to 0.8) | 0.002 | 0 (0 to 58) | 0.96 |
| Skeletal outcomes | ||||||||||
| Fractures | 25OHD | SMD (to OR) | NA | 28 | 1572 | 2956 | 0.31 (0.23 to 0.42) | 1.3×10−13 | 77 (66 to 83) | 0.78 |
| Hip fracture (hospital based controls) | 25OHD | log ratio of geometric mean | nmol/L | 8 | 1116 | 2201 | −0.26 (−0.33 to −0.23) | NA | NA | NA |
| Hip fracture (population based controls) | 25OHD | log ratio of geometric mean | nmol/L | 9 | 818 | 1655 | −0.51 (−0.64 to −0.38) | NA | NA | NA |
| Other outcomes | ||||||||||
| All cause mortality (in CKD patients) | 25OHD | RR | NA | 10 | 2110 | 6853 | 0.86 (0.81 to 0.92) | 4.6×10−6 | 31 (0 to 66) | 0.09 |
| All cause mortality | 25OHD | HR | NA | 18 | 15 447 | 77 155 | 0.72 (0.66 to 0.78) | 2.9×10−13 | 82 (72 to 87) | 0.29 |
CKD=chronic kidney disease; HR=hazard ratio; MA=meta-analysis; NA=not applicable; OR=odds ratio; RR=relative risk; SMD=standardised mean difference; WMD=weighted mean difference.
P values were estimated using formulas presented in Altman and Bland 2011.140
*Effect estimate and 95% CI estimated based on random effects model. Reported effect estimates and 95% CI are presented for hip fracture (population based controls), hip fracture (hospital based controls), birth length, head circumference, and birth weight.