Low 25-hydroxyvitamin D levels and the risk of frailty syndrome: a systematic review and dose-response meta-analysis

Table 2 Frailty risk per 25 nmol/L increase in serum 25-hydroxyvitamin D in subgroup meta-analyses of the cross-sectional studies and the prospective cohort studies

Group	Subgroup	No.	OR/RR (95% CI)	I² (%)	P
Cross-sectional studies
Geographic location	Europe	4	0.78 (0.68–0.88)	50.6	0.108
Geographic location	United States	2	0.98 (0.94–1.01)	79.8	0.026
Definition of frailty	Phenotype	4	0.95 (0.89–1.01)	81.1	0.001
Definition of frailty	Others	2	0.76 (0.68–0.85)	0.0	0.612
Method of ^a25OHD assessment	^bLC-MS/MS	2	0.98 (0.94–1.01)	79.8	0.026
Method of ^a25OHD assessment	Others	4	0.78 (0.68–0.88)	50.6	0.108
^cKey-sets of covariates	Yes	3	0.87 (0.75–1.02)	80.1	0.007
^cKey-sets of covariates	No	3	0.81 (0.63–1.04)	89.6	< 0.001
^dNewcastle-Ottawa Scale	≥ 7	3	0.81 (0.71–0.91)	41.4	0.182
^dNewcastle-Ottawa Scale	< 7	3	0.95 (0.95–1.02)	86.9	< 0.001
Prospective cohort studies
Definition of frailty	Phenotype	2	0.89 (0.84–0.94)	0.0	0.877
Definition of frailty	Others	2	0.89 (0.76–1.04)	22.8	0.255
Follow-up (years)	≥ 5.6	2	0.90 (0.85–0.95)	0.0	0.510
Follow-up (years)	< 5.6	2	0.86 (0.72–1.02)	0.0	0.403
^cKey-sets of covariates	Yes	2	0.90 (0.85–0.95)	0.0	0.510
^cKey-sets of covariates	No	2	0.86 (0.72–1.02)	0.0	0.403

^a25OHD 25-hydroxyvitmain D, ^bLC-MS/MS liquid chromatography tandem-mass spectrometry ^cKey-sets of covariates: age, sex, season of blood draw, body mass index (or obesity), smoking, and physical activity; ^dNewcastle-Ottawa Scale: Total score could range from 0 to 9

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