(1) Baseline characteristics of the study population
The present study population was composed of 2493 participants, with an average age of 85 years, and consisted of 1197 males and 1296 females. The proportions of people with vitamin D insufficiency (20£25(OH)D<30 ng/mL) and vitamin D deficiency (25(OH)D <20 ng/ml) were 35.1% and 47.3%, respectively. Their average age was 85.7 years, which was older than that of the vitamin D-sufficient group (p<0.01). The vitamin D level of people with MetS based on the modified ATP Ⅲ criteria but without MetS based on the modified criteria (2012) was 21.22 ng/ml, which was significantly lower than that of individuals with MetS based on the modified criteria (2012) but without MetS based on the modified ATP Ⅲ criteria (23.63 ng/ml). The ages of these two groups were 83.60 and 84.72 years, respectively. The other characteristics of the total study population are shown in Table 2 and Figure 1.
There was no significant difference in blood pressure, fasting blood sugar or HDL-C among the vitamin D-sufficient group, the vitamin D-insufficient group and the vitamin D-deficient group (p>0.05). The weight, height, triglyceride levels and WC were significantly different among the three groups (p<0.05). Moreover, there were significant differences in the waist-hip ratio among the three groups (p<0.05). The percentage of people with an appropriate waist-hip ratio was higher in the vitamin D-sufficient group than in the other two groups. The prevalence of MetS was lowest in the vitamin D-sufficient group and highest in the vitamin D-deficient group regardless of the criteria used for the diagnosis of MetS. The difference in the prevalence of MetS based on the modified ATP III criteria and modified criteria (2012) was statistically significant between the groups (p<0.01).
(2) The relationship between vitamin D status and MetS
In the analysis of the basic model (model 1), with adjustments for only age and sex, each 10 ng/ml increase in serum 25(OH)D was significantly associated with a decreased prevalence of MetS according to the modified ATP Ⅲ criteria (OR: 0.92, 95% CI: 0.84, 1.00). After adjusting for other potential confounders, including nationality, education level, marital status, smoking, alcohol consumption, regular physicals and BMI (model 2), the results were still statistically significant (OR: 0.79, 95% CI: 0.69, 0.90). The vitamin D-sufficient group had a lower risk of MetS the vitamin D-deficient group based on model 2 (OR: 0.63, 95% CI: 0.52, 0.92). We applied the same analysis of MetS according to the CDS criteria and the modified criteria (2012). A similar significant relationship between vitamin D levels and MetS based on the CDS criteria was found. No statistically significant association was found between vitamin D levels and MetS based on the modified criteria (2012) (see Table 3 for details).
(3) The relationships between vitamin D and the individual components of MetS
We also analyzed the relationships of each MetS component and waist-hip ratio with vitamin D. Each 10 ng/ml increase in serum vitamin D was significantly associated with a decreased risk of elevated triglycerides (OR: 0.60, 95% CI: 0.51, 0.71), reduced HDL-C (OR: 0.67, 95% CI: 0.58-0.78) and elevated glucose (OR: 0.88, 95% CI: 0.78, 0.99) based on model 2. The vitamin D-sufficient group had a lower risk of elevated triglycerides (OR: 0.38, 95% CI: 0.25,0.56) and reduced HDL-C (OR: 0.47,95% CI: 0.32, 0.69) than the vitamin D-deficient group based on model 2. After further adjustment for other components of MetS, we still found significant associations between each 10 ng/ml increase in serum 25(OH)D and elevated triglycerides, reduced HDL-C and elevated glucose. The vitamin D-sufficient group had a lower risk of elevated triglycerides (OR: 0.46, 95% CI: 0.30, 0.71) and reduced HDL-C (OR: 0.64, 95% CI: 0.42, 0.97) than the vitamin D-deficient group after further adjustment for other components of MetS (see Table 4 for details).
(4) Sensitivity analysis
Table 5 shows the results of the sensitivity analyses. When individually excluding participants (if they suffered from multiple diseases, had inadequate mobility, or were younger than 80 years old) from the model, the estimates of the ORs for vitamin D and MetS remained statistically significant and were very similar to the estimates in the main analyses.
Table2. Multiple logistic regression and subgroup analysis for the association of metabolic syndrome based on different diagnostic criterias with vitamin D status
variables
|
25(OH)D[OR (95%CI)]
|
continuous
|
<20ng/ml
|
20—30ng/ml
|
≥30ng/ml
|
MetS [modified ATP Ⅲ]
|
|
|
|
|
Model1
|
0.92(0.84to1.00)
|
reference
|
0.88(0.73to1.07)
|
0.83(0.66to1.04)
|
Model2
|
0.79(0.69to0.90)
|
reference
|
0.70(0.52to0.92)
|
0.63(0.45to0.88)
|
MetS[Modified Criteria(2012)]
|
|
|
|
|
Model1
|
1.08(0.99to1.18)
|
reference
|
1.13(0.92to1.38)
|
1.07(0.85to1.35)
|
Model2
|
1.08(0.94to1.24)
|
reference
|
0.94(0.68to1.30)
|
1.06(0.73to1.55)
|
Mets (CDS)
|
|
|
|
|
Model1
|
0.70(0.63to0.78)
|
reference
|
0.50(0.36to0.79)
|
0.54(0.41to0.70)
|
Model2
|
0.63(0.54to0.74)
|
reference
|
0.71(0.60to0.69)
|
0.46(0.31to0.69)
|
Subgroup of normal WCa
|
|
|
|
|
Model1
|
0.71(0.60to0.85)
|
reference
|
0.53(0.37to0.77)
|
0.53(0.35to0.81)
|
Model2
|
0.55(0.43to0.71)
|
reference
|
0.49(0.29to0.84)
|
0.28(0.14to0.55)
|
Subgroup of elevated WCa
|
|
|
|
|
Model1
|
0.93(0.82to1.06)
|
reference
|
0.94(0.71to1.24)
|
0.90(0.65to1.25)
|
Model2
|
0.84(0.69to1.01)
|
reference
|
0.79(0.53to1.18)
|
0.81(0.50to1.32)
|
Notes: 25(OH)D,25 hydroxy vitamin D, MetS[Modified ATP Ⅲ(2009)], Metabolic syndrome based on modified ATP Ⅲ(2009);MetS[Modified Criteria(2012) ], Metabolic syndrome based on Modified Criteria(2012); WC, Waist circumference(cm);
Model1,adjusted for age,sex;
Model2,adjusted for age, sex, race, education, marrage, physic, smoking, drinking, BMI;
a ,Metabolic syndrome is diagnosied with modified ATP Ⅲ(2009).
Table3. Multiple logistic regression for the association of individual Components of metabolic syndrome with vitamin D status
variables
|
25(OH)D[OR (95%CI)]
|
continuous
|
<20ng/ml
|
20-30ng/ml
|
≥30ng/ml
|
Elevated triglycerides
|
0.60(0.51to0.71)
|
reference
|
0.54(0.40to0.74)
|
0.38(0.25to0.56)
|
Reduced HDL cholesterol
|
0.67(0.58to0.78)
|
reference
|
0.66(0.50to0.89)
|
0.47(0.32to0.69)
|
Elevated glucose
|
0.88(0.78to0.99)
|
reference
|
0.86(0.66to1.12)
|
0.80(0.59to1.10)
|
Elevated WC
|
1.08(0.95to1.24)
|
reference
|
1.00(0.73to1.37)
|
1.04(0.72to1.51)
|
Elevated BP
|
1.19(1.02to1.39)
|
reference
|
1.15(0.82to1.62)
|
1.34(0.89to2.03)
|
Notes: Multivariate model is adjust for age, sex, race, education, marrage, physic, smoking, drinking, BMI;
25(OH)D, 25 hydroxy vitamin D, HDL, high density lipoprotein. WC, waist circumference(cm);BP, blood pressure
Table4. Multiple logistic regression for the association of individual Components of metabolic syndrome with vitamin D status after adjustment of the other MetS components
variables
|
25(OH)D[OR (95%CI)]
|
continuous
|
<20ng/ml
|
20—30ng/ml
|
≥30ng/ml
|
Elevated triglycerides
|
0.70(0.59to0.82)
|
reference
|
0.59(0.42to0.83)
|
0.46(0.30to0.71)
|
Reduced HDL cholesterol
|
0.74(0.63to0.87)
|
reference
|
0.81(0.59to1.13)
|
0.64(0.42to0.97)
|
Elevated glucose
|
0.84(0.75to0.95)
|
reference
|
0.86(0.65to1.14)
|
0.73(0.53to1.01)
|
Elevated waist circumference
|
1.09(0.94to1.25)
|
reference
|
0.96(0.70to1.33)
|
1.05(0.72to1.54)
|
Elevated blood pressure
|
1.26(1.07to1.49)
|
reference
|
1.23(0.87to1.75)
|
1.49(0.97to2.29)
|
Notes: Multivariate model is adjust for age, sex, race, education, marrage, physic, smoking, drinking, BMI, plus additionally adjusted for the rest of the individual components of the MetS;
25(OH)D, 25 hydroxy vitamin D, HDL, high density lipoprotein. WC, waist circumference(cm);BP, blood pressure
Table5. Sensitive analysis for the association of metabolic syndrome based on different diagnostic criterias with 25(OH)D status
variables
|
25(OH)D[OR (95%CI)]
|
continuous
|
<20ng/ml
|
20—30ng/ml
|
≥30ng/ml
|
Exclude people with combined diseases
|
|
|
|
|
MetS [modified ATP Ⅲ]
|
0.7(0.58to0.86)
|
reference
|
0.58(0.38to0.88)
|
0.53(0.32to0.88)
|
MetS[Modified Criteria(2012)]
|
1.14(0.94to1.38)
|
reference
|
1.00(0.64to1.57)
|
1.07(0.64to1.79)
|
Mets (CDS)
|
0.48(0.36to0.65)
|
reference
|
0.33(0.18to0.60)
|
0.37(0.19to0.73)
|
Exclude people with inadequate mobility
|
|
|
|
|
MetS [modified ATP Ⅲ]
|
0.73(0.62to0.86)
|
reference
|
0.62(0.45to0.87)
|
0.54(0.36to0.81)
|
MetS[Modified Criteria(2012)]
|
0.73(0.62to1.27)
|
reference
|
0.62(0.45to1.23)
|
0.54(0.36to1.57)
|
Mets (CDS)
|
0.62(0.51to0.76)
|
reference
|
0.5(0.34to0.73)
|
0.48(0.30to0.76)
|
Exclude people under 80 years old
|
|
|
|
|
MetS [modified ATP Ⅲ]
|
0.86(0.74to1.02)
|
reference
|
0.78(0.55to1.11)
|
0.76(0.48to1.18)
|
MetS[Modified Criteria(2012)]
|
1.06(0.89to1.26)
|
reference
|
0.90(0.60to1.35)
|
1.00(0.60to1.65)
|
Mets (CDS)
|
0.68(0.55to0.84)
|
reference
|
0.62(0.40to0.96)
|
0.54(0.31to0.96)
|
Notes: Multivariate model is adjust for age, sex,race,education,marrage,physic,smoking,drinking,BMI;