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Table 1 Summary characteristics of studies included in the analysis of vitamin D deficiency and risk of AD

From: Vitamin D deficiency as a risk factor for dementia and Alzheimer’s disease: an updated meta-analysis

 Author, Publication year& country

Study Type

Sex

Age (Mean)

No.Patients (totle)

Follow-up duration (year)

25(OH)D (ng/ml)

OR

95% CI

Quality score

Vitamin D assessment method

Adjustment

 Karakis, 2016, US

Prospective cohort

W/M

72.4

1663

9

< 10

0.97

0.47–2.00

8

Competitive protein-binding assay and radioimmunoassay

Age, gender, smoking, HTN, DM, prevalent CVD, homocysteine, BMI, and vitamin D supplement use.

 Afzal, 2014, Denmark

Prospective cohort

W/M

58.0

4087

21

< 10 10–20

1.25 1.12

0.95–1.64 0.90–1.40

9

Not report

Age, sex, month of blood sample, smoking status, body mass index, leisure time and work-related physical activity, alcohol consumption, income level, education, baseline diabetes mellitus, hypertension, cholesterol, high-density lipoprotein cholesterol, and creatinine

 Littlejohns 2014, US

Prospective Cohort

W/M

73.6

1547

5.6

< 10 10–20

2.22 1.69

1.02–4.83 1.06–2.69

8

Liquid chromatography tandemmass spectrometry (LC-MS)

Age, season of vitamin D collection, education, sex, BMI, smoking, alcohol consumption, and depressive symptoms

 Feart, 2017, France

Prospective cohort

W/M

73.3

916

11.4

< 10 10–20

2.21 1.65

1.28–3.80 0.98–2.77

8

One-step immunoassay

Gender, education, income, depressive symptomatology, number of drugs per day, apolipoprotein E e4 allele, BMI, practice of physical exercise, DM, history of CVD and stroke, HTN, hypercholesterolemia, hypertriglyceridemia, smoking status, and Mediterranean diet score

 Buell, 2010, US

Cross-sectional

W/M

73.5

318

 

< 20

2.65

0.99–7.16

7

Radioimmunoassay (DiaSorin, Inc.,Stillwater, MN, USA) on fasting blood sample

Age, race, sex, body mass index, and education, kidney function, multivitamin use, season, diabetes, hypertension, plasma homocysteine, and ApoE allele status

 Licher, 2017, Netherlands

Prospective cohort

W/M

69.2

6087

13.3

< 20

1.10

1.00–1.19

9

Electrochemilumin-escence binding assay

Age, sex, season of blood collection, BMI, SBP, DBP, educational level, smoking, alcohol use, calcium serum levels, ethnicity, eGFR, TC, HDL, history of DM, HF, stroke, MI, depressive symptoms, outdoor activity, and APOE −4 carrier status.