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Table 3 Study-level characteristics distribution, overall and comparison across risk factors

From: Epidemiologic studies of modifiable factors associated with cognition and dementia: systematic review and meta-analysis

 

Overall

EDU

SMOK

ALCO

PA

CAFF

ANTIOX

HCY

N-FA

P*

N = 247

N = 52

N = 36

N = 30

N = 28

N = 18

N = 27

N = 33

N = 23

Year, Mean (SD)

2004.5

(5.1)

2001.3

(6.3)

2003.6

(5.2)

2004.5

(4.5)

2006.7

(3.6)

2007.7

(4.5)

2003.8

(3.8)

2006.2

(3.1)

2006.9

(4.0)

<0.001

Country, N (%)

                   

US

98

(39.7)

16

(30.8)

12

(33.3)

15

(50.0)

17

(63.0)

3

(16.7)

17

(63.0)

13

(39.4)

5

(21.7)

0.020

Europe

104

(42.1)

22

(42.3)

18

(50.0)

9

(30.0)

8

(28.6)

10

(55.6)

8

(29.6)

14

(42.4)

15

(65.2)

 

Other

45

(18.2)

14

(26.9)

6

(16.7)

6

(20.0)

3

(10.7)

5

(27.8)

2

(7.4)

6

(18.2)

3

(13.00

 

Age group, N (%)

                   

Excludes < 65y

147

(59.5)

31

(59.6)

17

(47.2)

13

(43.3)

24

(85.7)

12

(66.7)

20

(74.1)

16

(48.5)

14

(60.9)

0.012

Includes < 65y

100

(40.5)

21

(40.4)

19

(52.8)

17

(56.7)

4

(14.3)

6

(33.3)

7

(25.9)

17

(51.5)

9

(39.1)

 

Sex, N (%)

                   

Both

208

(84.2)

47

(90.4)

28

(77.8)

28

(93.4)

19

(67.9)

16

(88.9)

22

(81.5)

28

(84.8)

20

(87.0)

0.12

Men only

26

(10.5)

3

(5.8)

8

(22.2)

1

(3.3)

5

(17.9)

2

(11.1)

2

(7.4)

3

(9.1)

2

(8.7)

 

Women only

13

(5.3)

2

(3.8)

0

(0.0)

1

(3.3)

4

(14.3)

0

(0.0)

3

(11.1)

2

(6.1)

1

(4.3)

 

Study design, N (%)

                   

Cross-sectional

80

(32.4)

25

(48.1)

7

(19.4)

12

(40.0)

4

(14.3)

7

(38.9)

6

(22.2)

14

(42.4)

5

(21.7)

0.012

Cohort

167

(67.6)

27

(51.9)

29

(80.6)

18

(60.0)

24

(85.7)

11

(61.1)

21

(77.8)

19

(57.6)

18

(78.3)

 

Sample size, Mean (SD)

3,561

(5,128)

4,345

(6,066)

4,745

(6,859)

4,745

(6,808)

3,322

(3,927)

2,408

(2,385)

3,643

(4,191)

1,074

(769)

3,061

(3,389)

0.05

Cognitive outcome count, N (%)

                   

1

179

(72.5)

34

(65.4)

26

(86.7)

26

(86.7)

20

(71.4)

14

(77.8)

22

(81.5)

21

(63.6)

15

(65.2)

0.77

2

60

(24.3)

15

(28.8)

4

(13.3)

4

(13.3)

7

(25.0)

3

(16.7)

4

(14.8)

10

(30.3)

8

(34.8)

 

3

5

(2.0)

2

(3.9)

0

(0.0)

0

(0.0)

1

(3.6)

1

(5.6)

0

(0.0)

1

(3.0)

0

(0.0)

 

4

2

(1.2)

1

(1.9)

0

(0.0)

0

(0.0)

0

(0.0)

0

(0.0)

1

(3.7)

1

(3.0)

0

(0.0)

 

Cognitive outcome type, N (%)

                  

0.042

AD/dementia/impairment

114

(46.2)

26

(50.0)

20

(55.6)

6

(20.0)

16

(57.1)

5

(27.8)

15

(55.6)

15

(45.5)

11

(47.8)

 

Cognitive function/decline

126

(51.0)

25

(48.1)

16

(44.4)

24

(80.0)

10

(35.7)

11

(61.1)

12

(44.4)

17

(51.5)

11

(47.8)

 

Both

7

(2.8)

1

(1.9)

0

(0.0)

0

(0.0)

2

(7.1)

2

(11.1)

0

(0.0)

1

(3.0)

1

(4.4)

 

Study finding, N(%)

                  

0.004

Against hypothesis

5

(2.0)

1

(1.9)

1

(2.8)

2

(6.7)

1

(3.6)

0

(0.0)

0

(0.0)

0

(0.0)

0

(0.0)

 

Null

45

(18.2)

4

(7.7)

11

(30.6)

4

(13.3)

0

(0.0)

5

(27.8)

9

(33.3)

6

(18.2)

6

(26.1)

 

Positive

152

(61.5)

39

(75.0)

18

(50.0)

17

(56.7)

25

(89.3)

7

(38.9)

11

(40.7)

23

(69.7)

12

(52.2)

 

Partially positive (outcomes/exposures)

21

(8.5)

6

(11.5)

2

(5.6)

2

(6.7)

0

(0.0)

3

(16.7)

2

(7.4)

1

(3.0)

1

(4.3)

 

Partially positive (sub-groups)

24

(9.7)

2

(7.7)

4

(11.1)

5

(16.7)

2

(7.1)

3

(16.7)

5

(27.8)

3

(9.1)

4

(17.4)

 
  1. *P-value for difference across risk/protective factors was obtained from one-way ANOVA test when variable is continuous and χ 2 test when variable is categorical.