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Table 1 Audit trail of individuals into the MRC CFAS study

From: Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation

 

Cambridge

Gwynedd

Newcastle

Nottingham

Oxford

Total

Ascertained

3601

4654

3700

4100

4179

20234

   Died before sample date

75 (2)

32 (1)

10 (<1)

9 (<1)

18 (<1)

144 (1)

   Moved before sample date

24 (1)

10 (<1)

25 (1)

33 (1)

155 (4)

247 (1)

   Duplicates

14 (<1)

17 (<1)

0 (0)

6 (<1)

6 (<1)

43 (<1)

   Wrong area

0 (0)

0 (0)

196 (5)

0 (0)

18 (<1)

214 (1)

   DOB incorrect

9 (<1)

15 (<1)

4 (<1)

3 (<1)

3 (<1)

34 (<1)

In scope

3479 (97)

4580 (98)

3465 (94)

4049 (99)

3979 (95)

19552 (97)

   Language ineligible

0 (0)

16 (<1)

3 (<1)

27 (1)

2 (<1)

48 (<1)

   GP refusal

0 (0)

24 (1)

32 (1)

69 (2)

7 (<1)

132 (1)

   Relative

0 (0)

0 (0)

1 (<1)

0 (0)

0 (0)

1 (<1)

   Never found

14 (<1)

75 (2)

160 (5)

70 (2)

98 (2)

417 (2)

   Over sampled

0 (0)

752 (10)

67 (2)

565 (14)

19 (<1)

1403 (7)

Available

3465 (100)

3713 (81)

3202 (92)

3318 (82)

3853 (97)

17551 (90)

   Dead

190 (5)

203 (5)

188 (6)

185 (6)

260 (7)

1026 (6)

   Refused

641 (18)

807 (22)

484 (15)

521 (16)

813 (21)

3266 (19)

   Moved

33 (1)

78 (2)

6 (<1)

98 (3)

40 (1)

255 (1)

   Screened

2601 (75)

2625 (71)

2524 (79)

2514 (76)

2740 (71)

13004 (74)

  1. Numbers (percentage, calculated from previous total in bold).