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. 2017 Feb 21;19(2):e46. doi: 10.2196/jmir.6417

Table 1.

Demographic characteristics comparable across all stages.

Stage of study N Age (years) Gender (male)


Mean (SD) Range t (df) P n/N (%) χ21 P
Screened 11,530 41.1 (14.6) 16-90 –9.86 (3492) <.001 6164/11,461 (53.78)


Noneligible 6565 43.7 (16.1) 16-90

3633/6514 (55.77) 30.7 <.001

Eligible 4186 39.2 (13.2) 18-65

2103/4181 (50.30)

Point of consent


3.23 (1842) .001

0.3 .59

Refused 2278 40.2 (13.9) 18-65

1142/2274 (50.22)


Randomized 1139 38.3 (12.5) 18-65

560/1139 (49.17)

Intervention period


–0.73 (561) .47
7.2 .009

Completers 536 38.5 (12.7) 18-65

261/536 (48.7)


Dropouts 27 40.3 (13.0) 21-63

6/27 (22.2)

Follow-up period


–1.28 (36) .21
10.1 .002

Completers 1088 38.3 (12.5) 18-65

545/1088 (50.09)


Withdrawals 35 41.1 (12.6) 18-63

8/35 (22.9)

Postal survey


–8.14 (1120) <.001
18.5 <.001

Completers 534 41.5 (12.6) 18-65

227/534 (41.0)


Dropouts 589 35.5 (11.8) 18-65

326/589 (59.0)