Evaluation of non-response bias in a cohort study of World Trade Center terrorist attack survivors

BMC Research Notes

Table 1 Study population characteristics and their associations with dropping-out of wave 3

	Wave 3 participants	Wave 3 non-participants	Likelihood of dropping out of wave 3
	(N = 42,934) %	(N = 24,736) %	AOR ^a	95% CI
Sex
Male	61.1	58.8	1.1***	1.1, 1.2
Female	38.9	41.2	reference	reference
Age at wave 1 interview, year
<=24	3.5	6.7	2.2***	1.9, 2.5
25 - 44	46.2	56.0	1.8***	1.7, 2.0
45 - 64	45.9	32.7	1.0	0.9, 1.1
> = 65	4.3	4.7	reference	reference
Race
Non-Hispanic black	10.2	15.0	1.8***	1.7, 1.9
Hispanic	11.6	16.2	1.5***	1.4, 1.6
Asian	5.8	9.4	16***	1.4, 1.7
Other-multi-racial	3.5	5.4	1.3***	1.2, 1.5
Non-Hispanic white	68.8	54.0	reference	reference
Total household Income in 2002, $
<25,000	9.1	15.2	1.3***	1.3, 1.4
25,000- < 50,000	19.7	25.1	1.1**	1.1, 1.2
50,000- < 75,000	21.9	19.8	0.9	0.9, 1.0
75,000- < 150,000	37.1	29.0	0.9**	0.9, 1.0
> = 150,000	12.3	10.9	reference	reference
Education
High school and below	22.6	29.2	1.4***	1.3, 1.5
College	57.0	54.6	1.2***	1.1, 1.2
Post-graduate	20.4	16.2	reference	reference
Study recruitment source
List-identified	26.3	36.7	1.7***	1.7, 1.8
Self-identified	73.7	63.4	reference	reference
Eligibility group
Lower Manhattan resident	14.0	20.0	1.6***	1.5, 1.7
Lower Manhattan area worker	34.0	33.1	1.2***	1.1, 1.2
Passersby on 9/11	5.1	6.1	1.3***	1.2, 1.4
Other^b	0.2	0.2	0.8	0.5, 1.2
Rescue/recovery worker	46.6	40.7	reference	reference

Abbreviations: AOR, adjusted odds ratio; CI, confidence interval.
*P < 0.05; **P < 0.01; ***P < 0.0001.
^aAdjusted for all factors listed in this table and in Table 2.
^bStudents and school staff in public schools south of Canal Street on 9/11/2001.

ISSN: 1756-0500