Study of Use of Products and Exposure-Related Behaviors (SUPERB): study design, methods, and demographic characteristics of cohorts

Table 1 Enrollment and completion rates of Tiers I, II, and III

	Targeted enrollment; (% recruited northern, central)	Actual enrollment (northern, central)	Full data completion (northern, central)	Only partial data completion (northern, central)	Only minimal data completion (northern, central)
Tier I: year 1 only			5 survey elements	3-4 survey elements	1-2 survey elements
	n = 750	n = 655	n = 580	n = 31	n = 39
	(26%,32%)	(499, 156)	(87%,95%)	(6%,2%)	(7%,3%)
Tier I: longitudinal (years 1-3)			3 years	2 years	≤1 year
	See above	See above	n = 252	n = 182	n = 221
			(38%,41%)	(25%,37%)	(37%,22%)
Tier II: 15/18 months^a			15-18 monthly surveys	10-14 monthly surveys	1-9 monthly surveys
	n = 250	n = 250	95^b	26	129
	(77%,75%)	(186, 64)	(29%,63%)	(11%,9%)	(60%,28%)
Tier III: 8 visits over 4 seasons^b			4 collection periods^c	2-3 collection periods	1 collection period
	n = 40	n = 47	n = 40	n = 4	n = 3
	(34%,52%)	(30, 17)	(90%,76%)	(7%,12%)	(3%,12%)

^a Full completion depended upon timing of enrollment into tier 2 as it was modified from 15 to 18 months.
^b Includes participants (n = 53) who attempted to complete surveys but encountered issues with the internet survey.
^c Each collection consisted of a set-up visit and a take-down visit at the beginning and end of a week. The goal was for four collection periods across a 16 month period.

ISSN: 1476-069X