Table 4.

Mean paraben concentrations in exposed and unexposed urine samples, stratified by time (hours) of exposure relative to urinary paraben concentration measurements

			Unadjusted model			Adjusted model*
Time** (hours)	Number of samples exposed	Number of samples unexposed	Exposed	Unexposed	P	Exposed	Unexposed	P
Methyl paraben (ng/ml)
<26	12	45	121.3 (58.8)	69.6 (21.6)	0.33	101 (57.5)	73.9 (20.3)	0.62
0.75–7.0	4	14	590 (473.0)	58.1 (34.5)	0.08	527 (472)	60.8 (34.3)	0.11
21.3–<26	6	24	60.9 (29.4)	67.7 (26.5)	0.51	49.2 (23.6)	77.4 (29.8)	0.16
Propyl paraben (ng/ml)
<26	12	45	20.8 (10.5)	13.0 (4.1)	0.37	16.6 (10.0)	13.9 (3.7)	0.75
0.75–7.0	4	14	160 (96.8)	11.5 (3.9)	0.01	99.9 (94.1)	13.4 (3.7)	0.10
21.3–<26	6	24	7.5 (3.8)	9.5 (4.0)	0.28	5.5 (2.6)	11.2 (3.6)	0.02
Butyl paraben (ng/ml)
<26	12	45	1.16 (0.60)	1.12 (0.47)	0.94	1.04 (0.54)	1.15 (0.47)	0.82
0.75–7.0	4	14	2.36 (2.51)	1.40 (0.55)	0.55	1.79 (2.10)	1.53 (0.40)	0.88
21.3–<26	6	24	1.00 (0.52)	1.33 (0.76)	0.50	0.76 (0.28)	1.51 (0.77)	0.07
N (%) of butyl paraben > LOD
<26	12	45	9 (75.0)	29 (64.4)	0.16	9 (75.0)	29 (64.4)	0.16
0.75–7.0	4	14	3 (75.0)	11 (78.6)	0.72	3 (75.0)	11 (78.6)	0.85
21.3–<26	6	24	5 (83.3)	18 (75.0)	0.39	5 (83.3)	18 (75.0)	0.90

LOD, limit of detection

Data are presented as the mean and standard error, accounting for multiple samples per subject using GEE models and back-transforming estimates from the log scale, or as n (%)

^*Adjusted model includes number of personal care products reported during the 24 hours prior to sample collection; the estimates presented are the mean urinary paraben concentrations for the mean number of personal care products used by all participants (9.1), those with medication use 0.75–7.0 hours (7.4), and those with medication use 21.3–<26 hours (9.3)

^**Time is defined as the number of hours elapsed between the reported medication use and the collection of the urine sample; two subjects with 2 exposed and 7 unexposed samples had an unknown time of medication use and were excluded from the stratified analysis