Table 6. Regression coefficients for change in log benzophenone-3 concentrations according to frequency of sunscreen use, stratified by 6-month time period (n=4412).

Frequency of sunscreen use	Exam period
	Nov-April	May-Oct
Never	ref	ref
Rarely	0.3 (0.0-0.6)	0.2 (0.0-0.5)
Sometimes	0.6 (0.3-0.8)	1.2 (0.9-1.5)
Most of the time	1.6 (1.3-2.0)	1.6 (1.3-1.9)
Always	1.9 (1.5-2.3)	2.1 (1.7-2.4)
P-trend	<0.01	<0.01
Model R2	0.25	0.23
Sunscreen R2	0.08	0.11

Adjusted for age, sex, ethnicity, BMI, education, sun avoidance

• Urinary benzophenone-3 (BP-3) is a metabolite of a common sunscreen ingredient.
• We modeled urinary BP-3 against self-reported sunscreen usage.
• We observed a positive association between sunscreen use and urinary BP-3 concentrations.
• R² was low, suggesting self-report is a valid although weak way of assessing frequency of sunscreen use.