Table 2.

Hazard ratios (HR) and 95% confidence intervals (CI) of first primary basal cell carcinoma by quintile of average lifetime summer ambient temperature, ultraviolet radiation, and time outdoors lagged by 20 years, in the U.S. Radiologic Technologists study

		Range	Median	No. cases	HR	95% CI	p-trend
Temperature^1,2
	Q1	46.3–69.0	67.5	646	1.00
	Q2	69.0–71.2	70.2	664	1.08	0.97–1.20
	Q3	71.2–73.3	72.2	689	1.07	0.96–1.19
	Q4	73.3–76.6	74.7	771	1.18	1.06–1.31
	Q5	76.6–93.6	79.4	786	1.07	0.95–1.20	0.09
Ultraviolet radiation³
	Q1	75.8–175.6	170.0	600	1.00
	Q2	175.6–183.7	179.2	654	1.06	0.94–1.20
	Q3	183.7–196.2	187.7	663	1.01	0.88–1.15
	Q4	196.2–220.5	206.7	744	1.24	1.09–1.42
	Q5	220.5–312.2	236.7	895	1.54	1.35–1.75	<0.0001
Time outdoors⁴
	Q1	0–10.8	7.8	641	1.00
	Q2	10.8–16.3	13.9	677	1.18	1.06–1.31
	Q3	16.3–21.2	18.6	670	1.22	1.09–1.36
	Q4	21.2–26.9	24.0	659	1.11	0.99–1.23
	Q5	26.9–38.5	30.9	793	1.12	1.00–1.24	0.18

HR adjusted for sex, BMI (<25;25-<30; ≥30 kg/m²; missing), eye color (categories), average lifetime summer time outdoors (quintiles), average liftime summer UVR (continuous), with the baseline hazard stratified on birth cohort (5-year categories). P-trend values based on categories treated as continuous ordinal values (quintiles).

Fahrenheit scale.

Erythemal exposure, (J/m²); HRs adjusted for covariates as in temperature model but including temperature (quintiles). P-trend values based on categories treated as continuous ordinal values (quintiles).

⁴

Hours/week; case count does not sum to 3,556 because some participants did not report time outdoors (missing, n=116 cases; 2691 non-cases). HRs adjusted for covariates as in temperature model but including temperature (quintiles). P-trend values based on categories treated as continuous ordinal values (quintiles).