Table 2.

Association between the number of nevi on the back at 12 years of age and measures of sun protection during the previous summer (6 months before) and the summer 2.5 years before measurement of nevi

Summer 2.5 y before measurement
Previous summer
nRatio (95% confidence interval)*PAdjusted meannRatio (95% confidence interval)PAdjusted mean
Time spent outdoors between 11 a.m. and 2 p.m.
    Actual time1,0131.07 (1.04-1.10)<0.0019531.05 (1.03-1.08)<0.001
    Proportion of total,§1,0081.03 (1.01-1.06)0.029451.05 (1.03-1.09)<0.001
Back covered with clothing
    Some of the time5821.25 (1.15-1.37)<0.00111.15981.22 (1.11-1.33)<0.00110.9
    All of the time4351.008.93551.008.9
Use of sunscreen on the back while it was exposed
    Back covered at all times4350.81 (0.72-0.91)0.598.93550.87 (0.76-1.00)0.599.0
    ≥90% of time1781.0011.01391.0010.2
    60-89% of time1920.99 (0.87-1.14)10.91551.08 (0.93-1.26)11.1
    <60% of time2071.04 (0.91-1.19)11.42961.07 (0.93-1.22)11.0
  • * Ratio of geometric means. Adjusted for sex, southern European ethnicity, parental education, propensity to burn, hair color, inner arm skin reflectance, and study group. Time spent outdoors was adjusted for back cover and back cover, and sunscreen use was adjusted for time outdoors.

  • Adjusted geometric mean of “nevi + 1,” with values of covariates set to the distribution of the subjects included in the analysis.

  • Estimate corresponds to a doubling of the time outdoors.

  • § Proportion of the total time spent outdoors between 8 a.m. and 5 p.m.

  • P for trend, excluding category “back covered at all times.”