Skin cancer prevention specialists should attempt to reduce ultraviolet radiation exposure (UVR) among outdoor workers, as pointed out in a recent review.1 To address this need, Project SUNWISE, a randomized controlled sun safety intervention trial with Southern Californian United States Postal Service letter carriers, was conducted from 2001 through 2004. The intervention consisted of providing free sunscreen, free wide-brim hats, a series of 6 brief onsite educational sessions, and sun safety prompts. The primary outcome measures were validated questionnaire items that asked participants how often they had used specific sun protection strategies over the past 5 workdays while delivering mail.2, 3 They were administered at baseline and 3, 12, 24, and 36 months post-baseline. The 5 response options ranged from “never” to “always”; we considered “always” as “consistent use” in analyses. At the 2-year follow-up evaluation, participants at the intervention postal stations had significantly higher rates of consistent sunscreen use and wide-brim hat use than those at control stations.2 Details about the study procedures and sample characteristics have been published previously.2 Immediately following the 2-year evaluation, control station participants received the free items and 3 of the education sessions (i.e., introduction and protections strategies, sun safety for eyes, and recap/encouragement to maintain sun safety practices). At the intervention stations, we continued to provide free sunscreen during that year. This paper describes the behavioral outcomes at the 3-year follow-up evaluation.
Evaluation cohort retention rates (of those completing questionnaires) from the 2- to 3- year follow-ups were 93.2% (927/994) for the intervention group and 94.4% (1130/1196) for the control group. The trends over 3 years in two key outcomes—consistent use of sunscreen and wide-brim hats--were analyzed using generalized linear mixed models treating 3 months, 1 year, 2 years, and 3 years as a set of repeated measures on each postal worker. In addition, we adjusted for postal workers nested within post offices within a multi-level model; the intraclass correlation coefficients for sunscreen and hats were .015 and .067, respectively. All analyses were adjusted for the baseline level of the corresponding outcome variable. For each analysis, we tested 1) the time by condition interaction, to determine if the intervention effect remained constant over time, and 2) the condition main effect. Consistent sunscreen use levels for intervention participants at the 2- and 3- year follow-ups were 39.2% and 38.3%, respectively, and for control participants, they were 26.3% and 34.3%, respectively. Wide-brim hat levels for intervention participants during these periods were 40.0% and 43.8%, respectively, and for control participants, they were 22.3% and 33.0%, respectively. Results of the analyses for each of these outcomes showed significant condition by time interaction effects (ps<0.0001), indicating that the differences between the conditions were changing over time. The table shows these patterns. For both behaviors, the change in the odds ratios from year 2 to year 3 is not due to a drop among intervention participants but rather to an increase among control group participants. We are encouraged that intervention effects were maintained at least one year after the program ended, and that once the control participants received the intervention, their consistent use of sun protection increased substantially.
Table.
Results of generalized linear mixed-model analyses a: Patterns of odds ratios over three years of follow-up
| Sunscreen | Wide-Brim Hat | |||
|---|---|---|---|---|
| Follow-up | OR b | 95% CI | OR c | 95% CI |
| 3 months | 2.69 | 2.13 – 3.39 | 3.13 | 2.43 – 4.03 |
| 1 year | 2.06 | 1.64 – 2.58 | 2.40 | 1.87 – 3.09 |
| 2 years | 1.96 | 1.54 – 2.48 | 2.64 | 2.03 – 3.43 |
| 3 years | 1.08 | 0.85 – 1.36 | 1.44 | 1.12 – 1.85 |
OR, odds ratio; CI, confidence interval
All models adjusted for baseline level of the outcome variable and postal station clustering.
Odds ratio shows the odds of always using sunscreen in the intervention group compared with the control group.
Odds ratio shows the odds of always using wide-brim hats in the intervention group compared with the control group.
Acknowledgment
We thank the following individuals for their scientific contributions to this study: Laura Eckhardt, Sam Oh, Gabriel Galindo, Cynthia Balderrama, and April Achter. We appreciate the valuable contributions to this project’s success from our contacts at the United States Postal Service (USPS) in Southern California and the National Association of Letter Carriers and the participation in the evaluation by USPS letter carriers. We acknowledge Debra Rubio for assistance in manuscript preparation.
Funding/Support: This study was supported by grants from the National Institutes of Health, National Cancer Institute (grant numbers R01CA085980, R01CA085980S1, R01CA085980S2, and K05100051).
Role of the Sponsors: The sponsors had no role in the design and conduct of the study; in the collection, analysis, and interpretation of data; or in the preparation, review, or approval of the manuscript.
Footnotes
Author Contributions: Dr. Mayer designed the study, helped interpret the data, and wrote the majority of the paper. Dr. Slymen helped design the study, analyzed the data, and participated in writing the paper. Drs. Elder, Sallis, Eichenfield, and Weinstock and Ms. Clapp helped design the study and participated in writing the paper. Ms. Pichon participated in data gathering and paper writing. All authors have approved of the final version of the manuscript.
Financial Disclosure: Dr. Weinstock has served as a consultant to sunscreen companies.
The other authors have no conflicts of interest to declare.
References
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