Time spent in the sun and the risk of developing non-Hodgkin lymphoma: a Canadian cohort study.

PURPOSE: The objective was to explore the relationship of sun behavior patterns with the risk of developing non-Hodgkin lymphoma (NHL). METHODS: Sun behavior information from Alberta's Tomorrow Project, CARTaGENE, and Ontario Health Study were utilized. The relationship between time in the sun during summer months and risk of NHL was assessed using Cox proportional hazard models with age as the time scale and adjustment for confounders. Cohorts were analyzed separately and hazard ratios (HR) pooled with random effects meta-analysis. Joint effects of time in the sun and use of sun protection were examined. Patterns of exposure were explored via combinations of weekday and weekend time in the sun. RESULTS: During an average follow-up of 7.6 years, 205 NHL cases occurred among study participants (n = 79,803). Compared to < 30 min daily in the sun, we observed HRs of 0.84 (95% CI 0.55-1.28) for 30-59 min, 0.63 (95% CI 0.40-0.98) for 1-2 h, and 0.91 (95% CI 0.61-1.36) for > 2 h. There was suggestive evidence that > 2 h was protective against NHL with use of sun protection, but not without it. Compared to < 30 min daily, moderate exposure (30 min to 2 h on weekdays or weekend) was associated with a lower risk of NHL (HR 0.63, 95% CI 0.43-0.92), while intermittent (< 30 min on weekdays and > 2 h on weekends) and chronic (> 2 h daily) were not. CONCLUSION: This study provides evidence of a protective effect of moderate time spent in the sun on NHL risk.

Combinations of modifiable lifestyle behaviours in relation to colorectal cancer risk in Alberta's Tomorrow Project.

The objective of this study was to identify distinct clusters of individuals that exhibit unique patterns of modifiable lifestyle-related behaviours and to determine how these patterns are associated with the risk of developing colorectal cancer (CRC). The study consisted of 26,460 participants and 267 CRC cases from Alberta's Tomorrow Project. Exploratory latent class analysis of risk behaviours (obesity, physical inactivity, meat consumption, smoking, alcohol consumption, and fruit and vegetable consumption) and Cox proportional hazard models were utilized. Seven unique behavioural groups were identified, where the risk of CRC was 2.34 to 2.87 times greater for high risk groups compared to the low risk group. Sex-specific models identified higher risk groups among men (Hazard Ratios [HRs]: 3.15 to 3.89) than among women (HRs: 1.99 to 2.19). Targeting groups defined by clustering of behaviours could potentially lead to more effective prevention of CRC on a population level.

Solar Ultraviolet Radiation and Breast Cancer Risk: A Systematic Review and Meta-Analysis.

BACKGROUND: A protective relationship has been hypothesized between exposure to solar ultraviolet radiation (UVR) and the development of breast cancer. OBJECTIVE: The objective of this study was to conduct a systematic literature review and meta-analysis of studies examining the association of exposure to solar UVR and breast cancer risk. METHODS: We searched Medline, EMBASE, and Web of Science for all studies investigating exposure to solar UVR and breast cancer risk. Separate analyses were performed using estimates of time spent in the sun, and ambient UVR. Associations were estimated using DerSimonian and Laird random-effect models. Heterogeneity was investigated through subgroup analyses and I2 statistics. RESULTS: Fourteen studies were included in the review and 13 in the meta-analysis, with the majority (n=8) conducted in North America. We observed a decreased risk of breast cancer for individuals spending ≥1h/d in the sun during summer months over a lifetime or usual adulthood compared with <1h/d [pooled relative risk (RR)=0.84; 95% CI: 0.77, 0.91]. Spending ≥2h/d in the sun had a similar protective effect as 1 to <2h/d when compared with <1h/d (RR=0.83; 95% CI: 0.75, 0.93 vs. 0.83; 95% CI: 0.78, 0.89). Exposure during adolescence was suggestive of a lower risk of breast cancer than exposure later in life (≥45 years of age) (RR=0.83; 95% CI: 0.71, 0.98 vs. 0.97; 95% CI: 0.85, 1.11). Ambient UVR was not associated with the risk of breast cancer (RR=1.00; 95% CI: 0.93, 1.09). DISCUSSION: To our knowledge, this was the first meta-analysis to estimate the risk of developing breast cancer associated with time spent in the sun. The results suggest that obtaining greater than an hour a day in the sun during the summer months could decrease the risk of developing breast cancer. https://doi.org/10.1289/EHP4861.

Indoor tanning and the risk of developing non-cutaneous cancers: a systematic review and meta-analysis.

PURPOSE: Despite a strong association between indoor tanning and the risk of cutaneous cancers, the relationship between indoor tanning and non-cutaneous cancers is unknown. Our objective was to estimate the association of indoor tanning with developing non-cutaneous cancers. METHODS: We conducted a systematic literature review and meta-analysis of the association between indoor tanning and non-cutaneous cancer sites. Associations were estimated using random effects models. Heterogeneity was investigated through subgroup analyses and the Q-test and I2 statistics. RESULTS: From 15 identified studies, 33 effect estimates for 12 cancer sites were included in the review. Adjustment for sun exposure was a significant source of heterogeneity in the association of indoor tanning and non-cutaneous cancer risk (meta-regression p = 0.0043). When restricting to studies that adjusted for solar ultraviolet radiation (7 studies and 19 effect estimates) a potential increased risk was observed among ever users of indoor tanning devices with the risk of hematologic malignancies (pooled relative risk = 1.11; 95% CI 0.96-1.28), with differing effects observed by hematologic types and subtypes of non-Hodgkin lymphoma. No association was observed among solid non-cutaneous cancers (pooled relative risk = 0.98; 95% CI 0.94-1.19). Neither study design nor geographical region was significant sources of heterogeneity in these associations. CONCLUSION: When controlling for sun exposure, indoor tanning does not protect against solid non-cutaneous cancers and may increase the risk of some hematologic malignancies. Given the well-established relationship with skin cancer and potential relationship with hematologic malignancies, efforts to reduce the use of indoor tanning devices should continue.