Family History of Melanoma and Lifetime Patterns of Daytime Hours Spent Outdoors in Melanoma-prone Families

Longer daytime hours spent outdoors reflect higher ultraviolet radiation exposure, which is a modifiable risk factor of melanoma. Among individuals of melanoma-prone families, we sought to describe lifetime patterns for hours spent outdoors, and to investigate whether having an affected family member with melanoma from an older generation was associated with patterning. Methods: Information on hours spent outdoors on weekdays, weekends, and holidays beginning at age 10 was obtained from individuals from melanoma-prone families. We determined time-weighted average hours outdoors for warmer months, colder months, and the entire year. K-means for longitudinal data was used to identify lifetime patterns. We created a variable to indicate whether there was an existing melanoma in a prior generation of an individual's family. Multinomial logistic regression models were used to examine the association between family history of melanoma and lifetime patterns of daytime hours spent outdoors, adjusting for covariates. Results: We analyzed 2540 individuals from 669 families ascertained across 15 countries, and four lifetime patterns were identified. Three patterns began with moderate hours that (B) decreased slowly (n = 1014); (C) decreased sharply until age 20 and then remained low (n = 572); or (D) increased at age 20 and remained high (n = 173). One pattern, (A) began with few hours that decreased at age 20 then remained very low (n = 781). Compared to individuals with the high (D) pattern, individuals with an existing melanoma in a prior family generation were more likely to have the low (A) pattern (OR = 1.92, 95% CI: 1.34–2.76), the moderate and slowly decreasing (B) pattern (OR = 1.72, 95% CI: 1.15–2.57), or the sharply decreasing (C) pattern (OR = 2.01, 95% CI: 1.40–2.87). Similar associations were observed separately in warmer and colder months. Examining lifetime patterns of hours spent outdoors during holidays, we noticed a stronger relationship with family history of melanoma in warmer months than in colder months. Conclusions: As expected, the diagnosis of a melanoma in a prior generation may impact family members' awareness of UVR exposure leading to reduced daytime hours spent outdoors.

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