Background: The incidence of cutaneous malignant melanoma, which is 86% attributable to UV radiation exposure, has been increasing steadily over the past five decades in predominantly fair-skinned populations. Although sun-protection campaigns in Scotland have increased awareness and sun-protective behaviour, their impact on melanoma incidence remains unclear.

Objectives: We conducted a retrospective population-based cohort study to examine changes in the epidemiology of melanoma in Scotland during the past five decades – to evaluate the impact of historical sun-protection campaigns and to inform the future direction of sun-protection strategies.

Methods: Anonymised individual level data for patients diagnosed with cutaneous malignant melanoma during 1971-2020 were obtained from the Scottish Cancer Registry and Intelligence Service. Average annual incidence rates (AAIR) per 100,000 population were calculated by three age categories (0-34, 35-64, 65+ years), gender and anatomical site during the 10 five-year time periods (1971-75 to 2016-20).

Results: During the 50-year period, a total of 34,997 cases of melanoma (43.9% males, 56.1% females) were registered in Scotland. The average annual number of cases increased from 53/year in 1971-75 to 674/year in 2016-20 in males (+1172%), and from 108/year in 1971-75 to 675/year in 2016-20 in females (+525%). In young males (aged 0-34 years) there was steady increase in AAIR from 1971-75 to 1996-2000, from 0.7-3.3/100,000, followed by a decline to 2.0/100,000 in 2016-20. Similarly in young females, there was steady increase in AAIR from 1971-75 to 2006-10, from 1.0-7.2/100,000, followed by a decline to 5.5/100,000 in 2016-20.
 
In the middle age group (35-64 years), there was a steady/linear increasing trend in the AAIR during the study period – the rates in males increased by +676% (from 3.0/100,000 in 1971-75 to 23.1/100,000 in 2016-20), and in females by +382% (from 5.7/100,000 in 1971-75 to 27.5/100,000 in 2016-20). Similarly in the older age group (65+ years), the AAIR in males increased by 1151% (from 7.0/100,000 in 1971-75 to 87.9/100,000 in 2016-20), and in females by 463% (from 9.6/100,000 in 1971-75 to 54.0/100,000 in 2016-20). The magnitude of increase in middle/older ages was about twice as much in males as compared to females, and highest in the older age group, suggesting a cohort effect. As for the anatomical site, the largest increase was observed for melanoma of the upper limb (+2247% in males, +1115% in females), followed by melanoma of the trunk (+1794% in males, +951% in females).

Conclusion: These findings suggest that the incidence of melanoma among young people in Scotland is declining, whereas it continues to increase significantly in older population, indicating substantial historical UV exposure and a strong cohort effect. It appears that long-term sun?protection campaigns targeted at children/adolescents/parents may be having a positive impact. The steeper increase in incidence in males is consistent with their relatively greater sun exposure and poor sun-protective behaviour. Available evidence suggests that the enormous increase in the melanoma of the upper limb and trunk, is most likely due to increasing trend in intermittent high intensity recreational UV radiation exposure (e.g. sunbathing, holidaying in places with strong sunlight, indoor tanning).