The Association of Smoking and Socioeconomic Status on Cutaneous Melanoma

A Population-based, Data-linkage, Case-control Study

J.A.G. Gibson; T.D. Dobbs; R. Griffiths; J. Song; A. Akbari; S. Whitaker; A. Watkins; S.M. Langan; H.A. Hutchings; R.A. Lyons; I.S. Whitaker

Disclosures

The British Journal of Dermatology. 2020;182(5):1136-1147. 

In This Article

Abstract and Introduction

Abstract

Background: Previous studies have identified an inverse association between melanoma and smoking; however, data from population-based studies are scarce.

Objectives: To determine the association between smoking and socioeconomic (SES) on the risk of development of melanoma. Furthermore, we sought to determine the implications of smoking and SES on survival.

Methods: We conducted a population-based case–control study. Cases were identified from the Welsh Cancer Intelligence and Surveillance Unit (WCISU) during 2000–2015 and controls from the general population. Smoking and SES were obtained from data linkage with other national databases. The association of smoking status and SES on the incidence of melanoma were assessed using binary logistic regression. Multivariate survival analysis was performed on a melanoma cohort using a Cox proportional hazard model using survival as the outcome.

Results: During 2000–2015, 9636 patients developed melanoma. Smoking data were obtained for 7124 (73·9%) of these patients. There were 26 408 controls identified from the general population. Smoking was inversely associated with melanoma incidence [odds ratio (OR) 0·70, 95% confidence interval (CI) 0·65–0·76]. Smoking was associated with an increased overall mortality [hazard ratio (HR) 1·30, 95% CI 1·09–1·55], but not associated with melanoma-specific mortality. Patients with higher SES had an increased association with melanoma incidence (OR 1·58, 95% CI 1·44–1·73). Higher SES was associated with an increased chance of both overall (HR 0·67, 95% CI 0·56–0·81) and disease-specific survival (HR 0·69, 95% CI 0·53–0·90).

Conclusions: Our study has demonstrated that smoking appeared to be associated with reduced incidence of melanoma. Although smoking increases overall mortality, no association was observed with melanoma-specific mortality. Further work is required to determine if there is a biological mechanism underlying this relationship or an alternative explanation, such as survival bias.

Introduction

Although there is a wealth of knowledge on the association of melanoma with risk factors such as ultraviolet light exposure, skin type and genetics,[1] the relationship between tobacco smoke and melanoma is less clear. Tobacco smoke is a type 1 carcinogen, associated with 18 types of cancer.[2] Song et al.[3] reported a moderate inverse association between melanoma and smoking in a meta-analysis of two cohort studies. This association was observed in both ex-smokers and current smokers in men, but not women. A larger meta-analysis, including 23 studies, reported a similar inverse association.[4] Both papers reported significant limitations, notably publication bias because of selective reporting in the published studies. Furthermore, confounding variables were not included in the analysis.

A recent, prospective cohort study has further explored the association. After adjusting for potential confounding factors, no association was observed between current smoking and melanoma [odds ratio (OR) 1·01, 95% confidence interval (CI) 0·64–1·61].[5] Although the study addressed the aforementioned limitations by adjusting for confounding factors, the study was significantly underpowered; only a small proportion of the cohort developed melanoma and the average follow-up duration was short (3·5 years).

The relationship between socioeconomic status and melanoma, on the other hand, is well established in the literature, with research dating back to the 1980s.[6,7] Those in higher income or higher educational groups are at an increased risk of developing melanoma, attributed to greater exposure to lifestyle factors, such as sun holidays and tanning bed use.[8] However, once diagnosed, those with a lower socioeconomic status have a worse prognosis, a finding seen across multiple jurisdictions with different healthcare systems.[8] Understanding and addressing this worsened prognosis is therefore a clear public health priority.[9–11]

In this paper we describe the largest study investigating the association of smoking and melanoma published to date. We have used the power of routinely collected data to overcome limitations of previous studies and investigate the prognostic implications of smoking in this patient cohort. Furthermore, we sought to investigate the association of socioeconomic status on the incidence and survival of melanoma.

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