Socioeconomic inequalities in lung and upper aero-digestive tract cancer incidence in Scotland

HV Social pathology. Social and public welfare;RA0421 Public health. Hygiene. Preventive Medicine;RC0254 Neoplasms. Tumors. Oncology (including Cancer)

Sharpe, Katharine H. ; Conway, David I.

University:University of Glasgow

Department:School of Medicine, Dentistry & Nursing

关键词: socioeconomic inequalities, poverty, deprivation, cancer incidence, lung, head and neck,oesophageal, tumour, malignancy, neoplasm, social determinant.;   

Others  :  http://theses.gla.ac.uk/8887/1/2018sharpephd.pdf

来源: University of Glasgow

【 摘 要 】

Socioeconomic inequality in cancer risk and incidence burden has received limitedattention compared to genetic and behavioural risk factors. Where they have beenstudied, the temporal relationship between socioeconomic factors and cancer riskhas been under explored due to the mainly cross-sectional nature of mostresearch. Moreover, the inter-relationships of the multiple measures ofsocioeconomic status and, in particular, area and individual measures and theirinteraction with risk behaviours have also had limited attention. The overarchingaim of this thesis was to investigate socioeconomic inequalities in the risk of lungand upper aero-digestive tract cancers and the relationship between this risk andsocioeconomic status, area and individual based measures of socioeconomiccircumstances, and behaviours such as smoking, alcohol consumption, diet andexercise.To understand and quantify the relative contribution by age, sex and tumoursubtype to the socioeconomic inequalities of all cancer risk, a descriptiveepidemiological study of cancer incidence in Scotland (2000-07) was undertaken.Age standardised rates per 100,000 population were calculated by directstandardisation to the European standard. A linear regression model was used tocalculate the Slope Index of Inequality (SII) and Relative Index of Inequality (RII)which were employed to rank tumour and subtype contribution to all cancer risksocioeconomic inequalities by age for each sex for lung and upper aero-digestivetract (UADT) cancers separately. There were 216,305 cases excluding nonmelanomaskin cancer (all cancer) comprising 37,274 lung, 8,216 head and neckand 6,534 oesophageal cancers classified into anatomical or morphologicalsubtypes. Socioeconomic circumstances were measured using the Scottish Index ofMultiple Deprivation (SIMD). Analyses were partitioned by five-year age group andsex. RII was adapted to rank the contribution of each tumour type to all cancersocioeconomic inequalities and to examine subtype by age and sex simultaneously.The rank was defined as the proportion of all cancer socioeconomic inequality.All cancer socioeconomic inequality was greater for males than females (RII=0.366;female RII=0.279). The combination of lung and UADT socioeconomic inequalitiescontributed 91% and 81% respectively to all cancer socioeconomic inequality. Forboth sexes lung and UADT subtypes showed significant socioeconomic inequalities(P<0.001) except oesophageal adenocarcinoma in males (P=0.193); for females,socioeconomic inequality was borderline significant (P=0.048). Although RII rankdiffered by sex, all lung and larynx subtypes contributed the most to all cancersocioeconomic inequality with RII rank for oral cavity, oesophagus–squamous celland oropharynx following. For males 40-44 years old, socioeconomic inequalitiesincreased abruptly peaking at 55-59 years. For females, socioeconomic inequalitiesgradually peaked 10 years later. In both sexes, the socioeconomic inequalities peakage preceded age of peak incidence. This study showed that socioeconomicinequalities in lung and UADT cancers vary greatly by age, tumour subtype and sex;these variations were likely to largely reflect differences between the sexes in riskbehaviours which vary by birth cohort and are socioeconomically patterned.Longitudinal data enabled exploration of the temporal relationship betweensocioeconomic status and cancer incidence. An investigation of several individualand a single area-based measure of socioeconomic circumstances was undertakenin the second study of this thesis. The effect of country of birth, marital status,one area socioeconomic circumstances measure (Carstairs) and five individualsocioeconomic variables (economic activity, education, occupational social class,car ownership, household tenure) on the risk associated with lung, UADT and allcancer combined (excluding non-melanoma skin cancer) were explored. A linkeddataset using the Scottish Longitudinal Study and Scottish Cancer Registry wascreated to follow 203,658 cohort members aged 15+ years from 1991-2006.Relative risks (RR) were calculated using Poisson regression models by sex offsetfor person-years of follow-up. There were 21,832 first primary tumours (including3,505 lung and 1,206 UADT cancers). Regardless of cancer, economic inactivity(versus activity) was associated with increased risk (male: RR 1.14 95% CI 1.10,1.18; female: RR 1.06 95% CI 1.02, 1.11). For lung cancer, area deprivationremained significant after full adjustment suggesting that the area deprivationcannot be fully explained by individual variables. Not having a qualification (versusdegree) was associated with increased lung cancer risk; likewise for UADT cancerrisk (females only). Occupational social class associations were most pronouncedand elevated for UADT risk. No car access (versus ownership) was associated withincreased risk (excluding all cancer risk for males). Renting accommodation (versushome ownership) was associated with increased lung cancer risk, UADT cancer riskfor males only and all cancer risk for females only. Regardless of cancer group,elevated risk was associated with no education and living in deprived areas. Thisstudy demonstrated that different and independent socioeconomic variables wereinversely associated (greater incidence with lower socioeconomic circumstances)with different cancer risks in both sexes; no one socioeconomic variable had adominant risk association or captured all aspects of socioeconomic circumstancesor the full life-course. The association of multiple socioeconomic variables waslikely to reflect the complexity and multifaceted nature of low socioeconomiccircumstances as well as the various roles of these dimensions over the life-course.A final study investigated the role of behaviours (smoking, alcohol, diet andexercise) on the association of low socioeconomic circumstances with all cancerrisk and lung and upper aero-digestive tract cancers combined (LUADT). TheScottish Cancer Registry and Scottish Health Survey data were linked to create apopulation study (1995-2011). There were 42,983 adults over 16 years old whowere followed for 3,750,611 person-years. There were 2,130 first primary cancersdiagnosed including 453 LUADT cancers. Poisson regression models, minimallyadjusted by age and sex, were developed to estimate the risk association betweenfive individual socioeconomic variables (economic activity, highest qualification,occupational social class, car ownership and housing tenure), one area-basedsocioeconomic indicator (SIMD) and all cancer and LUADT cancer. A furthersocioeconomic indicator was developed to reflect multiple low socioeconomiccircumstances. This was defined as the count, at the individual participant level,of socioeconomic variables in the highest risk category. A similar multiple high riskbehaviour derived variable, defined as the count of highest risk category for thefollowing variables: current smoking status, units of alcohol consumed in a week,daily fruit and vegetable consumption and exercise sessions per week, was alsocalculated at the individual participant level. The minimally adjusted Poissonmodels were successively adjusted for behaviours (smoking, alcohol, diet andexercise) to establish any remaining contribution to cancer risk not explained bybehaviour. Multiple low socioeconomic circumstances were very stronglyassociated with increased risk for both cancer groups. For all cancer risk, theelevated risk was nearly fully attenuated for all categories of multiple lowsocioeconomic circumstances when adjusted for smoking only. For LUADT cancerand in the minimally adjusted model, the risk increased in a dose-responsemanner. The risk associated with LUADT cancer for study participants in thehighest category of multiple low socioeconomic circumstances was more thanthree-times greater when compared to their affluent counterparts (RR 3.35 95% CI2.26, 4.97); this elevated risk remained at 86% compared to those with nosocioeconomic disadvantage, even after full adjustment for smoking, alcohol, dietand exercise behaviours. When looking at single socioeconomic status (SES)indicators, only those who rented accommodation from a local authority remainedat a 50% increased risk of LUADT cancer even after adjustment for all thebehaviours (RR 1.50 95% CI 1.05, 2.16). This study demonstrated that smoking is amajor inequality issue and a significant cancer risk which is socially patterned.Further analytical research is required to fully understand the pathways andmechanisms between socioeconomic circumstance and lung and upper aerodigestivecancer risk. This thesis suggests that when monitoring socioeconomicinequalities and cancer risk, it is less effective to focus on all cancer as a groupgiven the mix of diseases resulting from very different aetiological processes, someassociated with high SES and others with low SES. It also suggests that bothindividual and area measures of SES are valid measures and are required to capturethe multi-dimensional nature of SES as well as the life-course andintergenerational implications of SES. In addition to this “multi-dimensional”attribute to SES, it is essential to consider multiple low social circumstancesoccurring simultaneously and therefore compounding vulnerability to cancer risk.Behaviours, particularly smoking and alcohol, explained much of the elevated lungand upper aero-digestive tract cancer risk for individual SES indicators. Clearly, inthis context, smoking is a major inequality issue and a significant cancer risk.This thesis provides useful insights for raising the issue of inequalities in cancer,for advocacy and for building policy and interventions to tackle inequalities incancer incidence. Policies need to focus on more broadly upstream causes. Traditionally, these policies have been focused on downstream behaviours (e.g.public space smoking ban and alcohol minimum pricing), but upstream policies thattake on the fundamental political decisions regarding the distribution of income,wealth and power are required at both Westminster and Holyrood and beyond.