A record linkage to examine the influence of poor mental health on breast screening uptake
Early detection is vital in the fight to reduce the morbidity and mortality associated with breast cancer and the gold-standard method of achieving this is through routine screening of the at-risk population. Currently in the United Kingdom (U.K), women aged between 50 and 70 are routinely invited through the National Health Service Breast Screening Programme (NHSBSP) to participate in elective mammography once every three years. However, screening uptake rates are suboptimal and vary widely, and this has been identified as a central factor contributing to avoidable cancer deaths. One potentially significant factor which may contribute to these gradients in screening uptake is poor mental health. Compared to the general population, individuals with a mental illness have a significantly reduced life expectancy, suffering increased morbidity and mortality from cardiovascular disease, respiratory disease, diabetes, and cancer. A number of reviews have already identified inequities in the provision of healthcare to patients with mental illness who have cancer, but it remains unclear whether this finding extends to routine breast cancer screening in the U.K. This study represents the first of its kind to examine the impact of poor mental health, and of physical disabilities, on attendance at routine breast screening in Northern Ireland. The first objective of this thesis was to identify the socio-demographic determinants of breast screening uptake in the three years following the 2011 Census, and to compare this with previously published results from the 2001 Census. Population attributable fractions were then calculated for each of the significant predictors of breast screening uptake to assess the overall contribution of socio-demographic factors to non-attendance at breast cancer screening. The second aim of the thesis was to investigate the impact of self-reported poor mental health on breast screening uptake, and the extent to which this explained previously determined socio-economic and urban/rural gradients in screening uptake. A second indicator of poor mental health, in the form of psychotropic prescribing information, was then employed to examine the impact of taking different types of psychotropic medication on breast screening uptake, and subsequently, whether the uptake of antidepressants or anxiolytic medication increased following screening invitation or attendance at screening. The final aim of the study was to investigate the impact of various types of physical disability on attendance at breast screening, and the role that poor mental health plays in any of the observed associations. In order to answer these research questions, information from three independent datasets were linked to produce one large, de-identified research dataset. Breast screening records were obtained from the Quality Assurance Reference Centre (QARC). These were then linked to psychotropic prescribing information from the Enhanced Prescribing Database (EPD), held by the Business Services Organisation (BSO), and subsequently to the Northern Ireland Longitudinal Study (NILS) which is maintained by the Northern Ireland Statistics and Research Agency (NISRA). This linkage procedure was facilitated by the inclusion of the Health and Care Number, a unique identifier which is present on all National Health Service records for individuals registered with a General Practitioner, NHS optician, or NHS dentist in Northern Ireland. Gradients in breast screening uptake were evident across a number of sociodemographic attributes and these do not appear to have reduced in the last decade. In particular, this piece of analysis revealed significantly lower breast screening uptake rates for those who had never been married (OR 0.73: 0.68 – 0.79), those who were renting socially (OR 0.65: 0.61 – 0.70), and those who had no cars in the household (OR 0.64: 0.59 – 0.69). General health was also an important determinant of attendance at breast screening, with those reporting bad or very bad health 33% (OR 0.67:0.60 – 0.74) and 46% (OR 0.54: 0.46 – 0.62), respectively, less likely to attend for screening. Disparities in breast screening uptake were also evident for women residing within the Belfast Metropolitan Area compared to those residing in the rest of Northern Ireland (OR 0.76: 0.73 – 0.80). Women with self-reported poor mental health were 23% less likely to attend screening compared to their counterparts who did not report poor mental health (OR 0.77: 0.73 – 0.82), but this did not explain the previously determined gradients in screening uptake by socio-economic status, marital status, or urban/rural residence. The employment of a subsequent indicator of poor mental health in the form of psychotropic medication utilisation provided further evidence of a disparity in screening uptake for women with poor mental health, in which the use of any form of psychotropic medication in the three months prior to screening invite was associated with a 15% reduction in the odds of attending screening (OR 0.85: 0.81 – 0.88). Further analyses indicated that breast screening uptake varied according to the type of psychotropic medication utilised - although the use of anxiolytics (OR 0.61: 0.57 – 0.66) , antipsychotics (OR 0.63: 0.56 – 0.70), and hypnotics (OR 0.68: 0.63 – 0.72) were associated with significant reductions in the odds of attending screening, the association with antidepressants was of borderline significance (OR 0.90: 0.85 – 0.94). Inequity in screening access was also evident for women with disabilities. Women with any disability were 7% less likely to attend for breast screening (OR 0.93: 0.89 – 0.8). Further analyses indicated that the magnitude and significance of the relationship varied by the type of disability examined. Significantly reduced attendance at screening was observed for women with long-term pain or discomfort (OR 0.95: 0.90 – 0.99), mobility or dexterity difficulties (OR 0.84: 0.80 - 0.88), frequent periods of confusion or memory loss (OR 0.78: 0.69 – 0.88), and shortness of breath or difficulty breathing (OR 0.87: 0.82 - 0.92). The presence of poor mental health only explained a minimal degree of the observed reduction in breast screening uptake for women with disabilities. This thesis provides novel evidence of the existence of disparities in breast screening uptake for women with poor mental health and women with disabilities in Northern Ireland. With increasing rates of poor mental health and disability in Northern Ireland, this research has great translational potential and could be utilised by policy makers to help guide the implementation of strategies to overcome these barriers to accessing breast screening. This would not only help ensure equal access for all individuals, but it would contribute to increased participation in the breast screening programme and improve the subsequent reduction in morbidity and mortality associated with breast cancer.
NILS, mental illness, disability, record linkage, breast screening
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