Can routinely collected hospital admission data be used to study temporal morbidity and mortality trends in maintenance renal replacement patients? Analyses from the Oxford Record Linkage Study and all England Hospital Episode Statistics, 1965 2011

Maintenance dialysis programmes for end-stage renal disease (ESRD) began in the United Kingdom in the 1960s. Until the 1980s, renal replacement therapy (RRT, i.e., dialysis or kidney transplantation) was restricted to ESRD patients who were considered the most economically active and those with diabetes or other comorbidities were often not referred or treated. This contrasts with the situation 50 years later when the median age of patients starting maintenance RRT is 65 years and diabetes is the leading cause of ESRD. Examining long-term temporal mortality trends helps describe past and current serious health risks. Their interpretation is difficult in RRT populations as comparisons between treated ESRD and other populations need to take account of the substantial secular changes in the prevalence of comorbid illnesses which influence both mortality and the likelihood of receiving RRT. To date, no large study has standardized mortality rates in treated ESRD and general population cohorts to the same comorbidity as well as age/sex structure. Therefore, although data from ESRD registries in the United States 1977-2007, Europe 1998-2007, Australasia 1992-2005,and UK 2002-2011 have all shown modest improvements in mortality for people with treated ESRD, it is unclear whether the magnitude of this change is comparable to those observed in the general population during the same period. The Oxford Record Linkage Study (ORLS) was established in 1963 and recorded information about all hospital inpatient admissions in Oxfordshire and the surrounding counties. Hospital Episode Statistics (HES) succeeded ORLS and established nationwide coverage from 1998. Mortality trends among new maintenance RRT patients and a set of general population controls, extracted from these two datasets were performed. Novel approaches ensured that both cohorts could be corrected for changes in prior comorbidity over time and the effects of transplantation, and stratified analyses in patients with and without diabetes could be performed.   Key aims of thesis 1) Derive and validate a cohort of end-stage renal disease (ESRD) patients exclusively from anonymised, individually-linked prospectively collected hospital inpatients datasets 2) Analyse the temporal trends of age, sex and comorbidity adjusted mortality rates in the ESRD cohort 3) Concurrently derive a comparative general population to provide an opportunity to compare trends between the ESRD and general populations 4) Demonstrate other uses of routinely collected hospital inpatients datasets in renal epidemiology