A Scottish Record Linkage Study of Risk Factors in Medical History and Dementia Outcome in Hospital Patients

Abstract

The relative risk (RR) of acquiring a hospital diagnosis of dementia was estimated in 101,104 patients (1 in 25 fraction) randomly selected from total admissions to Scottish general hospitals between 1968 and 1977. The patients were allocated to putative at-risk groups according to main diagnosis at time of index admission, and RR of dementia (ICD 9290) was contrasted between ten risk groups and a reference group. Record linkage was used to reduce admission episodes to individual cases, to link general and psychiatric Scottish Morbidity Records (SMR 1 and SMR 4), to identify subsequent admission diagnoses of dementia, and to establish person-years-at-risk for each case by linking to the Registrar General''s mortality file. For males, RR was significantly increased in the ''hypertensive'' risk group (RR 3.88:95% CI 2.18–9.89: p < 0.05) and was significantly reduced in the ''arterial disease'' risk group (RR 0.57:95% CI 0.34–0.95: p <0.05). There was a trend towards increased risk in the cerebrovascular category. For females, RR was significantly reduced in the ''cancer'' risk group (RR 0.46:95% CI 0.34–0.63: p < 0.05). There was no evidence of significant alteration in RR in a number of other possible risk groups (endocrine, head injury, CNS/NS disease, ischaemic heart disease, peptic ulcer). Morbidity registers provide access to large data sets of low reliability. No attempt was made to distinguish between Alzheimer''s disease and multi-infarct dementia cases, which limited scope for comparison with studies focused on Alzheimer''s disease. Previous reports of positive associations between head injury, thyroid disorder, and subsequent Alzheimer''s disease were not replicated.

Head injury and the risk of AD in the MIRAGE study

“…Some show that head injury has a significant or nearly significant effect on AD risk, [1][2][3][4][5][6][7][8][9] whereas others show no association. [10][11][12][13][14] Among longitudinal studies, [15][16][17][18] only one 17 reported a significantly increased risk of developing AD in persons with head injury. A reanalysis of the Rochester Epidemiology Project data suggested that head injury may reduce the time to onset of AD.…”

Cohort Profile: The Scottish Health Surveys Cohort: linkage of study participants to routinely collected records for mortality, hospital discharge, cancer and offspring birth characteristics in three nationwide studies

“…Retrospective data from 1981 until conduct of survey interview provides information on hospital diagnoses of any pre-existing morbidity. Similar linkage had previously been carried out in a randomly selected sample of individuals admitted to Scottish general hospitals in the late 1960–1970s 12 and registered users of general practices in the mid-1980s 13 Table 2Data available according to each SMR scheme Code Record type SMR00OutpatientSMR01 a General/acute inpatient/day caseSMR02MaternitySMR04 a Mental health inpatient/day caseSMR06 a Cancer registerSMR11Neonatal dischargeSMR50Geriatric (long stay)

a Available in the minimum SHeS–SMR.

Figure 1Linkage of study members of the SHeSs to hospital discharge, cancer registry and mortality records

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Big Data in Complex Systems

“…The few examples of comprehensive record linkage systems include the Oxford Record Linkage Study (Acheson 1967;Goldacre, Shiwach and Yeates 1994), that applying these techniques on birth, death and hospital data of around 350,000 individuals allowed the study of associations between certain diseases, and using longitudinal matched data enabled the analysis of occupational mortality, migration and related socio-economic factors, the Scottish Record Linkage System (Kendrick and Clarke 1993;Ryan 1994), the Rochester Epidemiology Project (Melton 1996) and the Manitoba Population Health Information System Black, Burchill and Roos 1995).…”