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Dietary fatty acids and sudden unexpected cardiac death
thesisposted on 2023-05-27, 05:22 authored by Sexton, Peter Thomas
Part 1 of this thesis is a descriptive epidemiological study of mortality from coronary heart disease (CHO) among men in Tasmania. Part 2 is an analytical epidemiological study which uses a case-control design to examine the relationship between dietary fatty acids and sudden unexpected cardiac death in Tasmanian men. Part 1: Mortality from CHO in Tasmanian men. In common with several Western industrialised countries, mortality from CHO has declined by more than 50% in Australia over the past 20 years. CHO now accounts for approximately 25% of all deaths. Analysis of data provided by the Australian Bureau of Statistics (ABS) showed that most of the decline in mortality from all causes in each of the six Australian States over the period 1972-1988 is due to a decline in mortality from CHO. In the island State of Tasmania, the rate of decline in mortality from all causes in both sexes was significantly less (p<0.01) than in the mainland Australian States, and the discrepancy was due to a slower rate of fall in mortality from CHO (p<0.01 ). It seems unlikely that these differences in mortality from CHO are due to artefact, as they were matched by parallel trends in mortality rates from all causes. Furthermore, in Tasmania, a cause of death coded to ICD 9 rubrics 410-414 (CHO) was found to have a sensitivity of 94% and a positive predictive value of 90% for fatal definite myocardial infarction or possible coronary death as defined by the World Health Organisation. Detailed analysis of mortality data for men over the period 1986 to 1989 for the three health regions of Tasmania revealed that the two northern regions of Tasmania which represent approximately 52% of the total population, accounted for 98% of the excess mortality from CHO in Tasmania compared with the national rate. Between 1986 and 1989, the Tasmanian rate for mortality from CHO was 17% higher than the Australian rate (p<0.001 ). The rate in the North-West Region of Tasmania was 38% higher than the national figure (p<0.001 ), while the rate for the Northern Region was 26% higher (p<0.001 ). The difference between mortality from CHO in the Southern Region of Tasmania and the national rate was not significant (p=0.99). There was evidence that the pattern of consumption of dietary fat in Tasmania differed from that for the rest of Australia, but the relevant data for a regional comparison of dietary habits within Tasmania were not available. Part 2: Sudden unexpected cardiac death and dietary fatty acids. A population based case-control study was undertaken to test the hypothesis that the ratio of polyunsaturated to saturated fatty acids in the diet is inversely related to the incidence of sudden unexpected cardiac death (SUCO), that is, cardiac death occurring within one hour of onset of symptoms in individuals with no previous history of CHO. Male cases of SUCO from between 1987 and 1989 (n=102) were matched by age and sex to 102 cases of first-ever acute myocardial infarction (AMI) and 204 controls drawn from electoral rolls. Data on risk factors for CHO, including a food frequency questionnaire, were collected via a structured interview conducted with the spouses of cases and controls. Forward step-wise multiple conditional logistic regression was used to examine the effect on risk of SUCO of various aspects of dietary intake of fat, the variables usually being treated as quartiles. Cigarette smoking, leisure-time physical activity, current treatment for hypertension, socio-economic status, consumption of alcohol, family history (FH) of CHO, relative body mass and history of diabetes mellitus were considered as potential confounding variables. When community controls were compared with cases of SUCD, significant odds ratios were found for the following risk factors: current smoking (0R=3.6), family history of CHO (0R=2.5), history of diabetes mellitus (0R=3.8), history of treated hypertension (0R=1.9) and dietary cholesterol greater than 21 O mg per day (0R=2.9). When community controls were compared with cases of first-ever AMI, significant odds ratios were found for family history of CHO (0R=7.1 ), current smoking (0R=6.4), some regular leisure-time physical exercise (0R=3.7) and dietary mono-unsaturated fat (0R=4.0-5.8). The present study found that dietary P:S ratio was not inversely related to the incidence of SUCD.
Rights statementIncludes bibliographical references (leaves 175-195). Thesis (Ph.D.)--University of Tasmania, 1994