Ian L. Rouse

Population‐based linkage of health records in Western Australia: development of a health services research linked database

Objectives: To Introduce the Western Australian Health Services Research Linked Database as infrastructure to support aetlologic, utilisation and outcomes research. To compare the study population, data resources, technical systems and organisational supports with international best practice in record linkage and health research.

A decade of data linkage in Western Australia: strategic design, applications and benefits of the WA data linkage system

OBJECTIVES The report describes the strategic design, steps to full implementation and outcomes achieved by the Western Australian Data Linkage System (WADLS), instigated in 1995 to link up to 40 years of data from over 30 collections for an historical population of 3.7 million. Staged development has seen its expansion, initially from a linkage key to local health data sets, to encompass links to national and local health and welfare data sets, genealogical links and spatial references for mapping applications. APPLICATIONS The WADLS has supported over 400 studies with over 250 journal publications and 35 graduate research degrees. Applications have occurred in health services utilisation and outcomes, aetiologic research, disease surveillance and needs analysis, and in methodologic research. BENEFITS Longitudinal studies have become cheaper and more complete; deletion of duplicate records and correction of data artifacts have enhanced the quality of information assets; data linkage has conserved patient privacy; community machinery necessary for organised responses to health and social problems has been exercised; and the commercial return on research infrastructure investment has exceeded 1000%. Most importantly, there have been unbiased contributions to medical knowledge and identifiable advances in population health arising from the research.

The Relationship of Blood Pressure to Diet and Lifestyle in Two Religious Populations

The association between blood pressure and a vegetarian diet was studied in relation to obesity, sex, age and lifestyle in 98 Seventh-day Adventist (SDA) lacto-ovo vegetarians, 82 SDA omnivores and 113 Mormon omnivores aged 25 to 44 years. Mean blood pressures adjusted for age, height and weight were significantly lower in SDA vegetarians than in Mormon omnivores (115.6/68.7 and 121.2/72.2, respectively, in males and 109.1/66.7 and 114.9/72.6, respectively, in females) and were not related to past or current use of alcohol, tobacco, tea and coffee, physical activity, personality or religious observance. Mean blood pressures in SDA omnivore males (121.7/71.7) were similar to those in Mormon males, while those in SDA omnivore females (109.9/67.4) were similar to SDA vegetarian females. Quetelets Index in these subgroups demonstrated the same pattern as blood pressure and may reflect, in part, the high level of physical activity in female SDA omnivores. The prevalence of mild hypertension (≥ 140 mmHg systolic or ≥ 90 mmHg diastolic) was 10 and 8.5% in Mormon and SDA omnivores, respectively, compared with 1 to 2% in SDA vegetarians. Analysis of diet records showed that vegetarians ate significantly more dietary fibre, polyunsaturated fat, magnesium and potassium and significantly less total fat, saturated fat and cholesterol than did Mormon omnivores. SDA omnivores had a dietary pattern which was less homogeneous, and which lay between those of the other groups. Which, if any, of these dietary differences were responsible for the blood pressure differences could not be determined in this study.

Effects of Alcohol Consumption on Serum Lipoprotein-Lipid and Apolipoprotein Concentrations Results from an Intervention Study in Healthy Subjects

Serum levels of cholesterol, triglyceride, cholesterol in low density lipoprotein (LDL) and in high density lipoprotein (HDL) and its major subfractions, and of apolipoproteins A-I, A-II and B were measured in 48 healthy men at the end of two 6-week periods in which they consumed normal alcohol (5.0%, v/v) or low alcohol (0.9%, v/v) beer, respectively. Other dietary and behavioural variables were kept constant. Mean levels of triglyceride, HDL cholesterol, HDL2- and HDL3 cholesterol, and apolipoproteins A-I and A-II were higher at the end of the normal compared with the low alcohol periods, and levels of LDL cholesterol were lower. Body weight was greater at the end of the normal alcohol period than at the end of the period of low alcohol but multiple regression analysis suggested that the changes in lipoprotein-lipid and apolipoprotein levels were due primarily to the change in alcohol consumption rather than concomitant changes in body weight. This study confirms an effect of alcohol on both major subfractions of HDL and on its major apolipoproteins.

Validation of linked administrative data on end‐stage renal failure: application of record linkage to a ‘clinical base population’

Objective: To evaluate the use of record linkage to monitor the occurrence of end‐stage renal failure in Western Australia in 1980–94.

Vegetarian Diet and Blood Pressure

There is now convincing evidence from epidemiological studies and randomized controlled trials that adoption of an ovo-lacto vegetarian diet leads to blood pressure reduction in both normotensive and hypertensive subjects. This effect appears to be independent of both dietary sodium and weight loss but additive to effects of weight reduction. Long-term adherence to a vegetarian diet is associated with less of a rise of blood pressure with age and a decreased prevalence of hypertension. The nutrients responsible for these effects have not been clearly identified and the mechanisms involved are unknown. Resolution of these questions is needed to enable more widespread adoption of dietary changes which may reduce the prevalence of hypertension, reduce antihypertensive drug dependence and by effects on blood pressure and blood lipids ameliorate the natural history of hypertensive cardiovascular disease.

Plasma calcium and cortisol as predisposing factors to alcohol related blood pressure elevation.

Mechanisms by which alcohol consumption might cause hypertension were examined in 30 pairs of healthy drinking (greater than 275 g ethanol per week) and teetotal men closely matched for age and obesity. Both systolic and diastolic blood pressures were significantly higher in the drinkers. Plasma calcium levels correlated with diastolic blood pressures (r = 0.51, P = 0.004) in drinkers only. After adjusting for plasma albumin, diastolic pressures increased by 6.9 mmHg for each 0.1 mM increment of plasma calcium. It is proposed that regular alcohol consumption predisposes to hypertension by facilitating calcium accumulation in cells involved in blood pressure regulation. In the combined population of drinkers and teetotallers plasma cortisol correlated positively with diastolic pressure (r = 0.35, P = 0.012) and negatively with plasma potassium (r = -0.38, P = 0.006); this suggests a role for the pituitary/adrenal axis as a significant determinant of blood pressure differences between healthy subjects.

PLASMA NORADRENALINE AND ITS RELATIONSHIP TO PLASMA OESTRADIOL IN NORMAL WOMEN DURING THE MENSTRUAL CYCLE

1. In order to investigate a possible relationship beween sympatho‐adrenal neuronal activity and the endocrine changes during the menstrual cycle, free and sulphate‐conjugated plasma catecholamines and oestradiol were measured under carefully controlled conditions in 26 normal menstruating women.

Relationships between age, body weight, physical fitness and sex-hormone-binding globulin capacity

The associations between sex-hormone-binding globulin capacity (SHBG), age, body mass index (BMI), and physical fitness have been studied in 34 men and 36 women. Multivariate analysis was used to look for independent associations with SHBG. The data indicate that when controlled for a number of other factors SHBG levels are related, in men but not in women, to age (positively, p less than 0.001) and BMI (negatively, p less than 0.001).

Comparison of diets supplemented with fish oil or olive oil on plasma lipoproteins in insulin-dependent diabetics

This study was designed to compare changes in high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)-cholesterol in normolipidaemic male insulin-dependent diabetics (IDD) following dietary supplementation with either the fish oil concentrate Max EPA or olive oil. The contribution of the small quantity of cholesterol in Max EPA to these changes was also examined. Twenty-seven subjects were matched in groups of three and randomly allocated to one of three treatment groups of nine subjects each. Subjects were given 15 1-g capsules of oil daily for 3 weeks, consisting of either Max EPA, olive oil, or olive oil to which was added the same amount of cholesterol as contained in Max EPA, respectively. There was a significant increase in eicosapentaenoic acid, and a decrease in arachidonic acid, in the platelet membrane phospholipids of subjects taking Max EPA. In this group, there was an approximately 30% increase in serum HDL2-cholesterol (0.59 +/- 0.07 to 0.77 +/- 0.11 mmol/L, mean +/- SEM; P less than .01) and a corresponding decrease in HDL3-cholesterol (0.79 +/- 0.03 to 0.71 +/- 0.03 mmol/L; P less than .05). Although total and LDL-cholesterol concentrations were also higher after Max EPA, the changes were not significant. Triglycerides were significantly decreased by Max EPA. There were no significant changes in lipids in the groups given olive oil. These results show that compared with olive oil, dietary supplementation with Max EPA substantially increases HDL2-cholesterol in insulin-dependent diabetics. This is most likely due to a selective effect of omega 3 fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)