Dorothy Mackerras

An Australian Aboriginal birth cohort: a unique resource for a life course study of an Indigenous population. A study protocol

BackgroundThe global rise of Type 2 diabetes and its complications has drawn attention to the burden of non-communicable diseases on populations undergoing epidemiological transition. The life course approach of a birth cohort has the potential to increase our understanding of the development of these chronic diseases. In 1987 we sought to establish an Australian Indigenous birth cohort to be used as a resource for descriptive and analytical studies with particular attention on non-communicable diseases. The focus of this report is the methodology of recruiting and following-up an Aboriginal birth cohort of mobile subjects belonging to diverse cultural and language groups living in a large sparsely populated area in the Top End of the Northern Territory of Australia.MethodsA prospective longitudinal study of Aboriginal singletons born at the Royal Darwin Hospital 1987–1990, with second wave cross-sectional follow-up examination of subjects 1998–2001 in over 70 different locations. A multiphase protocol was used to locate and collect data on 686 subjects with different approaches for urban and rural children. Manual chart audits, faxes to remote communities, death registries and a full time subject locator with past experience of Aboriginal communities were all used.DiscussionThe successful recruitment of 686 Indigenous subjects followed up 14 years later with vital status determined for 95% of subjects and examination of 86% shows an Indigenous birth cohort can be established in an environment with geographic, cultural and climatic challenges. The high rates of recruitment and follow up indicate there were effective strategies of follow-up in a supportive population.

Dietary Patterns Identified Using Factor Analysis and Prostate Cancer Risk: A Case Control Study in Western Australia

PURPOSE Dietary patterns offer an alternative method for analyzing dietary intakes that take into account the whole diet. We investigated empirical dietary patterns and prostate cancer risk in Western Australia (WA) using a population-based case-control study. METHODS Incident prostate cancer cases were identified via the WA Cancer Registry. Controls were sourced from the WA electoral roll, frequency matched on age. A food frequency questionnaire (FFQ) estimated usual dietary intake from 10 years earlier. Factor analysis identified dietary patterns in FFQ data. Effects of independent dietary patterns on prostate cancer risk were examined using unconditional logistic regression, adjusting for potential confounders. RESULTS A total of 546 cases and 447 controls provided data. Three distinct dietary patterns were identified, which we labeled vegetable, Western, and health-conscious. An increased risk for prostate cancer was observed with the Western pattern, which consisted of high intakes of red and processed meats, fried fish, hamburgers, chips, high-fat milk, and white bread. Men in the highest quartile for Western pattern score had an odds ratio of 1.82 (95% confidence interval 1.15-2.87, trend p = 0.02). Results were similar for aggressive cases and attenuated for non-aggressive cancers. CONCLUSIONS A western style diet may lead to increased risks for prostate cancer, especially aggressive prostate cancer.

Fruit, vegetable, vitamin A intakes, and prostate cancer risk

Prostate cancer risk was examined in relation to intakes of fruit, vegetables, β-carotene and retinol. Subjects were a cohort of 1985 men previously to asbestos who participated in a cancer prevention programme of β-carotene and retinol supplements that commenced in July 1990. Diet was assessed at entry to the programme. Ninety-seven cases of prostate cancer were identified during follow-up until the end of 2004. A decreased prostate cancer risk was observed with increasing intakes of vitamin C-rich vegetables, including bell peppers and broccoli. Fruit, other vegetables and vitamin A intakes did not appear to be strong factors in the development of prostate cancer in this study.

Comparison of an Australian food-frequency questionnaire with diet records: implications for nutrition surveillance

OBJECTIVES To compare a widely used Australian food-frequency questionnaire (FFQ) with diet records and consider the results in relation to its use in nutrition surveillance. DESIGN Inter-method reliability study. SETTING A randomised trial in subjects with past asbestos exposure. SUBJECTS Seventy-two adults living in Western Australia. METHODS A semi-quantitative FFQ developed by the Commonwealth Scientific Industrial Research Organisation in South Australia was administered after the completion of four 7-day diet records (DRs). RESULTS Mean agreement between methods was not significantly different from 100% for many nutrients, but the limits of agreement indicated that, at the individual level, the FFQ over- or underestimated the DR by at least 50%. Mean agreement between methods decreased significantly with increasing intakes for the majority of nutrients. Pearsons correlation coefficients were less informative indicators of agreement compared with the limits of agreement. CONCLUSIONS These results indicate poor agreement between the FFQ and DR when estimating absolute intakes. Therefore, comparing intakes collected using this FFQ with specific cut-off points such as Recommended Dietary Intakes for nutrition surveillance may lead to seriously flawed conclusions about population intakes.

Birthweight changes in the pilot phase of the Strong Women Strong Babies Strong Culture Program in the Northern Territory

Objective : The Strong Women Strong Babies Strong Culture Program had specific goals to increase infant birthweights by earlier attendance for antenatal care and improved maternal weight status. Starting in August 1993, Aboriginal women in three pilot communities worked with pregnant women in a program that emphasised both traditional practices and Western medicine.

Agreement between a brief food frequency questionnaire and diet records using two statistical methods

OBJECTIVE To compare intra- and inter-method reliability of a semi-quantitative food frequency questionnaire (FFQ) designed specifically to measure beta carotene (BC) and retinol intake, using two methods - the limits of agreement (LOA) and the correlation coefficient. DESIGN A cross-sectional study of dietary intake. SETTING A randomized trial of vitamin A supplements in 2769 subjects with past asbestos exposure. SUBJECTS Data from 57 men and 26 women, aged 28-72 years, living in Western Australia. METHODS The FFQ was administered at baseline (FFQ1) and repeated 1 year later (FFQ2). Four 1-week diet records (DRs) were completed during the year. RESULTS Mean agreement between FFQ2 and FFQ1 was 120% for BC and 98% for retinol. LOA were 47-306% and 21-459%, respectively. Mean agreement between FFQ2 and the DR was 149% for BC and 63% for retinol; LOA were 50-447% and 11-349%, respectively. Mean agreement and LOA varied across energy intakes. Between the DR and FFQ2, correlation coefficients were 0.36 for BC and 0.51 for retinol. These varied considerably across age, gender and energy intakes and were not in accordance with limits of agreement findings. CONCLUSION Although correlation coefficients were positive and significant, there was less than ideal intra-method and inter-method reliability shown by the limits of agreement method. Bias was uneven across the range of intakes, the LOA were wide and, compared with the DR, the FFQ significantly over-estimated BC and under-estimated retinol. This shows the limitations of calculating correlation coefficients alone, for assessing reliability and validity.

24-Hour national dietary survey data : how do we interpret them most effectively?

OBJECTIVE To illustrate the effect of common mistakes when using 24-hour national dietary survey data to estimate the prevalence of inadequate nutrient intakes. DESIGN Raw data on nutrient intake from the Australian 1995 National Nutrition Survey were adjusted for within-person variance using standard techniques and corrected for underreporting using the criteria of Goldberg et al. The distributions for six nutrients were compared with current dietary reference values from the UK, USA and Australia. SETTING A national sample of the Australian population with a 61.4% response rate. RESULTS Adjusting for within-person variance reduced the range of nutrient intakes to 66-80% of the raw data range and the proportion with intakes below the estimated average requirement (EAR) by up to 20%. Excluding underreporters further reduced the proportion below the EAR by up to 10%. Using the dietary reference values from different countries also resulted in some markedly different estimates. For example, the prevalence of low folate intakes ranged from < 1 to 92% for adult women depending on the reference used. Except for vitamin A and protein, the prevalence of low intakes was invariably higher for women than for men. CONCLUSIONS Estimates of the prevalence of low nutrient intakes based on raw 24-hour survey data are invariably misleading. However, even after adjustment for within-person variance and underreporting, estimates of the prevalence of low nutrient intakes may still be misleading unless interpreted in the light of the reference criteria used and supported by relevant biochemical and physiological measures of nutritional status.

Australian Aboriginal Birth Cohort study: follow-up processes at 20 years

BackgroundIn 1987, a prospective study of an Australian Aboriginal Birth Cohort was established focusing on the relationships of fetal and childhood growth with the risk of chronic adult disease. However as the study is being conducted in a highly marginalized population it is also an important resource for cross-sectional descriptive and analytical studies. The aim of this paper is to describe the processes of the third follow up which was conducted 20 years after recruitment at birth.MethodsProgressive steps in a multiphase protocol were used for tracing, with modifications for the expected rural or urban location of the participants.ResultsOf the original 686 cohort participants recruited 68 were untraced and 27 were known to have died. Of the 591 available for examination 122 were not examined; 11 of these were refusals and the remainder were not seen for logistical reasons relating to inclement weather, mobility of participants and single participants living in very remote locations.ConclusionThe high retention rate of this follow-up 20 years after birth recruitment is a testament to the development of successful multiphase protocols aimed at overcoming the challenges of tracing a cohort over a widespread remote area and also to the perseverance of the study personnel. We also interpret the high retention rate as a reflection of the good will of the wider Aboriginal community towards this study and that researchers interactions with the community were positive. The continued follow-up of this life course study now seems feasible and there are plans to trace and reexamine the cohort at age 25 years.

Dietary patterns and surgically treated benign prostatic hyperplasia: a case control study in Western Australia

To investigate dietary patterns and food intake as risk factors for surgically treated benign prostatic hyperplasia (BPH), as few risk factors have been established for BPH and recently there has been some interest in a role for diet in the development of BPH.

Does the store-turnover method still provide a useful guide to food intakes in Aboriginal communities?

Objective: To consider the application of the store‐turnover method as a guide to assess food intake in remote Aboriginal communities.