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Biomedical subjects

C S Guest

Publications and source records attributed to C S Guest.

At least 19 recordsLinked to original sources
PubMed2003

Deep vein thrombosis and air travel: record linkage study.

OBJECTIVE: To investigate the time relations between long haul air travel and venous thromboembolism. DESIGN: Record linkage study using the case crossover approach. SETTING: Western Australia. PARTICIPANTS: 5408 patients admitted to hospital with venous thromboembolism and matched with data for arrivals of international flights during 1981-99. RESULTS: The risk of venous thromboembolism is increased for only two weeks after a long haul flight; 46 Australian citizens and 200 non-Australian citizens had an episode of venous thromboembolism during this so called hazard period. The relative risk during this period for Australian citizens was 4.17 (95% confidence interval, 2.94 to 5.40), with 76% of cases (n = 35) attributable to the preceding flight. A "healthy traveller" effect was observed, particularly for Australian citizens. CONCLUSIONS: The annual risk of venous thromboembolism is increased by 12% if one long haul flight is taken yearly. The average risk of death from flight related venous thromboembolism is small compared with that from motor vehicle crashes and injuries at work. The individual risk of death from flight related venous thromboembolism for people with certain pre-existing medical conditions is, however, likely to be greater than the average risk of 1 per 2 million for passengers arriving from a flight. Airlines and health authorities should continue to advise passengers on how to minimise risk.

Adolescent↗
PubMed1997

A co-twin study of the effect of calcium supplementation on bone density during adolescence.

The effect of calcium supplementation on bone mineral density (BMD) was evaluated in female twin pairs aged 10-17 years with a mean age of 14 years. Forty-two twin pairs (22 monozygotic, 20 dizygotic; (including one monozygotic pair from a set of triplets) completed at least 6 months of the intervention: 37 pairs to 12 months and 28 pairs to 18 months. BMD was measured by dual-energy X-ray absorptiometry (DXA). In a double-blind manner, one twin in each pair was randomly assigned to receive daily a 1000 mg effervescent calcium tablet (Sandocal 1000), and the other a placebo tablet similar in taste and appearance to the calcium supplement but containing no calcium. Compliance (at least 80% tablets consumed), as measured by tablet count, was 85% in the placebo group and 83% in the calcium group over the 18 months of the study, on average increasing dietary calcium to over 1600 mg/day. There was no within-pair difference in the change in height or weight. When the effect of calcium supplementation on BMD was compared with placebo at approximately 6, 12 and 18 months, it was found that there was a 0.015 +/- 0.007 g/ cm2 greater increase in BMD (1.62 +/- 0.84%) at the spine in those on calcium after 18 months. At the end of the first 6 months there was a significant within-pair difference of 1.53 +/- 0.56% at the spine and 1.27 +/- 0.50% at the hip. However, there were no significant differences in the changes in BMD after the initial effect over the first 6 months. Therefore, we found an increase in BMD at the spine with calcium supplementation in females with a mean age of 14 years. The greatest effect was seen in the first 6 months; thereafter the difference was maintained, but there was no accelerated increase in BMD associated with calcium supplementation. The continuance of the intervention until the attainment of peak bone mass and follow-up after cessation of calcium supplementation will be important in clarifying the optimal timing for increased dietary calcium and the sustained, long-term effects of this intervention.

Adolescent↗
PubMed1996

Abatement of tropospheric ozone: effects of strategies to improve air quality on public health and other sectors.

The National Health and Medical Research Council's air quality goal for ozone in the troposphere (near the earth's surface) is 0.12 parts per million (ppm), averaged over one hour, similar to the United States standard, but less stringent than the guideline for Europe. We aimed to identify the environmental, economic and social changes that would be associated with changing the goal. Methods included literature review, economic assessments and group interviews. The group to benefit from lower exposures may include outdoor workers, school children and people not in regular day-time work indoors, because ozone is most prevalent during the daylight hours of the warmer months. A lower level could improve the yield of some crops. The causes and effects of tropospheric ozone are not appreciated except among groups with relevant commercial, industrial or scientific experience. However, the consultations identified frustration about the social problems caused by dependence on private motor vehicles. Short-term costs of compliance with a more stringent goal would fall principally on the users of transport. The value of the benefits was enough for many to support making the ozone goal more stringent, but those who required a demonstration of financial benefit (even including savings of health care costs) did not support any change to the goal. Based primarily on averted detriment to health, we recommend the more stringent level of 0.08 ppm (one-hour average) as the goal for the year 2005 in Australia and elsewhere. The addition of a goal with longer averaging time is also proposed.

Air Pollutants↗
PubMed1995

Determinants of bone mass in 10- to 26-year-old females: a twin study.

This cross-sectional twin study aimed to quantify the roles of constitutional and lifestyle factors on bone mass in adolescent and young adult women. Areal bone density (BMD) at the lumbar spine, femoral neck, Ward's triangle, and total hip, total body bone mineral content (BMC), and lean mass and fat mass were measured using dual energy X-ray absorptiometry (DXA) in 215 female volunteer twin pairs (122 monozygotic [MZ], 93 dizygotic [DZ]) aged 10 to 26 years. Height, weight, menarchial history, dietary calcium intake, physical activity, current tobacco use, and alcohol consumption were determined by questionnaire. Mean BMD increased with age to around 16 years, when it reached a plateau. Within-pair differences in BMD at the lumbar spine (expressed as a percentage of the pair mean BMD) were univariately associated with pair differences in menarchial status (14 +/- 3%), height (0.7 +/- 0.1% per cm), weight (0.4 +/- 0.1% per kg), lean mass (1.0 +/- 0.1% per kg), and fat mass (0.5 +/- 0.1% per kg). Only menarchial status, height, and lean mass, however, were independent predictors. At the proximal femoral sites, within-pair BMD differences were associated with within-pair lean mass differences (1.0 to 1.1 +/- 0.2%/kg), and no other factor was significant. The same conclusions applied to within-pair differences in BMD/height. Total body BMC was independently associated with menarchial status, height, lean mass, and fat mass; the effects of the latter two variables were stronger in pairs both premenarchial. After adjusting for constitutional factors, no lifestyle factor was independently predictive. By reducing collinearity, the cotwin method clearly identified that lean mass, not fat mass, was the major independent determinant of bone mass at the hip, both pre- and postmenarche.

Absorptiometry, Photon↗
PubMed1995

Knowledge of glaucoma, and its relationship to self-care practices, in a population sample.

OBJECTIVE: To determine the level of knowledge of glaucoma in a population-based sample, and its relationship to self-care practices. DESIGN AND SUBJECTS: A cluster random sample of the Melbourne population 40 years of age and older was interviewed. One thousand seven hundred and eleven residents living in five randomly selected Melbourne metropolitan suburbs, each consisting of two adjacent census collector districts. MEASURES: Questions were asked concerning respondents' awareness, knowledge and description of the disease. Respondents were also asked the year of their last visit to their eye health care provider. RESULTS: Seventy per cent of the sample had heard of glaucoma. However, only 22% provided a description that demonstrated a reasonable understanding of the disease. A lack of awareness and knowledge of glaucoma appeared to be negatively related to self-care practices. CONCLUSION: Serious deficiencies in the basic knowledge of glaucoma in the community was demonstrated. This has significant public health implications as only a small percentage of the at-risk population may present themselves for assessment and treatment. Informing the community about glaucoma is an important step in promoting preventative ophthalmic care and reducing visual impairment and blindness.

Adult↗
PubMed1994

Comparison between Fastpac and conventional Humphrey perimetry.

As part of the Melbourne Visual Impairment Project, a substudy was performed to determine the efficacy of the newly released Fastpac program for the Humphrey Field Analyser. A comparison was performed of the Fastpac and conventional full threshold 24-2 fields obtained in 39 eyes of 36 participants. Also a comparison study was performed of the standard and non-standard 80-point screening tests to the standard 24-2 full threshold test in 23 eyes of 23 participants. In the full threshold comparison there was 100% agreement between the two with Fastpac being 32% to 39% faster than standard. In the 80-point screening test comparison, non-standard was no faster than standard. Sensitivities were 17/17 (1.0) for non-standard and 15/18 (0.83) for standard, as compared with the standard 24-2 full threshold test. Fastpac software offers accurate screening and threshold testing in less time than the standard algorithm.

Algorithms↗
PubMed1994

Blood pressure, lipids and other risk factors for cardiovascular disease in Aborigines and persons of European descent of southeastern Australia.

Based on a survey in two country towns of southeastern Australia, cardiovascular risk-factor prevalence data from Aborigines and persons of European descent are presented. The mean diastolic blood pressure in 123 Aboriginal males was 83.2 mmHg, compared with 79.2 mmHg in 272 European males (P = 0.005). In 178 Aboriginal females, mean diastolic pressure was 79.2 mmHg, compared with 76.3 mmHg in 281 European females (P = 0.006). Mean plasma total cholesterol was higher in Europeans (both males and females: 5.7 mmol/L) than in Aborigines (in males 5.2 and females 5.0 mmol/L) (male comparison, P = 0.02, female comparison, P < 0.001). The prevalence in participants aged 25 to 64 years of at least one major risk factor (diastolic blood pressure 95 mmHg or higher, plasma cholesterol 6.5 mmol/L or higher, or smoking more than one cigarette daily) was higher in both these samples of Aborigines (94 per cent in males, 89 per cent in females) and Europeans (70 per cent in males, 59 per cent in females) than in the 1989 urban sample of the National Heart Foundation (47 per cent in males, 36 per cent in females). Multivariate analyses showed statistically significant independent contributions of body mass index and the variable 'ethnicity' (unidentified genetic and environmental differences between the groups) to blood pressure and other risk factors. The higher cardiovascular mortality of Aborigines may be explained partly by the higher prevalence of risk factors in this group compared with other Australians. Further, the risk-factor profile may be worse among rural compared with urban Europeans.

Adult↗
PubMed1994

Cost-effectiveness of recruitment methods in a population-based epidemiological study: the Melbourne Visual Impairment Project.

The cost-effectiveness of five recruitment methods was evaluated to determine the best method of encouraging eligible persons to participate in the Melbourne Visual Impairment Project (a population-based epidemiological study). The evaluation was divided into two phases. Phase 1 included one of two types of initial contact, by direct personal contact or by telephone. Phase 2 involved recruiting residents after an attempt had been made by either the telephone or the doorstep approach, and included a second attempt by a field interviewer, subsequent attempts by senior field staff, and finally, financial incentives. The cost-effectiveness of each method was determined by dividing the approach's cost by the effectiveness ratio. We identified 269 eligible households with 356 eligible residents. An 89 per cent response rate was achieved at the examination centre, comprising 61 per cent from Phase 1 and 28 per cent from Phase 2. Although both recruitment methods in Phase 1 were equally cost-effective, there was a significant difference in the effectiveness of each method in actually recruiting residents. The doorstep method was more costly per attender but was far more effective at 76 per cent recruitment than the telephone method at 47 per cent (P < 0.001). We have demonstrated a practical two-stage approach (the doorstep method in Phase 1 and follow-up strategies in Phase 2) to population-based recruitment involving the middle to elderly age group that should be relevant to many epidemiological studies.

Adult↗
PubMed1994

Methods for a population-based study of eye disease: the Melbourne Visual Impairment Project.

The methodology of the Melbourne Visual Impairment Project, a major population-based survey of eye disease on 3,500 randomly selected individuals aged 40 years of age and over in the Melbourne metropolitan region, is presented. The aims of the study are to determine the distribution and determinants of eye disease in an urban population; the impact of eye disease on visual function and the activities of daily living; and the accessibility of eye health care services in the community. All procedures are conducted according to a standardised protocol to allow for comparison with other population-based studies, both in Australia and overseas. Information collected from this study will be employed in the development of recommendations related to eye health care service delivery and establishment of priorities for future public education programmes and health research.

Activities of Daily Living↗
PubMed1993

Albuminuria in aborigines and Europids of south-eastern Australia.

OBJECTIVE: To determine the prevalence of albuminuria in Aborigines and Australians of European descent (Europids), as part of an epidemiological study of glucose intolerance and cardiovascular risk factors based in country towns of south-eastern Australia. DESIGN: Population-based cross-sectional study, with Aborigines and Europids of south-eastern Australia as the reference populations. METHOD: Random urine samples were collected from people aged > or = 35 years, and tested with Albuscreen (a test kit sensitive to urinary albumin concentrations of 0.03 g/L) and two other methods in the field. The samples were later analysed for the calculation of urinary albumin:creatinine ratios, which were then categorised according to cut-off points for abnormal renal function that have been proposed in the literature. RESULTS: Three hundred and six Aborigines and 553 Europids participated, with response rates of 90% and 94% respectively. According to Albuscreen, albuminuria was more common in Aborigines than in Europids. In men, 36% (95% confidence interval [CI], 20%-52%) of Aborigines exceeded the albumin concentration of 0.03 g/L, compared with 14% (CI, 9%-19%) of Europids (P < 0.01); in women, 39% (CI, 27%-51%) of Aborigines exceeded 0.03 g/L, compared with 18% (CI, 12%-24%) of Europids (P < 0.01). Sixty-one per cent (CI, 44%-78%) of Aboriginal men had a urinary albumin:creatinine ratio of > or = 1.30 mg/mmol, compared with 12% (CI, 7%-17%) of Europid men (P < 0.01); 56% (CI, 44%-68%) of Aboriginal women exceeded this cut-off point, compared with 23% (CI, 16%-30%) of Europid women (P < 0.01). CONCLUSION: A higher prevalence of renal disease in the Aboriginal population of south-eastern Australia is expected. Risk factors for renal disease in Aborigines throughout Australia require elucidation.

Adult↗
PubMed1993

Comparison of excimer laser treatment of astigmatism and myopia. The Excimer Laser and Research Group.

OBJECTIVE: To assess the safety and efficacy of excimer laser treatment of myopic astigmatism and to compare this with the excimer laser treatment of myopia. DESIGN: A prospective, open study of consecutive patients having excimer laser treatment of myopic astigmatism or myopia. SETTINGS: Patients were recruited from 18 private ophthalmic practices. PATIENTS: Fifty-four eyes received treatment for astigmatism and 66 eyes for myopia. One patient was lost to follow-up, and another underwent an ineffective ablation. INTERVENTIONS: A VISX Twenty/Twenty excimer laser was used to perform either photoastigmatic refractive keratectomy or photorefractive keratectomy. MAIN OUTCOME MEASURES: Refraction and visual acuity with and without correction were assessed preoperatively and postoperatively. RESULTS: At 6 months, 17 (85%) of the 20 patients receiving photoastigmatic refractive keratectomy were within 1 diopter of plano refraction, and 19 (95%) of 20 had uncorrected visual acuity of 6/12 (20/40) or better. For patients receiving photorefractive keratectomy, these figures were 28 (88%) of 32 patients and 28 (88%) of 32 patients, respectively. CONCLUSIONS: Excimer laser surgery offers an effective option in the treatment of myopic astigmatism.

Adult↗
PubMed1993

Hyperinsulinaemia and obesity in aborigines of south-eastern Australia, with comparisons from rural and urban Europid populations.

Diabetes is more common in Aborigines than in other Australian populations, even in groups that have lived in contact with Europids for 150 years. Prevalence data on hyperinsulinaemia and obesity from urbanized south eastern Australian Aborigines are presented with Europid comparisons. Aborigines had higher mean insulin levels than Europids. In females, mean fasting insulin was 15.5 mU/l in Aborigines, compared with 9.5 mU/l in Europids (P < 0.001). The means for males were 15.1 mU/l (Aborigines) and 8.3 (Europids) (P < 0.005). Obesity was more prevalent in Aborigines. In Aboriginal females aged 25-64 years, 41/108 (38%) had BMI > 30.0, compared with 37/208 (18%) Europids (P < 0.001). In males, the difference in the prevalence of obesity in Aborigines (17/69, 25%) and Europids (34/195, 17%) was not statistically significant. Waist-hip ratio was significantly greater among Aboriginal females (mean 0.87 in persons aged 25-64 years) than among Europids (mean 0.81, P < 0.001). In males, the mean ratio in Aborigines and Europids was the same (0.94). Abdominal obesity was most prevalent among Aboriginal females. For females aged 20-49 years, 83/110 (75%) Aborigines had a waist-hip ratio > 0.80, compared with 71/165 (43%) Europids (P < 0.001). Being overweight or obese is perceived with least accuracy by Aboriginal males of the four ethnicity/gender groups. Comparisons with national data suggest a gradient in the prevalence of obesity, lowest in urban groups, more in the country, and higher still among Aborigines, which is in reciprocal order to socio-economic status. In multivariate analyses, the association of BMI with insulin was highly significant. Hyperinsulinaemia in an Aboriginal group after many years of contact with Europids may result from environmental as well as genetic influences. Relative hyperinsulinaemia is not found among those Aborigines who have developed glucose intolerance, which could be explained by earlier pancreatic exhaustion in this group.

Adolescent↗
PubMed1993

Demographic characteristics of ophthalmic outpatients at the Royal Victorian Eye and Ear Hospital.

To investigate demographic aspects of the access to services at the Royal Victorian Eye and Ear Hospital (RVEEH), routine registration records on outpatients were linked to the population of state health regions, the distribution of ophthalmologists and projected population growth. In the six-month period September 1990 to March 1991, 19,339 persons came to the hospital (Emergency Department or Outpatients) at least once with an eye problem. Most (93%) lived in the Melbourne metropolitan area. The largest group (40%) came from Health Region 6, the Western Metropolitan region, which also has the lowest density of ophthalmologists in Victoria (1.6 per 100,000 total population, excluding ophthalmologists in the central business district of Melbourne). In the sample, 7243 patients (37%) were aged 65 years or older. Of these older patients, 75% had multiple visits to the hospital for a given illness, compared with 30% in younger patients (P < 0.01). By application of projected age-group growth rates in the Victorian population to the current profile of RVEEH outpatients, we forecast a 32% increase in the number of outpatients attending the hospital over the 15 years to 2006, 10% more than the projected population growth of 22% over this period.

Adolescent↗