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Biomedical subjects

Anthony J McMichael

Publications and source records attributed to Anthony J McMichael.

At least 19 recordsLinked to original sources
PubMed2006

Is the current public health message on UV exposure correct?

Current sun safety messages stress the importance of sun protection in avoiding the consequences of excessive exposure to ultraviolet radiation (UVR), such as skin cancers, cataracts and other eye diseases, and viral infections caused by UV-induced immunosuppression. However, adequate exposure to UVR has an important role in human health, primarily through UV-induced production of vitamin D, a hormone essential to bone health. Vitamin D insufficiency may be associated with increased risks of some cancers, autoimmune diseases and mental health disorders such as schizophrenia. Here, we review the evolution of current sun exposure practices and sun-safe messages and consider not only the benefits, but also the detrimental effects that such messages may have. UVR-induced vitamin D production can be inhibited by factors such as deep skin pigmentation, indoor lifestyles, older age, sun avoidance behaviours and clothing habits that limit skin exposure, with deleterious consequences for health. There is some early evidence that sun-safe messages are beginning to cause a decrease in skin cancer rates in young people. After the widespread promotion of sun safety, it may now be appropriate to refine public health messages to take better account of variations between groups and their susceptibility to the dangers and benefits of sun exposure.

Communication↗
PubMed2006

Estimates of beneficial and harmful sun exposure times during the year for major Australian population centres.

OBJECTIVE: To examine the influence of geographical and seasonal factors on duration of solar ultraviolet (UV) radiation exposure of skin to produce recommended vitamin D levels without producing erythema. DESIGN AND SETTING: An ecological study using daily Ultraviolet Index (UVI) data collected in major population centres across Australia for 1 year (1 January - 31 December 2001) to calculate sun exposure times for recommended vitamin D production and erythema. MAIN OUTCOME MEASURES: Sun exposure times to produce either serum vitamin D concentrations equivalent to an oral intake of 200-600 IU/day or erythema for people aged 19-50 years with fair skin (Fitzpatrick type II skin) exposing 15% of the body. RESULTS: In January, across Australia, 2-14 minutes of sun three to four times per week at 12:00 is sufficient to ensure recommended vitamin D production in fair-skinned people with 15% of the body exposed. However, erythema can occur in as little as 8 minutes. By contrast, at 10:00 and 15:00, there is a greater difference between exposure time to produce erythema and that to produce recommended vitamin D levels, thereby reducing the risk of sunburn from overexposure. From October to March, around 10-15 minutes of sun exposure at around 10:00 or 15:00 three to four times per week should be enough for fair-skinned people across Australia to produce recommended vitamin D levels. Longer exposure times are needed from April to September, particularly in southern regions of Australia. CONCLUSION: Our study reinforces the importance of existing sun protection messages for the summer months throughout Australia. However, fair-skinned people should be able to obtain sufficient vitamin D from short periods of unprotected sun exposure of the face, arms and hands outside of the peak UV period (10:00-15:00) throughout Australia for most of the year. The greater variability in sun exposure times during winter, means that optimal sun exposure advice should be tailored to each location.

Adult↗
PubMed2006

Climate change and human health: present and future risks.

There is near unanimous scientific consensus that greenhouse gas emissions generated by human activity will change Earth's climate. The recent (globally averaged) warming by 0.5 degrees C is partly attributable to such anthropogenic emissions. Climate change will affect human health in many ways-mostly adversely. Here, we summarise the epidemiological evidence of how climate variations and trends affect various health outcomes. We assess the little evidence there is that recent global warming has already affected some health outcomes. We review the published estimates of future health effects of climate change over coming decades. Research so far has mostly focused on thermal stress, extreme weather events, and infectious diseases, with some attention to estimates of future regional food yields and hunger prevalence. An emerging broader approach addresses a wider spectrum of health risks due to the social, demographic, and economic disruptions of climate change. Evidence and anticipation of adverse health effects will strengthen the case for pre-emptive policies, and will also guide priorities for planned adaptive strategies.

Aged↗
PubMed2006

Phyto-oestrogen intake and plasma concentrations in South Asian and native British women resident in England.

Phyto-oestrogens, naturally occurring hormone-like chemicals in plant food, may play a protective role against hormone-related chronic diseases. South Asian migrants in the UK have a lower incidence of hormone-related cancer than their hosts but the extent to which this difference may be due to phytoestrogen intake is not known. The aim was to compare habitual phytoestrogen intake in first-generation South Asian migrant women and native British women. South Asian (n 221) and native British women (n 50) were recruited from general practitioner lists and were asked to provide monthly 24 h recalls for a period of 1 year. An enhanced phytoestrogen database was compiled using data from a literature search and unpublished data. A sub-sample of South Asian women (n 100) and the native British women (n 40) also provided blood samples every 3 months during the 1-year period. The median daily intakes (microg/d) of isoflavones (184.2 v. 333.9) and lignans (110.8 v. 148.8) were significantly lower in South Asians than in the native British (P<0.001, P=0.04 respectively). There were no significant differences in mean plasma isoflavone levels (nmol/l) but plasma enterolactone was significantly lower in the South Asians (13.9 (SD 17.5) v. 28.5 (SD 23.3), P<0.001). The main sources of phytoestrogens were bread and vegetables in both ethnic groups. Habitual phytoestrogen intake in South Asian and native British women was below 1 mg/d and was higher in the native British diet. The present study does not support the hypothesis that differences in phytoestrogen intake, or in circulating levels, could explain differences in hormone-related cancer risks between these two populations.

Adult↗
PubMed2006

Weather variability, tides, and Barmah Forest virus disease in the Gladstone region, Australia.

In this study we examined the impact of weather variability and tides on the transmission of Barmah Forest virus (BFV) disease and developed a weather-based forecasting model for BFV disease in the Gladstone region, Australia. We used seasonal autoregressive integrated moving-average (SARIMA) models to determine the contribution of weather variables to BFV transmission after the time-series data of response and explanatory variables were made stationary through seasonal differencing. We obtained data on the monthly counts of BFV cases, weather variables (e.g., mean minimum and maximum temperature, total rainfall, and mean relative humidity), high and low tides, and the population size in the Gladstone region between January 1992 and December 2001 from the Queensland Department of Health, Australian Bureau of Meteorology, Queensland Department of Transport, and Australian Bureau of Statistics, respectively. The SARIMA model shows that the 5-month moving average of minimum temperature (b=0.15, p-value<0.001) was statistically significantly and positively associated with BFV disease, whereas high tide in the current month (b=-1.03, p-value=0.04) was statistically significantly and inversely associated with it. However, no significant association was found for other variables. These results may be applied to forecast the occurrence of BFV disease and to use public health resources in BFV control and prevention.

Alphavirus↗
PubMed2005

Nonstationary influence of El Niño on the synchronous dengue epidemics in Thailand.

BACKGROUND: Several factors, including environmental and climatic factors, influence the transmission of vector-borne diseases. Nevertheless, the identification and relative importance of climatic factors for vector-borne diseases remain controversial. Dengue is the world's most important viral vector-borne disease, and the controversy about climatic effects also applies in this case. Here we address the role of climate variability in shaping the interannual pattern of dengue epidemics. METHODS AND FINDINGS: We have analysed monthly data for Thailand from 1983 to 1997 using wavelet approaches that can describe nonstationary phenomena and that also allow the quantification of nonstationary associations between time series. We report a strong association between monthly dengue incidence in Thailand and the dynamics of El Niño for the 2-3-y periodic mode. This association is nonstationary, seen only from 1986 to 1992, and appears to have a major influence on the synchrony of dengue epidemics in Thailand. CONCLUSION: The underlying mechanism for the synchronisation of dengue epidemics may resemble that of a pacemaker, in which intrinsic disease dynamics interact with climate variations driven by El Niño to propagate travelling waves of infection. When association with El Niño is strong in the 2-3-y periodic mode, one observes high synchrony of dengue epidemics over Thailand. When this association is absent, the seasonal dynamics become dominant and the synchrony initiated in Bangkok collapses.

Climate↗
PubMed2005

Integrating nutrition with ecology: balancing the health of humans and biosphere.

OBJECTIVE: To show that current rates of global population growth, production and consumption of food, and use of living and physical resources, are evidently not sustainable. To consider ways in which nutrition and allied sciences can respond to this great challenge of the twenty-first century. METHOD: Past, current and future projected trends in production and consumption patterns are examined. These show that overall present and projected patterns cannot be sustained; and also show increasing unacceptable inequity between and within rich and poor regions and countries. DISCUSSION: Nutrition science classically focuses on nutrients in relation to human physiology, metabolism, growth, health and disease. The social and environmental conditions of the modern, interconnected, market-oriented world, and the consequences for food production and consumption, are extending the research and policy agenda with which nutrition science must now urgently engage. Historically, much attention has been paid to eliminating nutritional deficiency states, and this remains an important task. In modern urban populations 'malnutrition' encompasses new forms of dietary imbalance, especially excesses of certain nutrients. These contribute to various non-communicable diseases and, particularly, to overweight/obesity and its attendant metabolic derangements and disease risks. As a mass phenomenon the current surge in obesity has no historical precedent. The escalating impact of humankind on the natural environment, with its ramifications for present and future food production, is also unprecedented. CONCLUSION: The essential challenge for nutrition science is to develop new understanding and strategies to enable a balance between promoting, equitably, the health of humans while sustaining the long-term health of the biosphere. Extension of nutrition science and food policy to meet those goals will be aided by understanding better how dietary conditions shaped the biological evolution of humankind. The fundamental long-term task is to integrate human health with the health of the biosphere.

Diet↗
PubMed2005

The principles, definition and dimensions of the new nutrition science.

OBJECTIVE: To specify the principles, definition and dimensions of the new nutrition science. PURPOSE: To identify nutrition, with its application in food and nutrition policy, as a science with great width and breadth of vision and scope, in order that it can fully contribute to the preservation, maintenance, development and sustenance of life on Earth. METHOD: A brief overview shows that current conventional nutrition is defined as a biological science, although its governing and guiding principles are implicit only, and no generally agreed definition is evident. Following are agreements on the principles, definition and dimensions of the new nutrition science, made by the authors as participants at a workshop on this theme held on 5-8 April 2005 at the Schloss Rauischholzhausen, Justus-Liebig University, Giessen, Germany. RESULT: Nutrition science as here specified will retain its current 'classical' identity as a biological science, within a broader and integrated conceptual framework, and will also be confirmed as a social and environmental science. As such it will be concerned with personal and population health, and with planetary health--the welfare and future of the whole physical and living world of which humans are a part.

Biological Science Disciplines↗
PubMed2004

Vulnerability to winter mortality in elderly people in Britain: population based study.

OBJECTIVE: To examine the determinants of vulnerability to winter mortality in elderly British people. DESIGN: Population based cohort study (119,389 person years of follow up). SETTING: 106 general practices from the Medical Research Council trial of assessment and management of older people in Britain. PARTICIPANTS: People aged > or = 75 years. MAIN OUTCOME MEASURES: Mortality (10,123 deaths) determined by follow up through the Office for National Statistics. RESULTS: Month to month variation accounted for 17% of annual all cause mortality, but only 7.8% after adjustment for temperature. The overall winter:non-winter rate ratio was 1.31 (95% confidence interval 1.26 to 1.36). There was little evidence that this ratio varied by geographical region, age, or any of the personal, socioeconomic, or clinical factors examined, with two exceptions: after adjustment for all major covariates the winter:non-winter ratio in women compared with men was 1.11 (1.00 to 1.23), and those with a self reported history of respiratory illness had a winter:non-winter ratio of 1.20 (1.08 to 1.34) times that of people without a history of respiratory illness. There was no evidence that socioeconomic deprivation or self reported financial worries were predictive of winter death. CONCLUSION: Except for female sex and pre-existing respiratory illness, there was little evidence for vulnerability to winter death associated with factors thought to lead to vulnerability. The lack of socioeconomic gradient suggests that policies aimed at relief of fuel poverty may need to be supplemented by additional measures to tackle the burden of excess winter deaths in elderly people.

Aged↗
PubMed2004

Mortality trends and setbacks: global convergence or divergence?

Health trends over much of the past century have been generally, and notably, positive throughout the world. In several regions, however, life expectancy has declined over the past 1-2 decades. This trend suggests that the expectation that emerged in the 1960s and 1970s of worldwide gains and convergence in population health status is not guaranteed by a general deterministic process. National populations can now be clearly grouped into those that have achieved rapid gains in life expectancy; those whose gains are slower or are perhaps plateauing; and those in which the trends have reversed. Over the past two centuries, outside times of war and famine, such reversals have been rare. Exploration of these varied population health trends elucidates better the close relation between population health and the processes of economic, social, and technological change. Such analysis has shown that the health status of human populations should be a guiding criterion in the debate on sustainable development.

Age Factors↗
PubMed2004

Phyto-oestrogen intake and breast cancer risk in South Asian women in England: findings from a population-based case-control study.

OBJECTIVE: This study investigates whether intake of phyto-oestrogens is associated with breast cancer risk in South Asian women from the Indian subcontinent, whose diet is rich in pulses and vegetables but poor in soyfoods. METHODS: A total of 240 South Asian breast cancer cases living in England and 477 age-matched population-based controls were recruited into the study. Dietary intake was measured using a validated food frequency questionnaire. Conditional logistic regression models were used to estimate the effect of phyto-oestrogen intake on breast cancer risk. RESULTS: After adjustment for known breast cancer risk factors and total energy intake, there was moderate evidence of a dose-effect response in the odds of breast cancer with isoflavone intake (p-value for trend 0.08), with women in the top quartile having approximately half the odds of breast cancer of those in the bottom one (odds ratio (OR) 0.58, 95% confidence interval (CI) 0.33, 1.00) but with no reductions in the odds for women in the second and third quartiles. The ORs for second, third and highest quartiles of total lignan intake compared to the lowest were 0.78 (95% CI 0.48, 1.26), 0.74 (0.46, 1.19) and 0.66 (0.41, 1.07), respectively, again with moderate evidence of a linear dose-effect response (p-value for trend 0.09). Further adjustment for non-startch polysaccharides (NSP) intake slightly weakened the phyto-oestrogens-breast cancer associations. CONCLUSIONS: These findings are consistent with the possibility that high phyto-oestrogen intake may protect against breast cancer, but further research is required to confirm this hypothesis.

Adult↗
PubMed2004

Social and environmental risk factors in the emergence of infectious diseases.

Fifty years ago, the age-old scourge of infectious disease was receding in the developed world in response to improved public health measures, while the advent of antibiotics, better vaccines, insecticides and improved surveillance held the promise of eradicating residual problems. By the late twentieth century, however, an increase in the emergence and re-emergence of infectious diseases was evident in many parts of the world. This upturn looms as the fourth major transition in human-microbe relationships since the advent of agriculture around 10,000 years ago. About 30 new diseases have been identified, including Legionnaires' disease, human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), hepatitis C, bovine spongiform encephalopathy (BSE)/variant Creutzfeldt-Jakob disease (vCJD), Nipah virus, several viral hemorrhagic fevers and, most recently, severe acute respiratory syndrome (SARS) and avian influenza. The emergence of these diseases, and resurgence of old ones like tuberculosis and cholera, reflects various changes in human ecology: rural-to-urban migration resulting in high-density peri-urban slums; increasing long-distance mobility and trade; the social disruption of war and conflict; changes in personal behavior; and, increasingly, human-induced global changes, including widespread forest clearance and climate change. Political ignorance, denial and obduracy (as with HIV/AIDS) further compound the risks. The use and misuse of medical technology also pose risks, such as drug-resistant microbes and contaminated equipment or biological medicines. A better understanding of the evolving social dynamics of emerging infectious diseases ought to help us to anticipate and hopefully ameliorate current and future risks.

Cardiovascular Diseases↗