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Research Review
1. Death risk lower for overweight people
New research from the US Centre for Disease Control (CDC) reported in the 7 November 2007 issue of the Journal of the American Medical Association that people who carry a few extra pounds have a lower risk of death than those who are normal weight, extremely underweight, or obese.
The study updates and expands a headline-making research of 2005, which first suggested a survival advantage for people considered overweight, but not obese.
Using additional mortality data with longer follow-up, the newer analysis examines death risk by specific cause.
Compared with people who fell into the normal-weight category, being obese was associated with an increased risk of death from cardiovascular disease, diabetes, and cancers that have been linked to obesity, such as colon, breast, esophageal, uterine, and ovarian cancers. Obesity was not associated with an increased risk of death from other cancers.
Being underweight was linked to an increased risk of death from non-cancer and non-cardiovascular causes. And being slightly overweight, but not obese, was associated with a significant decrease in the risk of death from non-cancer and non-cardiovascular causes.
Body Weight and Death
The US Centre for Disease Control (CDC) research scientist Katherine Flegal, who led the study team, says that this analysis presents a more nuanced picture of the relationship between body weight and mortality.
"I do not think this research or the previous one can be generalized to make sweeping statements. There is nothing in the new study that should change public health messages about overweight and obesity бн in both studies, being modestly overweight was associated with an overall decrease in excess mortality".
In the newly reported study, CDC researchers used data from the National Health and Nutrition Examination Survey (NHANES) to link deaths from specific causes to body weight, as measured by body mass index (BMI), which defines fatness and thinness based on height and weight.
A 5-foot-7-inch person is considered underweight with a BMI of 18.5, meaning that they weigh 118 pounds or less. Using the BMI measurement, the same person would be considered normal weight at a weight of 119 to 159 pounds, overweight at between 160 and 191 pounds, and obese at 192 pounds or more.
In the 2005 study, Flegal and colleagues speculated that carrying extra weight may not be as deadly as it once was because of better management and treatments for obesity-related diseases like diabetes and heart disease.
BMI, Age, and Mortality
But JoAnn Manson, chief of preventive medicine at Boston's Brigham and Women's Hospital, says that does not mean carrying a few extra pounds has no negative impact on health.
"We should not become more complacent about overweight and obesity because of these findings. The big picture of health extends far beyond mortality. We know that having a BMI in the overweight range is associated with many adverse health effects, including an increased risk for diabetes, hypertension, and cardiovascular disease as well as decreased physical function. And because most deaths occur among the elderly, the findings may have more relevance to people in their 70s and 80s than to younger people.
"We know that BMI is a less reliable measure of body fatness in older people, due to loss of muscle mass and weight loss due to chronic disease," says Manson.
There is also a suggestion that carrying some extra weight is associated with a survival advantage in elderly people with chronic disease. The thinking is that these people have more muscle mass and nutritional reserves that can help them fight illness and regain their strength after hospital stays.
But Manson dismisses the idea that obesity is less dangerous for older people than younger ones stating "Obesity has a major impact on mortality at all ages."
[Katherine M. Flegal is senior research scientist, Centres for Disease Control, Atlanta, USA, and JoAnn Manson is, Chief of Preventive Medicine, Brigham and Women's Hospital, Boston. Flegal, K. The Journal of the American Medical Association, April 20, 2005; Vol 293: pp 1861-1867}
References
KM Flegal, 2007. The Journal of the American Medical Association, 7 November 2007; Vol 298: pp 2028-2036.
CDC Links Extra Pounds, Lower Death Risk, Associated Press, 20 April 2005. Retrieved from New York Times, http://www.nytimes.com
2. Possible new Alzheimer's gene identified
A variant of the gene CDC2 could possibly be used as a risk marker for Alzheimer's disease. The gene variant is considerably more common among Alzheimer's patients. This is shown in a dissertation of Annica Sjolander, released by the Sahlgrenska Academy at Goteborg University in Sweden on 25 Nov 2007.
Alzheimer's disease has several different causes. Individuals may have a close relative who has developed the disease. Heredity is believed to be one of the most important factors.
"There is a previously identified Alzheimer's gene that indicates an elevated risk of developing the disease, but we want to find more genes with a strong connection to Alzheimer's. The earlier we can predict that a patient risks developing the disease, the better health care providers can prevent and treat it," says researcher Annica Sjolander.
In her dissertation, Sjolander studied different variants of a gene called CDC2. DNA analyses of blood samples from both patients and healthy individuals showed that one gene variant was considerably more common among patients with Alzheimer's disease.
"This is the first discovery of a connection between this specific gene and Alzheimer's. However, she explains that the findings must be confirmed in several other studies before one can be absolutely certain that what has been identified is a new Alzheimer's gene.
In the study this gene variant was found in roughly half of all patients with Alzheimer's, compared with 35 percent of the healthy control group. The dissertation shows that patients with Alzheimer's disease who were carriers of the gene variant also had higher levels of the protein tau, which is associated with the disease. In patients with the disease the mean level of tau in the spinal marrow fluid is about three times higher than the level in healthy individuals of the same age.
Tau proteins are microtubule-associated proteins that are abundant in neurons in the central nervous system and are less common elsewhere. These proteins interact with tubulin to stabilize microtubules and promote tubulin assembly into microtubules. Tau proteins have two ways of controlling microtubule stability: isoforms and phosphorylation. Source: http://en.wikipedia.org/wiki/Tau_protein
The gene CDC2 is responsible for one of the phases when a cell divides and is only active when cell division is in progress. Other research has shown that CDC2 in Alzheimer's patients is turned on inside nerve cells where cell division does not normally take place.
"No one knows why the gene is activated, but it may be the result of a defect in the gene. It is also possible to speculate that the body is perhaps trying to compensate for lost nerve cells by having nerve cells divide," says Sjolander.
Dissertation Title
Alzheimer's disease: The effect of tau-related genes on the pathology, neurochemistry and risk of disease.
VETENSKAPSRADET (THE SWEDISH RESEARCH COUNCIL), Regeringstgatan 56
103 78 Stockholm, http://www.vr.se
Facts reported by Alzheimer's Australia
http://www.alzheimers.org.au/content.cfm?infopageid=956#aus
Alzheimer's disease is a physical condition which attacks the brain resulting in impaired memory, thinking and behaviour . It is named after Alois Alzheimer, the German physician who, in 1907, first described it.
As brain cells shrink or disappear, abnormal material builds up as "tangles" in the centre of the brain cells, and "plaques" outside the brain cells. These disrupt messages within the brain, damaging connections between brain cells. The brain cells eventually die and this means that information cannot be recalled. As Alzheimer's disease affects each area of the brain, certain functions or abilities are lost causing dementia. Memory of recent events is the first to be affected, but as the disease progresses, long-term memory is also lost. The disease also affects many of the brain's other functions and consequently many other aspects of behaviour are affected.
Dementia is a major determining factor in precipitating entry to residential care. At least 60% of people in high care facilities and 30% of people in low care facilities have dementia. Many more have an obvious cognitive impairment (90% high care; 54% low care).
The current 2007 statistics for Australia indicates 220,000 people suffering with dementia. It is estimated that there will be 56,000 new cases of dementia by the end of 2007. The number is expected to be 731,000 by 2050 -- an increase of 327% while the total population increases by less than 40%.
Researchers are rapidly learning more about the chemical changes that damage brain cells in Alzheimer's disease, but apart from the few individuals with Familial Alzheimer's disease (caused by genetic mutation identified only in a small number of people in Australia), it is not known why one individual gets Alzheimer's disease and another does not.
A variety of other suspected causes are being investigated, including factors in the environment, biochemical disturbances and immune processes. The cause may vary from person to person and may be due to one factor or a number of factors.
3. Drugs may not delay onset of dementia
A new research, released on 26 November 2007, suggests that drugs may not delay onset of dementia. In this connection, researchers have examined the evidence in favour of giving people considered to be close to developing dementia the drugs that are most commonly used to treat the condition itself. They have concluded that these drugs (cholinesterase inhibitors) do not seem to delay the appearance of Alzheimer's disease or other forms of dementia.
Three cholinesterase inhibitors - donepezil, rivastigmine and galantamine - are currently approved for use in mild-to-moderate Alzheimer's disease. Some experts are not convinced that they are effective, but other experts and patient support groups have called for the drugs to be given to people with "mild cognitive impairment (MCI)" - the term that is used to describe the condition where people have memory problems that are more severe than those normally seen in others of their age, but otherwise have no symptoms of dementia. It is believed that people with MCI are at high risk of developing Alzheimer's disease.
Dr Raschetti and colleagues at Italy's National Centre for Epidemiology, Surveillance and Health Promotion in Rome conducted a systematic review of the data from clinical trials that had addressed the use of cholinesterase inhibitors with MCI patients.
In none of the six trials that they examined did the use of the drugs significantly reduce the rate of progression from MCI to dementia. One problem that came to light during their review was that there is no generally accepted precise definition for MCI. There was therefore some variation between the trials in the mental state of the people given the drugs.
Thus, Raschetti and his team have called for more clinical trials to be done, but using a single agreed definition of mild cognitive impairment. Until such trials have found a benefit from using cholinesterase inhibitors in this way, there seems to be no justification for doctors to do so in clinical practice.
Citation
Raschetti R, Albanese E, Vanacore N, Maggini M, 2007. Cholinesterase inhibitors in mild cognitive impairment: A systematic review of randomised trials. PLoS Med 4(11): e338, http://medicine.plosjournals.org
4. Brain imaging reveals gender differences in how individuals cope under stress
According to a study that appeared in the 20 November 2007 issue of SCAN (Social Cognitive and Affective Neuroscience), researchers of the University Pennsylvania School of Medicine discuss how men and women differ in their neural responses to psychological stress.
"We found that different parts of the brain activate with different spatial and temporal profiles for men and women when they are faced with performance-related stress," says J.J. Wang, Assistant Professor of Radiology and Neurology, and lead author of the study.
These findings suggest that stress responses may be fundamentally different in each gender, sometimes characterized as "fight-or-flight" in men and "tend-and-befriend" in women. Evolutionarily, males may have had to confront a stressor either by overcoming or fleeing it, while women may have instead responded by nurturing offspring and affiliating with social groups that maximize the survival of the species in times of adversity.
The "fight-or-flight" response is associated with the main stress hormone system that produces cortisol in the human body -- the hypothalamic-pituitary-adrenal (HPA) axis.
Thirty-two healthy subjects -- 16 females and 16 males -- received fMRI (functional Magnetic Resonance Imaging) scans before, during and after they underwent a challenging arithmetic task (serial subtraction of 13 from a 4 digit number), under pressure. To increase the level of stress, the researchers frequently prompted participants for a faster performance and asked them to restart the task if they responded incorrectly. As a low stress control condition, participants were asked to count backward without pressure.
The researchers measured heart rate, cortisol levels (a stress hormone), subjects' perceived stress levels throughout the experiments, and regional cerebral blood flow (CBF), which provides a marker of regional brain function. In men, it was found that stress was associated with increased CBF in the right prefrontal cortex and CBF reduction in the left orbit frontal cortex. In women, the limbic system -- a part of the brain primarily involved in emotion -- was activated when they were under stress. Both men and women's brain activation lasted beyond the stress task, but the lasting response in the female brain was stronger. The neural response among the men was associated with higher levels of cortisol, whereas women did not have as much association between brain activation to stress and cortisol changes.
"Women have twice the rate of depression and anxiety disorders compared to men," notes Dr. Wang.
"Knowing that women respond to stress by increasing activity in brain regions involved with emotion, and that these changes last longer than in men, may help us begin to explain the gender differences in the incidence of mood disorders."
Additional researchers involved with this study are Marc Korczykowski, Penn; Hengyi Rao, Penn; Yong Fan, Penn; John Pluta, Penn; Ruben Gur, Penn; Bruce McEwen, The Rockefeller University; and John Detre, Penn. The study was conducted at the Centre for Functional Neuro-imaging at the University of Pennsylvania.
References
Medical News Today, http://www.medicalnewstoday.com
Kate Olderman Tavella, University of Pennsylvania School of Medicine
NEWS
1. Australia's mothers and babies 2005
A new report released on 28 November 2007 by the Australian Institute of Health and Welfare (AIHW) provides information on births in Australia from perinatal data collections for each state and territory.
This is a fifteenth report of AIHW. This edition includes a chapter on socioeconomic status of mothers. The report is produced by the AIHW National Perinatal Statistics Unit based at the University of New South Wales and can be used by researchers, academics, students, policy makers and health service planners, and those providing services in reproductive health, www.aihw.gov.au
AIHW cat. No. PER 40 Available from CanPrint for $30.00 (1300 889 873)
2. Alcohol killing our kids - Australian Medical Association (AMA)
As Schoolies Week and alcohol combine to produce tragic headlines about death and injury to young people and reports of antisocial behaviour by drunken teenagers, the AMA is calling for stronger policies to curb dangerous excess alcohol consumption.
According to AMA President, Rosanna Capolingua, irresponsible alcohol consumption causes harm across all age groups in the community, but the senseless loss of young lives through alcohol abuse must be stopped as a priority.
"Alcohol abuse by young people, highlighted by the culture of binge drinking, is harming the health of thousands of Australians every year. Alcohol is second only to tobacco as a preventable cause of drug-related death and hospitalisations in Australia", says Capolingua.
The National Health and Medical Research Council (NHMRC) reports that alcohol abuse costs Australia $15.3 billion a year through alcohol-related crime and violence, treatment costs, loss of productivity, and premature death. According to NHMRC data, alcohol accounts for 13 per cent of all deaths among 14-17 year olds. Further, estimates indicate that one Australian teenager dies and more than 60 are hospitalised each week from alcohol-related causes.
"The binge drinking culture is alive and well in Australia and urgent action is needed to re-educate Australians about safe levels of alcohol consumption. The most frightening thing is that binge drinking has hit epidemic proportions among our young people. There is a disturbing acceptance, or even celebration, of excess drinking in Australia. Many people view it as a national pastime to be proud of.
"Young people are placing increasing social importance on how drunk they are when they go out, and young women in particular make a point of 'keeping up' with their male friends'. We have to seriously question a society where young adults start their evening by getting drunk at home so they can enjoy their night out more. The drunken public behaviour of role models and celebrities, such as sporting heroes, is just helping to glamorise binge drinking in the eyes of Australians.
"People simply are not aware of the tragic consequences of binge drinking. Many people just think about their hangover the next morning, and do not consider the long-term effects like brain damage or heart disease, let alone the immediate danger they may put themselves in while they are intoxicated."
A study by Alcohol Related Brain Injury Australian Services indicates that two million Australians, or one in eight adults, are at risk of permanent brain damage from alcohol.
At the same time, patterns of alcohol consumption have changed to reflect new products, with a doubling since 2001 in the proportion of teenagers consuming pre-mixed spirits.
In this connection, Capolingua adds that while initiatives such as the new NHMRC alcohol guidelines were helping to raise awareness of safe drinking, many public education campaigns were not effective in encouraging people to moderate their drinking.
"Alcohol education campaigns often focus on the number of standard drinks and this does not always make sense to people. People often think of the amount of alcohol they have consumed in terms of how many glasses they have had, how long they have been drinking, or how drunk they feel. It can be difficult in a social situation to judge what a standard drink is.
"This inconsistency in the way we refer to safe drinking levels makes it difficult to raise public awareness about alcohol-related harm. The harmful effects of alcohol abuse, including binge drinking, impact not just on the drinker, but on friends and family, the workplace, the wider community, and the health system.
"We need national public awareness campaigns that clearly and simply show the dangers of alcohol abuse, and which use language that people can easily understand."
The AMA is committed to achieving a reduction in the incidence of hazardous and harmful levels of alcohol consumption and is calling for:
- A partnership between government, industry, and community representatives to mobilise public opinion to recognise that hazardous alcohol consumption is socially unacceptable;
- increased taxes that directly reflect the total volume of alcohol in products to encourage a shift to consumption of products containing less alcohol;
- standard alcohol drink labelling that includes information on the health and social risk associated with excess consumption and which is displayed in a prominent position on all alcohol containers and is easily understood by the consumer;
- all advertisements for alcoholic beverages to encourage no more than the NHMRC-recommended levels of alcohol consumption, and to raise awareness about hazardous levels of consumption;
- stricter controls to curb the marketing of products like 'alcopops' (sweetened ready-to-drink alcoholic beverages) to teenagers; and
- effective, wide-reaching public education campaigns highlighting the risks associated with binge drinking, and based on appropriate consultation and engagement with the key target audience groups.
References
Medical News Today, http://www.medicalnewstoday.com/articles/89323.php
Australian Medical Association (AMA), http://www.ama.com.au
Monika Bhatia
Editor, Health and Ageing
11 December 2007