Saturday, February 14, 2009

Another flawed attack on passive smoking

Before I comment on this, let me say that I loathe and detest tobacco smoke and consider those who light up in the presence of non-smokers to be pathetic and offensive addicts. So it would suit me if I could endorse the conclusions of the article below. But I cannot. It is one of a long line of attempts to portray secondhand smoke as harmful but the best research on the topic indicates that it is not . Existing research, however, has mainly looked at passive smoking as a cause of heart and lung disease. The study below takes a new tack. It tries to show that passive smoking makes you stupid.

The research below appears to have been done with unusual care but is still incapable of supporting its conclusions. It found that those who associated with smokers a lot had lower mental alertness. They were slower to process instructions that they were given. But we have known for years that smoking correlates with all indices of social disadvantage, including low IQ. I am delighted to note however that the researchers took extensive account of that and controlled for a whole range of social class indicators. That is rare sophistication in epidemiological research. They did NOT however control for IQ -- which was arguably the most important thing to control for in the circumstances. IQ correlates strongly with mental speed.

So what was in fact found was that low IQ people tend to flock together. It was shown that people who associate with dummies (i.e. smokers) a lot also tend to be dummies (as measured by the tests used in the study below). The study tells us nothing about passive smoking.

Exposure to second-hand smoke boosts the risk of dementia and other cognitive problems, even among people who have never smoked, the largest study of its kind said. Ill effects on non-smokers of constant exposure to tobacco smoke include an increased risk of lung cancer, diabetes, cardiovascular disease, stroke and death, earlier research has shown. As for the impact on brain function, active smoking has been found to impair the mind but the evidence for passive smoking has until now been sketchy.

Using new methods in the largest clinical trial to date, a team led by Cambridge University professor David Llewellyn found that even people who had never smoked but kept constant company with smokers performed less well in cognitive tests. The investigation focused on nearly 5000 adults over the age of 50 who were former smokers or who had never smoked.

The volunteers were divided into four groups according to their exposure to passive smoking. This was determined by saliva samples, which were tested for a by-product of nicotine called cotinine. Cotinine lingers in the saliva for about 25 days. The higher the levels of cotinine, the higher the exposure to recent second-hand smoke.

The volunteers then took neuro-psychological tests that assessed brain function and cognitive abilities, focusing on memory and the ability to work with numbers and words. Using the lowest cotinine group as a benchmark, the researchers found a clear and progressively stronger link between impairment in brain function and exposure to second-hand smoke. In the most-exposed group, the risk of cognitive impairment was 44 per cent higher than the benchmark group.

Factors such as age and medical condition, including a history of heart disease, that could have skewed the outcome were all taken into account. "A similar pattern of associations was observed for never smokers and former smokers," said the study, published in the British Medical Journal (BMJ). "Given the ongoing international policy debate on exposure to second-hand smoke, this is a topic of major public health significance."

Governments in North America, Australia and Europe have progressively enacted "smoke-free" legislation for the workplaces, bars, restaurants and other public places over the last 15 years.

SOURCE. The original academic journal article is: Llewellyn, D.J. et al. (2009) "Exposure to secondhand smoke and cognitive impairment in non-smokers: national cross sectional study with cotinine measurement" BMJ 338:b462

Sleep could help prevent the common cold

That bed rest is the ONLY cure for most viral infections has long been accepted but it is good to see some confirmation of that

FLUFF up the pillows and pull up the covers. Preventing the common cold may be as easy as getting more sleep, a study in the United States has revealed. Researchers paid healthy adults $US800 to have cold viruses sprayed up their noses, then wait five days in a hotel to see if they became sick. Habitual eight-hour sleepers were much less likely to get sick than those who slept less than seven hours or slept fitfully. "The longer you sleep, the better off you are, the less susceptible you are to colds," said lead author Sheldon Cohen, who studies the effects of stress on health at Pittsburgh's Carnegie Mellon University. Prior research has suggested that sleep boosts the immune system at the cell level.

This is the first study to show small sleep disturbances increasing the risk of getting sick, said Michael Irwin, a doctor who researches immune response at the University of California, Los Angeles, and was not involved in the study. "The message is to maintain regular sleep habits because those are really critical for health," Irwin said. During cold season, staying out of range of sneezing relatives and co-workers may be impossible.

The study, which appeared in the Archives of Internal Medicine, mimicked those conditions by exposing participants to a common cold virus - rhinovirus - and most became infected with it. But not everyone suffered cold symptoms. The people who slept less than seven hours a night in the weeks before they were exposed to the virus were three times more likely to catch a cold than those who slept eight hours or more.

To find willing cold victims, researchers placed ads and recruited 78 men and 75 women, all healthy and willing to go one-on-one against the virus. They ranged in age from 21 to 55. First, their sleep habits were recorded for two weeks. Every evening, researchers interviewed them by phone about their sleep the night before. Subjects were asked what time they went to bed, what time they got up, how much time they spent awake during the night and if they felt rested in the morning.

Then they checked into a hotel where the virus was squirted up their noses. After five days, the virus had done its work, infecting 135 of the 153 volunteers. But only 54 people became sick. Researchers measured their runny noses by weighing their used tissues. They tested for congestion by squirting dye in the subjects' noses to see how long it took to get to the back of their throats.

Sleeping fitfully also was tied to greater risk of catching a cold. Those who tossed and turned more than 8 per cent of their time in bed were five times more likely to get sick than those who were sleepless only 2 per cent of the time. Surprisingly, feeling rested was not linked to staying well. Cohen said he's not sure why that is, other than feeling rested is more subjective than recalling bedtime and wake-up time.

The researchers took into account other factors that make people more susceptible such as stress, smoking and drinking, and lack of exercise, and they still saw a connection between sleep and resisting a cold.

Cold symptoms such as congestion and sore throat are caused by the body's fight against a virus, rather than the virus itself, Cohen said. People whose bodies make the perfect amount of infection-fighting proteins called cytokines will not even know they are fighting a virus. But if their bodies make too many, they feel sick. Sleep may fine-tune the body's immune response, Cohen said, helping regulate the perfect response.

Prior research has tied lack of sleep to greater risk of weight gain, heart disease, high blood pressure, stroke and diabetes.

Daniel Buysse, a doctor doing sleep researcher at the University of Pittsburgh, said spending too much time in bed can lead to more interrupted sleep, which in this study "seems to be even worse than short sleep" for increasing the risk of catching a cold. If it takes a long time to fall asleep or if you are restless during the night, "you would probably benefit from spending a little less time in bed", Buysse said. "If you fall asleep instantly, have no wakefulness during the night, and are sleepy during the day, you would probably benefit from spending a little more time in bed." Buysse was not directly involved in the research, although he commented on an early draft of the study. The study was funded by grants from the National Institutes of Health and the MacArthur Foundation.

Harvard sleep researcher Sat Bir Khalsa said people do not need to turn to prescription sleep aids to improve their sleep. Setting a regular bedtime, moving computers and televisions out of the bedroom and, when restless, getting out of bed for a while and doing something soothing can help. His research focuses on treating insomnia with yoga.

As preventive measures, vitamin C and herbal supplements have not lived up to their reputation in rigorous studies. Cohen said research has shown people who get more exercise, drink moderately and have lower stress also get fewer colds.


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