Thursday, June 10, 2010

Passive smoking 'increases the risk of mental health problems'

Since some very strong studies have shown no adverse health effects of passive smoking, the study below must be approached with caution. And the alarm bells really ring when we find that the effects were confined to men. Are male and female brains all that different?

The study is of course epidemiological rather than experimental so there is a lot of room for "holes" in its conclusions. There are three important holes in the study: Taxonomy, direction of causation assumptions and social class measurement.

Taxonomy: The researchers wisely reclassified people who claimed to be non-smokers if they had high levels of nicotine metabolites in their blood and used primarily levels of such metabolites (cotinine) as their classificatory variable. But that does cast something of a pall over their study. All that they really have is the association between mental health and cotinine level. How much of the cotinine level is actually due to passive smoke versus light smoking we do not know. If just some "non-smokers" were in fact light smokers, the whole study falls into a pit. All observed effects could be due simply to the light smokers in the sample.

Causation: The researchers observed a clear gradient between levels of cotinine and mental health. Regular smokers were the maddest. But that exposes the direction of causation assumptions. Mentally ill people regularly use nicotine as a form of self-medication: Almost all mad people smoke. So again we ask whether some of the mentally ill "non-smokers" were in fact light smokers and add the consideration that they may smoke BECAUSE they were mentally ill rather than the other way around.

Social class: An occupational categorization only was used. Education, IQ and income were not considered, even though all have social class implications and are not well correlated with one another. And since dumber people, less educated and poorer people are all more likely to smoke -- and presumably associate with similar people who do -- that was an omission large enough to leave the results moot all by itself. We may simply be seeing social class effects on mental health

The journal article is "Objectively Assessed Secondhand Smoke Exposure and Mental Health in Adults"

Passive smoking is known to increase a person's risk of heart disease and lung cancer, now research suggests it could affect mental health as well.

Scientists from the University College of London found that non-smokers exposed to a lot of secondhand smoke were 50 per cent more likely to suffer from psychological distress than those not exposed to other people's smoke.

Their risk of being admitted to a psychiatric hospital over the next six years was nearly tripled, while it was almost quadrupled for smokers.
The study found the higher a person's secondhand smoke exposure, the greater their risk of psychological distress

The study found the higher a person's secondhand smoke exposure, the greater their risk of psychological distress

Passive smoking is very common with one US study finding evidence of secondhand smoke in 60 per cent of non-smokers.

Dr Mark Hamer of UCL said that although the physical effects have been measured there is 'very limited information' on how other people's smoke might affect mental health.

To investigate, Dr Hamer and his colleagues studied 5,560 non-smoking adults and 2,595 smoking adults, none of whom had a history of mental illness.

The study subjects answered questions about psychological distress and admissions to psychiatric hospitals were tracked for six years.

Exposure to secondhand smoke among non-smokers was determined using saliva levels of cotinine, which is formed when nicotine is broken down in the body and is an established marker of nicotine exposure.

A total of 14.5 percent of study subjects reported psychological distress.

According to the investigators, the higher a person's secondhand smoke exposure, the greater their risk of psychological distress, while the risk was highest for people who were themselves smokers.

People with high exposure to secondhand smoke (those with the highest cotinine levels) who didn't actually smoke themselves were 62 per cent more likely to report psychological distress than those unexposed to secondhand smoke, while the risk for smokers was 2.45 times greater.

During follow-up, which averaged about six years, 41 people were admitted to psychiatric hospitals. The risk of hospitalization was 2.8 times greater for secondhand smokers compared to people not exposed to secondhand smoke, while it was 3.7 times greater for smokers.

The effects were stronger for never-smokers than for ex-smokers, Dr Hamer noted; the fact that former smokers were able to quit could suggest they were intrinsically less vulnerable to the effects of nicotine.

Dr Hamer said the link remained even after he and his colleagues accounted for social status, alcohol intake and other factors that could influence both the risk of mental health problems and the likelihood of being exposed to secondhand smoke. 'We did see pretty robust associations that remained after those adjustments,' he said.

Moreover, Dr Hamer and colleagues note that animal studies have hinted that tobacco may depress a person's mood and some human studies have also suggested a potential link between smoking and depression.

'Taken together, therefore, our data are consistent with other emerging evidence to suggest a causal role of nicotine exposure in mental health,' the investigators concluded in their study that appeared in the Archives of General Psychiatry.


Bad health news for shorties

One wise comment below: "We need to understand the mechanism behind it". The causal chain is certainly not clear but it is consistent with other findings suggesting a general syndrome of biological fitness. Nutrition seems an unlikely explanation in a place as well-fed as Europe

Short people have a 50 percent higher risk of having a heart problem or dying from one than tall people, a new study says, though weight, blood pressure and smoking habits remain more important factors.

Previous studies have suggested a link between height and heart problems like angina, heart attacks and angioplasties. This is the first major review of such studies, including research from around the world, confirming the relationship.

Researchers in Finland looked at 52 previous papers with data on height and heart problems in more than 3 million men and women.

Experts did not consider patients' heights objectively, but within the context of a particular country's population. They found the shortest people in the population were one and a half times more likely to have heart problems or die from them than the tallest people.

On average, short people were under 161 centimetres and tall people were at least 174 centimetres.

The study was paid for by the Finnish Foundation for Cardiovascular Research and others. It was published online Wednesday in the European Heart Journal.

"We don't want to scare short people, but perhaps they should be extra cautious about their lifestyle," said Borge Nordestgaard, a professor of genetic epidemiology at the University of Copenhagen. He was not connected to the study.

Height's impact on heart disease was still less important than things like smoking, which increases the chance of a heart ailment by up to four times, he said.

Scientists aren't sure why short people might be more susceptible to heart problems, but think there could be several explanations. Being short might be a result of being poor, meaning people of small stature could be undernourished and vulnerable to health problems in general.

Experts also suggested there could be a biological explanation, such as a hormone imbalance that hurts the heart. Scientists also suspect that because short people have smaller arteries, those could theoretically get clogged quicker with cholesterol and be more easily damaged by any changes in blood pressure.

But Joep Perk, a professor of health sciences at Linnaeus University in Sweden and a spokesman for the European Society of Cardiology, said it was too early to conclude short people had potentially problematic hearts. "We should be very cautious to tell short people they're at risk," he said. "This could unfairly stigmatise them."

He said it was premature for cardiologists to consider height as a risk factor. "We need to understand the mechanism behind it before we can do anything with this information," he said. "This is an interesting observation, but I want to know what I can do for my patients."

Tuula Paajanen, the study's lead author from Tampere University Hospital in Finland, said short people shouldn't be alarmed about the findings. "Height is only one factor (among many) that may contribute to heart disease risk," she said.

Paajanen recommended people focus on other things like not smoking, eating a balanced diet and exercise. "Those are easier to change than your height."


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