Tuesday, February 04, 2014

People slow to react are more likely to die prematurely, study finds

Reaction time has a substantial correlation with IQ so we could just be seeing an IQ effect here. We already know that high IQ people are healthier and live longer.  And low IQ people are much more likely to engage in violence and fighting

Whether you're naked and hungry on the savannah, driving in traffic or at the controls of your favorite video game, being slow to react can get you eaten, injured or splattered across the screen. While we intuitively know this, a new study offers dramatic evidence of how much speed of response still matters: In men and women from ages 20 to 59, slower than average reaction time turned out to be a pretty good predictor of premature death.

The new research, published this week in the journal PLoS One, was large, simple and highly revealing. Between 1988 and 1994, researchers gave 5,134 Americans adults under 60 a very straightforward test of reaction time: The participants, all part of a large federal study of American nutrition and health, were seated at a computer and told to push a button immediately upon seeing a 0 on the screen in front of them. There was no practice period; a participant's average over 50 trials was computed, and he or she had just a few seconds between those 50 trials.

Want to try a similar test of reaction time? Try your hand at this (very fun) game.

The researchers measured the range of reaction times across the group. They computed a "standard deviation" -- a unit of measure that marks the extent to which an individual's performance departs from the group's average. They took note of the "variability" of each participants' response time -- how widely reaction time fluctuated in the course of their 50 tries.

Then they waited close to 15 years to see who in this relatively young group of Americans would die, and of what.

Because the participants had been recruited for an ongoing study of health and nutrition, the researchers had a wealth of health-related information on them. They could use that data to adjust for risk factors such as age, gender and ethnicity.

In all, 378 of the participants died during a follow-up period that averaged 14.6 years -- 104 of cardiovascular deaths and 84 of cancer deaths.

When the researchers -- all from the University of Edinborough -- went back to compare participants' response times with their likelihood of being among the dead, they detected a clear pattern: for those with slow reaction times, each standard deviation that separated an individual's performance from the group's average increased his or her likelihood of dying by 25%.

Those who were slower than the group average by four standard deviations were twice as likely as those whose performance was average to have died over the 15-year follow-up period.

High variability in response time was also linked to a higher risk of death in the study. But those with high variability in response-time also tended to be the same people who response time was slower-than-average.

The authors noted that response time and variability were as powerful at predicting the likelihood of death as was another influential risk factor for death: smoking.

Response speed was much more likely to predict cardiovascular death than it was to predict death by cancer. This suggests that long before a stroke or heart attack fells its victim, the creeping progress of narrowing arteries, inefficient blood flow and weakening hearts might be evident as a slowing of response time, the study authors wrote.


Antioxidants speed lung cancer growth in mice, study finds

Since the foundations of the antioxidant religion are largely in rodent studies, challenges to the religion can reasonably come from that source too

People who smoke or have lung cancer should think twice about taking vitamin supplements, according to a Swedish study Wednesday that showed certain antioxidants may make tumors grow faster.

Lab mice that already had cancer were given vitamin E and a drug called acetylcysteine, which sped the growth of their tumors and made them die faster than mice that did not ingest supplements.

"Antioxidants caused a three-fold increase in the number of tumors and also tumor aggressiveness, and the antioxidants caused the mice to die twice as fast," said study author Martin Bergo of the University of Gothenburg in Sweden.

"If we gave a low dose, tumors increased a little bit. And if we gave a high dose, tumors increased a lot."

Research on human lung cancer cells growing in a lab dish also showed that the antioxidants caused the cells to multiply faster than they would have alone, suggesting the same might happen in human patients.

While more work needs to be done to confirm the effect in people, Bergo urged those with lung cancer, chronic obstructive pulmonary disease and smokers to take caution.

"You can walk around with an undiagnosed lung tumor for a long time," he said.

"If you are in this patient group, then taking extra antioxidants might be harmful and it could speed up the growth of that tumor."

Mixed results from supplement studies

The body produces its own antioxidants to prevent DNA damage from chemicals known as free radicals, but needs more from healthy foods like leafy greens, vegetables and fruits to stay healthy.

However, a large body of research on antioxidant supplements in humans has returned mixed results.

Some studies have suggested that people who take antioxidant supplements actually face a higher risk of cancer than those who do not.

One such study of nearly 30,000 men in Finland, which concluded in 1993, found that smokers who took the antioxidant beta carotene had a higher rate of cancer and greater risk of dying.

Other studies, such as the SELECT trial which enrolled 35,000 US and Canadian men beginning in 2001, found that men who took vitamin E were more likely to get prostate cancer.

"We haven't completely ironed out which vitamins, if any, may prevent cancer and which may cause cancer development or growth," said Benjamin Levy, director of thoracic medical oncology at Mount Sinai Beth Israel Hospital in New York.

"This study may help explain the negative findings from prior clinical lung cancer studies, including the ATBC and SELECT studies," said Levy, who was not involved in the research.

Antioxidants protect tumors, too

Researchers said their findings suggest antioxidants help tumors cut down on harmful free radicals, just as they do in normal cells, allowing the tumors to grow faster.

Free radicals can damage cells and possibly lead to cancer. But free radicals exist in cancer cells, too, explained Bergo.

"So it is also in the tumor's interest to suppress free radicals, and that is what we are doing when we take extra antioxidants—or give it to the mice in this case," he told reporters.

A protein called p53 can sense when DNA has been damaged by the buildup of molecules called reactive oxygen species (ROS).

P53 can stop the growth of the cell and thereby stop the cancer.

When extra antioxidants reduce the level of ROS, this "allows the cancer cells to escape their own defense system," said co-author Per Lindahl from the University of Gothenburg.

Of particular concern is the finding that acetylcysteine increased tumor growth, since the drug is often given to patients with chronic obstructive pulmonary disease (COPD) as a way to help them breathe better and clear mucus from their lungs.

"We think that the use of acetylcysteine in this patient group should probably be carefully evaluated," said Bergo.

He added that researchers are now combing through data registries to find out if COPD patients—including people with chronic bronchitis and emphysema—have higher cancer rates after taking the drug.

The research appears in the journal Science Translational Medicine.


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