Being physically fit may be as good for you as not smoking
News and notes about science
Being in shape may be as important to a long life as not smoking, according to an interesting new study of the links between fitness and mortality.
The study also explores whether there is any ceiling to the benefits of fitness — whether, in essence, you can exercise too much. The answer, it found, is a reassuring no.
At this point, we should not be surprised to hear that people who exercise and have high aerobic endurance tend to live longer than those who are sedentary and out of shape. A large body of past research has linked exercise with longevity and indicated that people who work out tend also to be people with lengthy, healthy lives.
But much of this research relied on asking people about their exercise routines, a practice that is known to elicit unreliable answers.
So for the new study, which was published last month in JAMA Network Open, a group of researchers and physicians at the Cleveland Clinic decided to look for more objective ways to measure the relationship between endurance and longevity.
Because most of the researchers also are avid exercisers and even competitive athletes, they hoped to learn, too, whether people can overdo exercise and potentially shorten their life spans.
Helpfully, they had a trove of data at hand in the records of hundreds of thousands of men and women who had completed treadmill stress tests at the clinic.
These stress tests, which sometimes are part of standard yearly checkups and other times are ordered by physicians to check for cardiac or other health problems, involve someone jogging on a treadmill at a progressively intense pace until, basically, he or she cannot.
Based on the results, technicians can determine people’s aerobic fitness.
Now, the researchers turned to this database and pulled records for 122,007 middle-age or older men and women.
They grouped the people by fitness, from those who were in the bottom quarter of fitness, to those who were below average, above average or highly fit, essentially in the top 25 percent of fitness.
The researchers also marked off a small group in the top 2 percent or so of endurance and categorized them as having “elite” fitness.
Then the researchers checked death records for the decade after people had completed their stress tests.
They found that some of the men and women had died and also that there were strong correlations between fitness and mortality. The greater someone’s fitness, the less likely he or she was to have died prematurely and vice versa, the numbers showed.
This correlation held true at every level of fitness, the researchers found. People with the lowest fitness were more likely to die early than those with below-average fitness, while those with high fitness lived longer than those whose fitness was above average.
Even at the loftiest reaches of endurance, the advantage held, the data showed. The 2 percent of the people with elite fitness lived longer than those with high fitness and were about 80 percent less likely to die prematurely than the men and women with the lowest endurance.
“We did not see any indication that you can be too fit,” said Dr. Wael Jaber, the study’s senior author and a cardiologist at the Cleveland Clinic Lerner College of Medicine.
More surprising, when the researchers compared the longevity benefits of endurance with those of other health factors, fitness held up well.
People in this database who smoked or had heart disease were more likely to die young than those who did not, the researchers found, as they had expected. But the numerical risks were about the same as the ones associated with being unfit. In other words, being out of shape increased someone’s risk of dying early as much as smoking did.
Jaber cautions, however, that these numbers can be misinterpreted. The clinic’s medical records noted only if someone had ever smoked, not for how many years or how frequently, making risk assessments difficult.
Nor do the correlations suggest that being fit somehow balances out or reduces the health risks of smoking, Jaber said. “Fitness is very good for you and so, obviously, is not smoking,” he said.
The study has other caveats, including the confounding role of genes, which strongly influence fitness. Some of the apparent longevity benefits of being in shape may be from having the right parents, Jaber said.
Socioeconomic status and other factors also probably play a role. People who show up for stress testing at the Cleveland Clinic may have resources that are not shared by everyone, including good insurance and an interest in health.
Perhaps most fundamentally, the study did not look directly at exercise, only fitness, and so cannot tell us how much we should move to extend our lives.
But the findings are tantalizing, Jaber said. “We know from other research that you can increase fitness with exercise,” he said. “So I think we can say, based on this study and others, that it is a very good idea to exercise if you hope for a long and healthy life.”
— Gretchen Reynolds
Do high-cholesterol foods raise your cholesterol?
Foods high in cholesterol, like eggs or cheese, can raise blood cholesterol levels, though the effect is relatively modest and varies from person to person. The best evidence available suggests that saturated fat, rather than dietary cholesterol per se, is the major contributor to serum cholesterol.
In 1991, The New England Journal of Medicine described the case of an 88-year-old man who ate 25 eggs a day for at least 15 years and had normal cholesterol levels and apparently normal arteries. This report challenged a central dogma of medicine: namely, that dietary cholesterol leads to elevated serum cholesterol and atherosclerosis. That belief arose in 1913, when Russian scientist Nikolai Anichkov observed that rabbits developed atherosclerosis after being fed a high-cholesterol diet.
Over the years, the association between diet and atherosclerotic plaque grew, but controversy grew as well. Critics noted that rabbits do not consume cholesterol in the wild, and humans do not consume cholesterol in isolation. The vast majority of foods that are high in cholesterol, like steak or butter, are also high in saturated fats. Notable exceptions to this rule are egg yolks and shellfish, such as shrimp, lobster and crab.
In 1965, a landmark Harvard study — one which could not be replicated today because of evolving ethical standards, as it was performed on schizophrenic patients confined to a mental hospital — showed that saturated fat exerted a greater effect on serum cholesterol than dietary cholesterol did. Subsequent studies supported this conclusion, including the 20-year Western Electric Study of 1,900 men from 1981 and an analysis of 395 experiments that appeared in the British Medical Journal in 1997.
Ultimately, the weight of the evidence led to changes in recommendations. In 2013, the American Heart Association stated, “There is insufficient evidence to determine whether lowering dietary cholesterol reduces LDL-C,” or “bad” cholesterol.” More recently, the Dietary Guidelines Advisory Committee, whose recommendations inform U.S. Department of Agriculture policy, dropped its previous recommendation to limit dietary cholesterol, advising that “cholesterol is not a nutrient of concern for overconsumption.”
It should be emphasized that there is great individual variation in the response to dietary cholesterol. Some people are like the 88-year-old man described above and are able to maintain a normal serum cholesterol despite a high intake of dietary cholesterol. Others are more like Anichkov’s rabbits, and their serum cholesterol levels rise in response to high levels of dietary cholesterol.
— Richard Klasco, M.D.
Effective alarm: Mom’s voice
A mother’s recorded voice will wake a child and get him out the room much faster than a standard smoke alarm, a randomized trial has found.
Researchers recruited 176 5- to 12-year-olds to test alarms. They taught the children a simulated escape procedure: Get out of bed at the alarm, walk to the door and leave the room.
They monitored the children with EEG electrodes until they entered a deep stage of sleep. Then they set off either a standard tone alarm or one of three versions of the mother’s recorded voice shouting instructions and the child’s name.
The study, in the Journal of Pediatrics, found that the tone alarm woke the children about 50 percent of the time, and it took them an average of nearly five minutes to get out of the room.
With the mother’s voice — shouting names, instructions or both — almost 90 percent of the children awoke and were out of the room in an average of less than 30 seconds.
The lead author, Dr. Gary A. Smith, director of the Center for Injury Research and Policy at Nationwide Children’s Hospital in Columbus, Ohio, wondered whether it had to be the mother’s voice or whether any human voice would work as well.
“What we really want,” he said, “is an alarm optimized for kids that will work for all age groups.”
— Nicholas Bakalar