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Surprised...is how I felt after reading this study. According to the study, activity levels and exercise in mid-life are not linked to cognitive fitness and dementia later on in life. Instead, higher levels of physical activity and exercise has a beneficial effect on the brain in the short term (e.g., within 2 years or so). This finding of no long-term benefits, but only short-term benefits to the brain from exercise, is contrary to some other (cross-sectional) studies, but is supported by another recent study ("no evidence of a neuroprotective effect of physical activity").

The beauty of this study is that it followed 646 people for 30 years (from a median age of 46 years in 1978 and 77 years in 2008). The negative is that according to this study, physical exercise in mid-life does not seem to delay or prevent the onset of dementia and Alzheimer's later on in life. Eh... From Medical Xpress:

Physical activity in midlife not linked to cognitive fitness in later years, long-term study shows

A study led by Johns Hopkins Bloomberg School of Public Health researchers that tracked activity levels of 646 adults over 30 years found that, contrary to previous research, exercise in mid-life was not linked to cognitive fitness in later yearsThe finding suggests that physical activity may not help maintain cognitive function, or help avoid or delay the onset of the debilitating conditions like dementia and Alzheimer's

The study, which appears online in the Journal of Alzheimer's Disease, did find that activity levels among study participants in the later years were associated with high cognitive function two years later. This supports earlier research findings that exercise may help to maintain cognitive fitness in the short term.

There is no known treatment or cure for Alzheimer's or dementia, syndromes that involves declining memory, confusion and eventually limited ability to perform daily tasks. To date, there are no preventive measures, such as physical exercise, brain games or a diet regimen, that have been proven to help delay or altogether prevent its onset. The researchers undertook the study because of a growing consensus that physical activity levels helps prevent Alzheimer's, however much of the evidence for this thinking is based on cross-sectional studies that compare responses from one group of participants with another at a given point in time or within a very short duration, typically several years..... That's where longitudinal studies, which look at the same group of participants over a long time, are more helpful.

The researchers used data from the Johns Hopkins Precursors study.... The researchers used responses from 1978 through 2008 from 646 participants (598 men, 48 women) to calculate so-called metabolic equivalents, which quantify physical activity levels. Participants were also asked whether they regularly exercise to a sweat. The team administered cognitive tests in 2008, and, using participants' medical records, scored for dementia through 2011. The researchers identified 28, or 4.5 percent of the cohort, to have Alzheimer's.

No physical activity measure in mid-life was associated with late-life cognitive fitness or onset of dementia. The study confirmed findings of other cross-sectional studies, that higher levels of physical activity and exercise measured close in time to the cognitive testing were associated with better cognitive functioning. The authors also looked at whether patterns of change in physical activity levels over the life span were associated with cognitive health and found no relationships.

The idea that exercise might play a role in preventing or limiting Alzheimer's makes sense, the researchers say, because physical activity, at least in mouse models, has shown less accumulation of B-amyloid plaques, which are thought to play a role in dementia, including Alzheimer's. In addition, physical activity improves blood flow to the brain, which is linked to better cognitive performance. This may explain why studies find that exercise may contribute to cognitive fitness in the short term.

 Once again a great reason to exercise - a study found that adults with the highest levels of weekly physical activity had the longest telomeres, which are markers of overall health and aging. Think of it this way: we all age, but some people seem young for their age, while others seem old for their age. This study looked at differences among groups of people at the cellular level.

The multi-year study looked at both physical activity levels of 5,823 adults and their telomeres. The adults provided DNA samples, from which the researchers measured telomere length. Telomeres are "protein caps positioned at the end of chromosomes". Aging causes telomeres to shorten and results in gradual cell deterioration - thus they are good markers of our biological age, that is, how we're aging (rather than just our chronological age). Study author Larry A. Tucker said “We know that, in general, people with shorter telomeres die sooner and are more likely to develop many of our chronic diseases. It's not perfect, but it's a very good index of biological aging.”

What causes telomeres to shrink faster?  Telomere shortening  can be hastened by things that result in inflammation and oxidative stress, such as obesity, smoking, poor diet, type 2 diabetes, and low socioeconomic levels. On the other hand, this study found that adults with high levels of physical activity had significantly longer telomeres. The longer telomeres found in the active adults reduced cellular aging by about 9 years, as compared to those adults who were sedentary or had low to medium levels of physical activity. Nine years less of biological aging is a lot! The shortest telomeres were in sedentary people.

How much physical activity should one aim for? The study found that activity levels in the study were measured in MET-minutes (metabolic equivalent minutes) - which can sound confusing, but can be achieved by incorporating exercise into daily routines, as well as also doing vigorous activities or exercises. In the present study, men had to attain >1887 MET-minutes per week and women >1375 to be included in the category with the highest activity levels (longest telomeres). It does mean several hours a week of physical activity, which can include gardening, bicycling, walking, vacuuming, exercising, running, etc. From Science Daily:

High levels of exercise linked to nine years of less aging at the cellular level

Despite their best efforts, no scientist has ever come close to stopping humans from aging. But new research from Brigham Young University reveals you may be able to slow one type of aging -- the kind that happens inside your cells. As long as you're willing to sweat. "Just because you're 40, doesn't mean you're 40 years old biologically," Tucker said. "We all know people that seem younger than their actual age. The more physically active we are, the less biological aging takes place in our bodies."

The study, published in the medical journal Preventive Medicine, finds that people who have consistently high levels of physical activity have significantly longer telomeres than those who have sedentary lifestyles, as well as those who are moderately activeTelomeres are the protein endcaps of our chromosomes. They're like our biological clock and they're extremely correlated with age; each time a cell replicates, we lose a tiny bit of the endcaps. Therefore, the older we get, the shorter our telomeres.

Exercise science professor Larry Tucker found adults with high physical activity levels have telomeres with a biological aging advantage of nine years over those who are sedentary, and a seven-year advantage compared to those who are moderately active. To be highly active, women had to engage in 30 minutes of jogging per day (40 minutes for men), five days a week.

Tucker analyzed data from 5,823 adults who participated in the CDC's National Health and Nutrition Examination Survey, one of the few indexes that includes telomere length values for study subjects....His study found the shortest telomeres came from sedentary people -- they had 140 base pairs of DNA less at the end of their telomeres than highly active folks. Surprisingly, he also found there was no significant difference in telomere length between those with low or moderate physical activity and the sedentary people.

 A new study found differences in gut microbes between active women (they exercised at least the recommended amount) and those that are sedentary. When the gut bacteria were analyzed with modern tests (genetic sequencing) the active women had more of the health promoting beneficial bacteria such as Faecalibacterium prausnitzii, Roseburia hominis, and Akkermansia muciniphila than the sedentary women. The sedentary women also had some bacterial species not seen in the active women. The researchers said that exercise "modifies the composition of gut microbiota" (the gut microbes) in a way beneficial for health.

And what is the recommended minimal amount of exercise? The World Health Organization recommends at least 3 days of exercise per week for 30 minutes at a moderate intensity. Note that exercise can mean doing exercises, but it can also include walking briskly, intense housework (scrubbing, vacuuming with lots of bending, etc.), gardening (digging, raking, etc), or shoveling snow, etc. In this study the group of active women had at least 3 hours of physical exercise per week. Note that a sedentary lifestyle is associated with a high incidence of chronic diseases such as cardiovascular disease, cancer and diabetes, while physical exercise or activity has metabolic and immune health benefits (prevents disease).

But...reading the full study, the research also showed that the active group ate more fruits and vegetables - which we know has an effect on the gut microbiome and feeds beneficial bacteria. Although the diets of the 2 groups of women were similar in total carbohydrates, protein and fat content eaten, the active women ate more fruits, vegetables, and fiber, and the sedentary group ate more processed meat. So it looks like both exercise and a good amount of fruits and vegetables may be important for nurturing beneficial bacteria. By the way, the 3 species of beneficial bacteria mentioned currently are not found in any probiotic supplements on the market. (Earlier posts on the beneficial F. prausnitzii and Akkermansia muciniphila). From PLoS ONE:

Differences in gut microbiota profile between women with active lifestyle and sedentary women

Physical exercise is a tool to prevent and treat some of the chronic diseases affecting the world’s population. A mechanism through which exercise could exert beneficial effects in the body is by provoking alterations to the gut microbiota, an environmental factor that in recent years has been associated with numerous chronic diseases. Here we show that physical exercise performed by women to at least the degree recommended by the World Health Organization can modify the composition of gut microbiota. Using high-throughput sequencing of the 16s rRNA gene, eleven genera were found to be significantly different between active and sedentary women. Quantitative PCR analysis revealed higher abundance of health-promoting bacterial species in active women, including Faecalibacterium prausnitzii, Roseburia hominis and Akkermansia muciniphila. Moreover, body fat percentage, muscular mass and physical activity significantly correlated with several bacterial populations. In summary, we provide the first demonstration of interdependence between some bacterial genera and sedentary behavior parameters, and show that not only does the dose and type of exercise influence the composition of gut microbiota, but also the breaking of sedentary behavior.

Sedentary lifestyle is associated with a high incidence of chronic diseases such as cardiovascular disease, cancer and diabetes. Physical exercise is a powerful preventative and treatment intervention that is known to be effective in generating metabolic and immune health benefits. The gut microbiota is essential for processing dietary components and has a major role in shaping the immune system.... Dysbiosis or imbalance in gut microbiota has been associated with many diseases, among which are ulcerative colitis, Crohn's disease, colon cancer, metabolic syndrome, type I and type II diabetes, cardiovascular disease, allergy, asthma, eczema and autism.....Several studies in experimental models have addressed the relationship between gut microbiota composition and physical exercise....Collectively, these findings indicate that modulation of the microbiota by exercise depends not only on the physiological state of the individual, but also on the diet.

A total of 15 phyla were detected, in order of presence: Bacteroidetes (54%), Firmicutes (44%), Proteobacteria (0.96%), Tenericutes (0.39%), Verrucomicrobia (0.11%), Euryarchaeota (0.08%), Actinobacteria (0.07%), Lentisphaerae (0.06%), Cyanobacteria (0.050%), Spirochaetes (0.04%), Fusobacteria (0.014%), Elusimicrobia (0.009%), Synergistetes (0.007%), kTM7 (0.003%), and Acidobacteria (0.0001%). Acidobacteria (2 subjects), Elusimicrobia (2 subjects) and Spirochaetes (2 subjects) phyla were detected only in sedentary subjects.... At the genus level, there were significant differences in eleven genera: Bifidobacterium, Barnesiellaceae, Odoribacter, Paraprevotella, Turicibacter, Clostridiales, Coprococcus, Ruminococcus, and two unknown genera of Ruminococcaceae family. Given the importance of some bacterial species in health, the presence of Bifidobacterium longum, Faecalibacterium prausnitzii, Roseburia hominis, Akkermansia muciniphila was measured by qPCR. Analyses revealed a more significant abundance of F. prautznnii, R. hominis and A. muciniphila in active than in sedentary women.

Among all the genera studied, the abundance of eleven of them was significantly different between the active and sedentary group, with Paraprevotella and an unclassified genus of the Desulfovibrionaceae family specifically associated with sedentarism parameters, while the remaining genera where largely associated with diet parameters.....Nonetheless, as exercise and diet often go hand in hand, an active lifestyle is frequently associated with a high consumption of fruits and vegetables, whereas sedentarism is associated with the consumption of high-calorie and fatty foods. Indeed, exercise interventions in human populations have resulted in an improvement in diet habits. Although the diets were similar in our study regarding total carbohydrates, protein and fat content, significant differences were observed for fiber (higher in the active group) and processed meat (higher in the sedentary group).

 Worried about whether being physically active just on weekends can make a difference in health if the rest of the week is spent sitting all day? Well, there is good news! Being a "weekend warrior" (one who exercises or is active only one or two days a week) may also offer health benefits according to a new study (associated with lower death rates from all causes, cancer, and cardiovascular disease).

Current government guidelines recommend at least 150 minutes per week of moderate-intensity activity (such as brisk walking or tennis), or at least 75 minutes per week of vigorous activity (such as jogging or swimming laps), or equivalent combinations of moderate and vigorous physical activity. From Science Daily:

'Weekend warriors' have lower risk of death from cancer, cardiovascular disease

Physical activity patterns characterized by just one or two sessions a week may be enough to reduce deaths in men and women from all causes, cardiovascular disease (CVD) and cancer, regardless of adherence to physical activity guidelines, a new study of over 63,000 adults reports. The finding suggests that less frequent bouts of activity, which might fit more easily into a busy lifestyle, offer significant health benefits, even in the obese and those with medical risk factors.

Regular physical activity is associated with lower risks of death from all causes, cardiovascular disease and cancer, and has long been recommended to control weight, cholesterol, and blood pressure. The World Health Organization recommends that adults do at least 150 minutes per week of moderate-intensity activity, or at least 75 minutes per week of vigorous-intensity activity, or equivalent combinations.

But research is yet to establish how the frequency and total weekly dose of activity might best be combined to achieve health benefits. For example, individuals could meet current guidelines by doing 30 minutes of moderate-intensity physical activity five days of the week or 75 minutes of vigorous-intensity physical activity on just one day of the week. Those who do all their exercise on one or two days of the week are known as 'weekend warriors'. 

 Looks like exercise, even 20 minutes of moderate activity such as brisk walking, has beneficial anti-inflammatory health effects. Inflammation is part of the body's normal immune response - it is the body's attempt to heal itself after an injury and tissue damage, and to defend itself against infection from foreign invaders, such as viruses and bacteria. However, chronic inflammation (e.g., what can occur in obesity, diabetes, and poor lifestyle) can lead to serious health issues and is linked to cancer, heart disease, etc. So lowering chronic (systemic) inflammation is good. From Science Daily:

Exercise ... It does a body good: 20 minutes can act as anti-inflammatory

It's well known that regular physical activity has health benefits, including weight control, strengthening the heart, bones and muscles and reducing the risk of certain diseases. Recently, researchers at University of California San Diego School of Medicine found how just one session of moderate exercise can also act as an anti-inflammatory. The findings have encouraging implications for chronic diseases like arthritis, fibromyalgia and for more pervasive conditions, such as obesity.

The study, recently published online in Brain, Behavior and Immunity, found one 20-minute session of moderate exercise can stimulate the immune system, producing an anti-inflammatory cellular response. The brain and sympathetic nervous system -- a pathway that serves to accelerate heart rate and raise blood pressure, among other things -- are activated during exercise to enable the body to carry out work. Hormones, such as epinephrine and norepinephrine, are released into the blood stream and trigger adrenergic receptors, which immune cells possess. This activation process during exercise produces immunological responses, which include the production of many cytokines, or proteins, one of which is TNF -- a key regulator of local and systemic inflammation that also helps boost immune responses.

The 47 study participants walked on a treadmill at an intensity level that was adjusted based on their fitness level. Blood was collected before and immediately after the 20 minute exercise challenge."Our study shows a workout session doesn't actually have to be intense to have anti-inflammatory effects. Twenty minutes to half-an-hour of moderate exercise, including fast walking, appears to be sufficient," said Hong.

Inflammation is a vital part of the body's immune response. It is the body's attempt to heal itself after an injury; defend itself against foreign invaders, such as viruses and bacteria; and repair damaged tissue. However, chronic inflammation can lead to serious health issues associated with diabetes, celiac disease, obesity and other conditions.

  Again, another study showing the importance of lifestyle factors in the development of protein buildups in the brain that are associated with the onset of Alzheimer's disease. Specifically, the study found that each one of several lifestyle factors—a healthy body mass index, physical activity and a Mediterranean diet, were linked to lower levels of plaques and tangles on brain scans in people who already had mild memory changes, (but not dementia). Other posts discussing Mediterranean diet and brain health (brain volume, etc.) are here, here, and here. Activity levels and brain health posts are here, here, and here. From Medical Xpress:

Diet and exercise can reduce protein build-ups linked to Alzheimer's

A study by researchers at UCLA's Semel Institute for Neuroscience and Human Behavior has found that a healthy diet, regular physical activity and a normal body mass index can reduce the incidence of protein build-ups that are associated with the onset of Alzheimer's disease.

In the study, 44 adults ranging in age from 40 to 85 (mean age: 62.6) with mild memory changes but no dementia underwent an experimental type of PET scan to measure the level of plaque and tangles in the brain. Researchers also collected information on participants' body mass index, levels of physical activity, diet and other lifestyle factors. Plaque, deposits of a toxic protein called beta-amyloid in the spaces between nerve cells in the brain; and tangles, knotted threads of the tau protein found within brain cells, are considered the key indicators of Alzheimer's.

The study found that each one of several lifestyle factors—a healthy body mass index, physical activity and a Mediterranean diet—were linked to lower levels of plaques and tangles on the brain scans. (The Mediterranean diet is rich in fruits, vegetables, legumes, cereals and fish and low in meat and dairy, and characterized by a high ratio of monounsaturated to saturated fats, and mild to moderate alcohol consumption.)

"The fact that we could detect this influence of lifestyle at a molecular level before the beginning of serious memory problems surprised us," said Dr. David Merrill, the lead author of the study, which appears in the September issue of the American Journal of Geriatric Psychiatry.

Earlier studies have linked a healthy lifestyle to delays in the onset of Alzheimer's. However, the new study is the first to demonstrate how lifestyle factors directly influence abnormal proteins in people with subtle memory loss who have not yet been diagnosed with dementia, Merrill said. Healthy lifestyle factors also have been shown to be related to reduced shrinking of the brain and lower rates of atrophy in people with Alzheimer's."The study reinforces the importance of living a healthy life to prevent Alzheimer's, even before the development of clinically significant dementia," Merrill said. 

 Get active, really active, to reduce your risk for 5 diseases: breast cancer, colon cancer, heart disease, and ischemic stroke. Instead of the 150 minutes of brisk walking or 75 minutes per week of running (which is equal to the 600 metabolic equivalent (MET) minutes now recommended by the World Health Organization), this study found that much more exercise is needed for best health results.

This study (which was a review and analysis of 174 studies) found that there is a dose-response effect, with the most reduction in the risk of the 5 conditions by getting 3000 to 4000 MET minutes per week. This sounds like a lot, but the researchers  point out that this can be achieved by incorporating exercise into your daily routines. The researchers write: "A person can achieve 3000 MET minutes/week by incorporating different types of physical activity into the daily routine—for example, climbing stairs 10 minutes, vacuuming 15 minutes, gardening 20 minutes, running 20 minutes, and walking or cycling for transportation 25 minutes on a daily basis would together achieve about 3000 MET minutes a week."

So start thinking creatively about how to increase exercise or activity into your daily life, especially moderate or vigorous intensity activity. For example, park your car far from the store door, or better yet, bicycle or walk to the store from home. From Medscape:

Get Moving: High Physical-Activity Level Reduces Risk of 5 Diseases

High levels of physical activity can reduce the risk for five major diseases, including type 2 diabetes, new research shows. Findings from the systematic review and meta-analysis were published online ....The data, from a total 174 studies comprising 149,184,285 total person-years of follow-up, suggest that the more total regular daily physical activity one engages in — including recreation, transportation, occupational activity, and/or daily chores — the lower the risks for breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke.

However, significant reductions in those conditions were seen only with total activity levels considerably higher than the minimum 600 metabolic equivalent (MET) minutes per week recommended by the World Health Organization for health benefits. That 600 METs equates to about 150 minutes/week of brisk walking or 75 minutes/week of running. (A MET is defined as the ratio of the metabolic rate during that activity to the metabolic rate when resting.) Risks of the five conditions dropped significantly with an increase in MET minutes per week from 600 to 3000 to 4000, with less additive benefit seen above that level.

For reference, the authors say, "a person can achieve 3000 MET minutes/week by incorporating different types of physical activity into the daily routine — for example, climbing stairs 10 minutes, vacuuming 15 minutes, gardening 20 minutes, running 20 minutes, and walking or cycling for transportation 25 minutes on a daily basis would together achieve about 3000 MET minutes a week." "This amount might seem a bit large, but this is about total activity across all domains of life.…For people who currently don't exercise, clinicians could encourage them to incorporate physical activity into their daily routines, [such as] turning household chores into exercise. 

Another recent meta-analysis of trials involving more than one million individuals indicated that an hour of moderate-intensity activity, such as brisk walking or cycling, offsets the health risks of 8 hours of sitting. The message that physical inactivity is a killer — leading to 5.3 million premature deaths annually worldwide, which is as many as caused by smoking and twice as many as associated with obesity, has been emerging over the past few years, with warnings that "sitting is the new smoking."

This new research is the first meta-analysis to quantify the dose-response association between total physical activity across all domains and the risk of five chronic diseases. The 174 prospective cohort studies included 35 for breast cancer, 19 for colon cancer, 55 for diabetes, 43 for ischemic heart disease, and 26 for ischemic stroke. (Some included more than one end point.)....Higher levels of total physical activity were associated with lower risks of all five outcomes.

With the development of diabetes, for example, compared with no physical activity, those with 600 MET minutes per week (the minimum recommended level of activity) had a 2% lower risk. That risk reduction jumped by an additional 19% with an increase from 600 to 3600 METs/week. Gains were smaller above that, with the increase of total activity from 9000 to 12,000 MET minutes/week yielding only an additional 0.6% diabetes reduction.

Overall, compared with insufficiently active individuals (total activity < 600 MET minutes/week), the risk reduction for those in the highly active category (≥ 8000 MET minutes/week) was 14% for breast cancer; 21% for colon cancer; 28% for diabetes; 25% for ischemic heart disease; and 26% for ischemic stroke

 Credit: Medscape

 Get out there and start getting active NOW - the earlier you start in life, the better for your brain decades later. All physical activity or exercise is good, including regular walks. From Medical Xpress:

Regular exercise protects against cognitive decline in later years

Regular exercise in middle age is the best lifestyle change a person can make to prevent cognitive decline in the later years, a landmark 20-year study has found.

University of Melbourne researchers followed 387 Australian women from the Women's Healthy Ageing Project for two decades. The women were aged 45 to 55-years-old when the study began in 1992. The research team made note of their lifestyle factors, including exercise and diet, education, marital and employment status, number of children, mood, physical activity and smoking....They were also asked to learn a list of 10 unrelated words and attempt to recall them half an hour later, known as an Episodic Verbal Memory test.

When measuring the amount of memory loss over 20 years, frequent physical activity, normal blood pressure and high good cholesterol were all strongly associated with better recall of the words. Study author Associate Professor Cassandra Szoeke, who leads the Women's Healthy Ageing Project, said once dementia occurs, it is irreversible. "In our study more weekly exercise was associated with better memory." 

"We now know that brain changes associated with dementia take 20 to 30 years to develop," Associate Professor Szoeke said. "The evolution of cognitive decline is slow and steady, so we needed to study people over a long time period. We used a verbal memory test because that's one of the first things to decline when you develop Alzheimer's Disease."
Regular exercise of any type, from walking the dog to mountain climbing, emerged as the number one protective factor against memory loss. Asoc Prof Szoeke said that the best effects came from cumulative exercise, that is, how much you do and how often over the course of your life.  (Original study)

Another new study about lifestyle and the risk of cancer. Many earlier studies have established some lifestyle factors that increase cancer risk: smoking, alcohol use, obesity, and physical inactivity. In this study the researchers found that about 20% to 40% of cancer cases and about half of cancer deaths can be potentially prevented through lifestyle modification. For some cancers the the effect is even larger - for example, approximately 80% to 90% of lung cancer deaths could be avoided if Americans adopted the lifestyle of the low-risk group, mainly by quitting smoking. For other cancers, from 10% to 70% of deaths could be prevented. Bottom line: making some lifestyle changes could change a person's cancer risk. Science Daily:

Can a healthy lifestyle prevent cancer?

A large proportion of cancer cases and deaths among U.S. individuals who are white might be prevented if people quit smoking, avoided heavy drinking, maintained a BMI between 18.5 and 27.5, and got moderate weekly exercise for at least 150 minutes or vigorous exercise for at least 75 minutes, according to a new study published online by JAMA Oncology. Cancer is a leading cause of death in the United States.

Mingyang Song, M.D., Sc.D., of Massachusetts General Hospital, Harvard Medical School and the Harvard T.H. Chan School of Public Health, Boston, and Edward Giovannucci, M.D., Sc.D., of the Harvard T.H. Chan School of Public Health and Harvard Medical School, Boston, analyzed data from two study groups of white individuals to examine the associations between a "healthy lifestyle pattern" and cancer incidence and death.

A "healthy lifestyle pattern" was defined as never or past smoking; no or moderate drinking of alcohol (one or less drink a day for women, two or less drinks a day for men); BMI of at least 18.5 but lower than 27.5; and weekly aerobic physical activity of at least 150 minutes moderate intensity or 75 minutes vigorous intensity. Individuals who met all four criteria were considered low risk and everyone else was high risk. The study included 89,571 women and 46,399 men; 16,531 women and 11,731 had a healthy lifestyle pattern (low-risk group) and the remaining 73,040 women and 34,608 men were high risk.

The authors suggest about 20 percent to 40 percent of cancer cases and about half of cancer deaths could potentially be prevented through modifications to adopt the healthy lifestyle pattern of the low-risk group.The authors note that including only white individuals in their PAR estimates may not be generalizable to other ethnic groups but the factors they considered have been established as risk factors in diverse ethnic groups too.

 A recent study pooled the data from over a million Europeans and Americans and found that higher levels of leisure-time physical activity was associated with a reduced risk of developing cancer in 13 of the 26 cancers looked at. For that group of 13 cancers, the cancer risk reduction ranged from 10% to 42%. And most of these associations (leisure-time physical activity and lower risk of cancer) were evident regardless of body size or smoking history. Bottom line: getting active may lower your cancer risk. From Science Daily:

Physical activity associated with lower risk for many cancers

Higher levels of leisure-time physical activity were associated with lower risks for 13 types of cancers, according to a new study published online by JAMA Internal Medicine. Physical inactivity is common, with an estimated 51 percent of people in the United States and 31 percent of people worldwide not meeting recommended physical activity levels. Any decrease in cancer risk associated with physical activity could be relevant to public health and cancer prevention efforts.

Steven C. Moore, Ph.D., M.P.H., of the National Cancer Institute, Bethesda, Md., and coauthors pooled data from 12 U.S. and European cohorts (groups of study participants) with self-reported physical activity (1987-2004). They analyzed associations of physical activity with the incidence of 26 kinds of cancer.The study included 1.4 million participants and 186,932 cancers were identified during a median of 11 years of follow-up.

The authors report that higher levels of physical activity compared to lower levels were associated with lower risks of 13 of 26 cancers: esophageal adenocarcinoma (42 percent lower risk); liver (27 percent lower risk); lung (26 percent lower risk); kidney (23 percent lower risk); gastric cardia (22 percent lower risk); endometrial (21 percent lower risk); myeloid leukemia (20 percent lower risk); myeloma (17 percent lower risk); colon (16 percent lower risk); head and neck (15 percent lower risk), rectal (13 percent lower risk); bladder (13 percent lower risk); and breast (10 percent lower risk). Most of the associations remained regardless of body size or smoking history, according to the article. Overall, a higher level of physical activity was associated with a 7 percent lower risk of total cancer.

Physical activity was associated with a 5 percent higher risk of prostate cancer and a 27 percent higher risk of malignant melanoma, an association that was significant in regions of the U.S. with higher levels of solar UV radiation but not in regions with lower levels, the results showed.

The authors note the main limitation of their study is that they cannot fully exclude the possibility that diet, smoking and other factors may affect the results. Also, the study used self-reported physical activity, which can mean errors in recall."These findings support promoting physical activity as a key component of population-wide cancer prevention and control efforts," the authors conclude.