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It's reassuring to see that there are positive things one can do to maintain brain health as one ages. With normal aging, the brain typically shrinks a little with each passing decade  - starting from about the age of 40. But one recent Australian study, which reviewed the results of many other studies, found that exercise slows down this shrinkage in humans, specifically in the left hippocampus. That is, that aerobic exercise had a significant positive effect on the volume of the left hippocampus. This matches the result of animal studies.

The researchers pointed out that some studies found increases also in other parts of the human brain from exercise (e.g. in the white matter), but that they did not look at and review those studies. [See posts on research.] The good news is that positive effects were from exercise programs generally lasting less than 12 months. But it is unknown which type of exercise is best, or whether it is general "activity level and movement" that is most important. Bottom line: Get out there and move, move, move for brain health. And for cardiorespiratory fitness. It's all linked and it's all good. From Medical Xpress:

Exercise maintains brain size, new research finds

Aerobic exercise can improve memory function and maintain brain health as we age, a new Australian-led study has found. In a first of its kind international collaboration, researchers from Australia's National Institute of Complementary Medicine at Western Sydney University and the Division of Psychology and Mental Health at the University of Manchester in the UK examined the effects of aerobic exercise on a region of the brain called the hippocampus, which is critical for memory and other brain functions.

Brain health decreases with age, with the average brain shrinking by approximately five per cent per decade after the age of 40. Studies in mice and rats have consistently shown that physical exercise increases the size of the hippocampus but until now evidence in humans has been inconsistent.

The researchers systematically reviewed 14 clinical trials which examined the brain scans of 737 people before and after aerobic exercise programs or in control conditions. The participants included a mix of healthy adults, people with mild cognitive impairment such as Alzheimer's and people with a clinical diagnosis of mental illness including depression and schizophrenia. Ages ranged from 24 to 76 years with an average age of 66. The researchers examined effects of aerobic exercise, including stationary cycling, walking, and treadmill running. The length of the interventions ranged from three to 24 months with a range of 2-5 sessions per week.

Overall, the results – published in the journal NeuroImage– showed that, while exercise had no effect on total hippocampal volume, it did significantly increase the size of the left region of the hippocampus in humans.

"When you exercise you produce a chemical called brain-derived neurotrophic factor (BDNF), which may help to prevent age-related decline by reducing the deterioration of the brain," Mr Firth said. "Our data showed that, rather than actually increasing the size of the hippocampus per se, the main 'brain benefits' are due to aerobic exercise slowing down the deterioration in brain size. In other words, exercise can be seen as a maintenance program for the brain.".... Interestingly, physical exercise is one of the very few 'proven' methods for maintaining brain size and functioning into older age.

So you finally lost weight by diligently dieting, but now the issue is how to keep the weight from creeping back up again. Keeping strict watch over what you eat (basically continuing to diet)? Or exercising? Or...? Another issue muddying the waters is that a big weight loss also lowers the metabolism rate - something that occurred to former participants of the reality TV show The Biggest Loser. They lost enormous amounts of weight during the 30 week competition (over 100 pounds on average), but 6 years later much of the weight was regained, and they were burning hundreds fewer calories each day at rest. So they had become metabolically much slower over time.

A study looking at 14 former participants of The Biggest Loser 6 years after the show found that a large persistent increase in physical activity was essential for long-term maintenance of weight loss. Those who regained the least weight were the most active, and vice versa. On the other hand, food intake (keeping calorie intake low) wasn't the most important. How much of an increase in physical activity was needed to maintain the weight loss? Researchers found that an increase of about 80 minutes of daily moderate activity (such as brisk walking) or 35 minutes of daily vigorous activity was needed. From Medscape:

The Biggest Loser: Physical Exertion Is Key to Keeping Weight Off

Persistent increased physical activity is likely essential for long-term maintenance of weight loss, new research from participants in the US TV reality show The Biggest Loser suggests.... Using objective measures for both energy intake and physical activity in 14 former Biggest Loser contestants 6 years after they participated in the competition, Dr Kerns and colleagues found that those who had regained the least weight were the most active, and vice versa. Food intake, on the other hand, had very little effect on long-term weight-loss maintenance.

Asked to comment, Eric Ravussin, PhD, Boyd Professor at Louisiana State University, Baton Rouge, and coeditor of Obesity, told Medscape Medical News that the data align with those of follow-ups to major trials — including the Diabetes Prevention Program and the Action for Health Diabetes (Look AHEAD) study as well as with the National Weight Control Registry — of thousands of people who have lost at least 30 pounds and kept them off for at least a year. "The successful losers…all report high levels of physical activity" for weight maintenance, in contrast to weight loss, for which caloric deficit plays a far greater role, Dr Ravussin noted.

The reason for the difference between what works for weight loss vs maintenance, he said, probably has a lot to do with metabolic adaptation. This was the subject of another Biggest Loser paper published in Obesity in 2016, in which a person's metabolism slows down in response to a large drop in weight, making weight-loss maintenance difficult without an extra "push" from exercise, he explained.

The subjects in the new study were 14 participants with class III obesity who participated in a single season of The Biggest Loser, during which they underwent an intensive 30-week diet and exercise program and lost an average of 60 kg. Most regained weight after the program ended, although the degree of regain was highly variable. The median weight loss after 6 years was 13%. Seven subjects above the median weighed 24.9% less than baseline (maintainers) while the seven below the line (regainers) weighed 1.1% above their baseline. The maintainers had significantly greater increases in physical activity from baseline compared with the regainers..... that 35 minutes a day of intensive exercise, or 80 minutes of moderate activity, would roughly approximate the calorie expenditures among the maintainers.

A newly published study suggests that exercising an hour or more per week could lower the incidence of depression. The study followed 33,000 adults in Norway  for 11 years, and found that an hour or more of weekly exercise was associated with 12% fewer cases of developing depression. But note that it didn't prevent anxiety. Interestingly, the researchers found that "regular leisure-time exercise of any intensity" had these positive effects - it doesn't have to be aerobic or incredibly strenuous exercise. Exercise is associated with a number of biological changes that could have an impact on mental health. From Science Daily:

One hour of exercise a week can prevent depression

A landmark study led by the Black Dog Institute has revealed that regular exercise of any intensity can prevent future depression -- and just one hour can help. Published in the American Journal of Psychiatry, the results show even small amounts of exercise can protect against depression, with mental health benefits seen regardless of age or gender.

In the largest and most extensive study of its kind, the analysis involved 33,908 Norwegian adults who had their levels of exercise and symptoms of depression and anxiety monitored over 11 years. The international research team found that 12 percent of cases of depression could have been prevented if participants undertook just one hour of physical activity each week.

A healthy cohort of participants was asked at baseline to report the frequency of exercise they participated in and at what intensity: without becoming breathless or sweating, becoming breathless and sweating, or exhausting themselves. At follow-up stage, they completed a self-report questionnaire (the Hospital Anxiety and Depression Scale) to indicate any emerging anxiety or depression.

Results showed that people who reported doing no exercise at all at baseline had a 44% increased chance of developing depression compared to those who were exercising one to two hours a week. However, these benefits did not carry through to protecting against anxiety, with no association identified between level and intensity of exercise and the chances of developing the disorder. [Original article.]

OK everyone - even if you sit all day at a desk job, the research is clear: try to get up and stretch or move a little every 30 minutes. Researchers followed middle-aged and older adults over a 5 1/2 year period and found that total sitting time (sedentary behavior) and prolonged, uninterrupted sedentary behavior were associated with in increased risk for death from any cause (all-cause mortality). But..adults who kept most of their sitting bouts to less than 30 minutes had the lowest risk of death. The researchers felt that getting up and moving every half hour seems to protect against the health risks (cardiometabolic effects) from just sitting and sitting and sitting. Are you moving yet?

From Science Daily: Long sitting periods may be just as harmful as daily total

A new study finds that it isn't just the amount of time spent sitting, but also the way in which sitting time is accumulated during the day, that can affect risk of early deathThe study, published online today in Annals of Internal Medicine, found that adults who sit for one to two hours at a time without moving have a higher mortality rate than adults who accrue the same amount of sedentary time in shorter bouts.

The researchers used hip-mounted activity monitors to objectively measure inactivity during waking time over a period of seven days in 7,985 black and white adults over age 45. (The participants were taking part in the REGARDS study, a national investigation of racial and regional disparities in stroke.)

On average, sedentary behavior accounted for 77 percent of the participants' waking hours, equivalent to more than 12 hours per day. Over a median follow-up period of four years, 340 of the participants died. Mortality risk was calculated for those with various amounts of total sedentary time and various sedentary patterns. Those with the greatest amount of sedentary time -- more than 13 hours per day -- and who frequently had sedentary bouts of at least 60 to 90 consecutive minutes had a nearly two-fold increase in death risk compared with those who had the least total sedentary time and the shortest sedentary bouts.

The researchers also found that participants who kept most of their sitting bouts to less than 30 minutes had the lowest risk of death. "So if you have a job or lifestyle where you have to sit for prolonged periods of time, we suggest taking a movement break every half hour. This one behavior change could reduce your risk of death, although we don't yet know precisely how much activity is optimal," Dr. Diaz said. [Original study.]

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.

 Another reason exercise is good for you: A large study found that men who exercise after a diagnosis of prostate cancer (but which is not metastatic) had a lower risk of dying from prostate cancer - as compared to those men who don't exercise.

So get out there and do something that gets you moving - and yes, walking is an exercise (Note: 1 mile = 20 minutes of walking, thus 3 miles = 1 hour). In this study the average age at diagnosis was 71, but studies find that exercise has numerous benefits at all ages. Some doctors even think of exercise as "anticancer therapy" (here, here). Also, exercise has anti-inflammatory benefits, and current thinking is that chronic inflammation is linked to cancer.

The American Cancer Society in its cancer prevention guidelines recommends that adults should be physically active, and get at least 150 minutes of moderate physical activity or 75 minutes of vigorous intensity activity each week (or a combination of these), preferably spread throughout the week.

From Medscape: Exercise Linked to Lower Mortality With Early Prostate Cancer

Men with nonmetastatic prostate cancer may have longer survival the more they exercise, a recent study suggests. For these men, regular moderate or vigorous physical activity was associated with 31 percent to 37 percent lower likelihood of death during the study, compared to more modest amounts of exercise. “This confirms and expands on previous work that shows an inverse association between recreational physical activity after diagnosis and risk of prostate cancer-specific mortality,” said lead study author Ying Wang of the American Cancer Society in Atlanta, Georgia, in email to Reuters Health.

Wang and colleagues pulled data from a large, long-term study group established by the American Cancer Society in 1992, focusing on 7,000 men who were diagnosed with prostate cancer between 1992 and 2011. The average age at cancer diagnosis was 71, and there were 2,700 deaths through 2012, including 450 due to prostate cancer and 750 due to heart disease. The average time from diagnosis to death was about eight years for those who died from cancer and 10 years for those who died from other causes.

Men who were more active before diagnosis were more likely to have lower-risk cancer tumors and a history of prostate screenings. They were also leaner, more likely to be nonsmokers and vitamin users and they ate more fish. Both before and after diagnosis, walking accounted for 73 percent of the physical activity that men did, followed by 10 percent for cycling and 5 percent for aerobic exercise, according to the report online now in European Urology.

Based on exercise levels before diagnosis, moderate to vigorous exercise, including walking, was linked to lower risk of death from prostate cancer, but only for men with lower-risk tumors. But after the diagnosis, the same levels of exercise were linked to lower risk of death from prostate cancer for all men, although the apparent benefit of walking was no longer statistically meaningful. [Original study.]

 Guess what? Instead of babying our backs, we may have to be sure to get plenty of running, jogging, or brisk walking to make our backs stronger - specifically, to strengthen the discs in our spines. Once again, a study finds that exercise (here the upright exercise of running, jogging, or fast walking) has benefits. The authors of the study state that the research results go against conventional medical wisdom - that instead of weakening the spine (conventional view), those people who run or jog  many miles each week may actually be strengthening the discs of the spine. And maybe... the researchers suggest (though it needs to be verified first)... in the future, we may get medical prescriptions to jog or fast walk a certain number of miles each week to strengthen the discs in our spines.

The study found that the ideal speed for the spine health was a slow run or a fast walk (4 miles per hour). Specifically fast walking and slow running at about 2 meters per second (m/s) appeared the most beneficial. However, high impact exercises, or aerobic exercises, slower walking, or no exercise did not have these benefits.

Until now, discs had been considered a "slow tissue," thought to take much longer to respond to exercise than muscle. And that with age and use the discs degenerate, and nothing could really be done to improve them. But the study's findings suggest that exercise can benefit and strengthen the intervertebral disc (IVD) in the spine. As researcher Dr. Belavy said: "It's also important to reduce the amount of time spent in static postures, such as sitting or even standing still. Even going for a walk during a break at work, or choosing to take the stairs rather than the elevator is good for the discs, as well as for overall back health."

From NY Times: Why Running May Be Good for Your Back

People who regularly run or walk briskly appear to have healthier discs in their spines than people who do not exercise, according to one of the first studies to closely examine links between movement and disc health. The findings refute a widely held belief that activities like running might overtax the spine and indicate that, instead, they make it sturdierThe human spine is a complicated mechanism, composed of vertebral bones cushioned between intervertebral discs. These discs, shaped like tiny whoopee cushions, contain a viscous fluid that compresses and absorbs pressure during movement, keeping the back in good working form. With age, disease or injury, spinal discs can degenerate and bulge, resulting in back pain, which can be debilitating.

There were tantalizing hints in animal studies, however, that this idea could be out of date. ....So for the new study, which was published in April in Scientific Reports, researchers at Deakin University in Australia and other institutions decided to examine the backs of people who run and others who do not. Eventually they recruited 79 adult men and women, two-thirds of whom said that they were runners. Some of these told the researchers that they covered more than 30 miles (about 50 kilometers) a week in training. The researchers designated these as the “long-distance” group. The others said that they ran between 12 and 25 miles a week. All had been training for at least five years. The final group rarely exercised at all.

To ensure that people’s reported activity levels were accurate, the researchers asked their volunteers to wear accelerometers for a week. Then they scanned everyone’s spines, using a sophisticated type of M.R.I. that precisely measures the size and liquidity of each disc. And they found differences. In general, the runners’ discs were larger and contained more fluid than the discs of the men and women who did not exerciseSince both greater size and increased levels of internal fluid indicate better disc health, the runners harbored fundamentally healthier spines than the people who were sedentary, says Daniel Belavy, a professor of physical activity at Deakin University who led the study. Interestingly, mileage barely mattered

 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.

 An interesting study looked at what the act of walking does to our brain, and found that it can modify and increase the amount of blood that’s sent to the brain (which is viewed as beneficial for brain function). The study, performed by researchers at New Mexico Highlands University in the United States, found that the foot’s impact on the ground while walking sends pressure waves through the arteries, which can increase the blood supply to the brain. This is referred to as cerebral blood flow or CBF.

These results may help explain other studies that find those that walk frequently (about 6 to 9 miles per week) have "less cognitive impairment" or cognitive decline, fewer memory problems, and greater brain volume with aging.  Another good reason to get out and walk - good for the heart, the body, and the brain. From Science Daily:

How walking benefits the brain

You probably know that walking does your body good, but it's not just your heart and muscles that benefit. Researchers at New Mexico Highlands University (NMHU) found that the foot's impact during walking sends pressure waves through the arteries that significantly modify and can increase the supply of blood to the brain. The research will be presented today at the APS annual meeting at Experimental Biology 2017 in Chicago.

Until recently, the blood supply to the brain (cerebral blood flow or CBF) was thought to be involuntarily regulated by the body and relatively unaffected by changes in the blood pressure caused by exercise or exertion. The NMHU research team and others previously found that the foot's impact during running (4-5 G-forces) caused significant impact-related retrograde (backward-flowing) waves through the arteries that sync with the heart rate and stride rate to dynamically regulate blood circulation to the brain.

In the current study, the research team used non-invasive ultrasound to measure internal carotid artery blood velocity waves and arterial diameters to calculate hemispheric CBF to both sides of the brain of 12 healthy young adults during standing upright rest and steady walking (1 meter/second). The researchers found that though there is lighter foot impact associated with walking compared with running, walking still produces larger pressure waves in the body that significantly increase blood flow to the brain. While the effects of walking on CBF were less dramatic than those caused by running, they were greater than the effects seen during cycling, which involves no foot impact at all.

 A possible problem with running marathons is short term kidney injury in the two days right after the race. A study of 22 runners in the 2015 Hartford (Connecticut) Marathon found that most of the runners temporarily developed acute kidney injury (AKI) directly after the race. The study main author Chirag R. Parikh, MD, PhD said: "The kidney responds to the physical stress of marathon running as if it's injured, in a way that's similar to what happens in hospitalized patients when the kidney is affected by medical and surgical complications".

The runners studied fully recovered from the kidney injury 2 days after the event, but the study raises questions about the long-term effects for regular marathon runners, especially in warmer climates. Also, how about the effects of repeated marathons? The researchers say they can only speculate that marathoners adapt to the kidney injury, because they recover within 2 days. But they also pointed out that research has shown there are also changes in heart function associated with marathon running. Something else to keep in mind when considering training for marathons. From Science Daily:

Marathon running may cause short-term kidney injury

According to a new Yale-led study, the physical stress of running a marathon can cause short-term kidney injury. Although kidneys of the examined runners fully recovered within two days post-marathon, the study raises questions concerning potential long-term impacts of this strenuous activity at a time when marathons are increasing in popularity. More than a half million people participated in marathons in the United States in 2015.

While past research has shown that engaging in unusually vigorous activities -- such as mine work, harvesting sugarcane, and military training -- in warm climates can damage the kidneys, little is known about the effects of marathon running on kidney health. A team of researchers led by Professor of Medicine Chirag Parikh, M.D. studied a small group of participants in the 2015 Hartford Marathon. The team collected blood and urine samples before and after the 26.2-mile event. They analyzed a variety of markers of kidney injury, including serum creatinine levels, kidney cells on microscopy, and proteins in urine.

The researchers found that 82% of the runners that were studied showed Stage 1 Acute Kidney Injury (AKI) soon after the race. AKI is a condition in which the kidneys fail to filter waste from the blood. "The kidney responds to the physical stress of marathon running as if it's injured, in a way that's similar to what happens in hospitalized patients when the kidney is affected by medical and surgical complications," said Parikh. The researchers stated that potential causes of the marathon-related kidney damage could be the sustained rise in core body temperature, dehydration, or decreased blood flow to the kidneys that occur during a marathon. [Original study.]