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Published on Leave a comment on Being Overweight In Midlife and Higher Risk of Dementia

Interesting study results - being overweight (a higher body mass index or BMI) is linked to dementia more than 20 years later, but in the few years before dementia onset body mass index (BMI) is lower in those who develop dementia than in those who don't develop dementia. The researchers hypothesize that 2 processes are going on:  A higher BMI (overweight or obese) in mid-life is harmful (a direct effect), and then there is weight loss during the preclinical dementia phase. Bottom line: best is a normal weight in mid-life to try to prevent dementia later on in life. From Science Daily:

Obesity increases dementia risk

People who have a high body mass index (BMI) are more likely to develop dementia than those with a normal weight, according to a new UCL-led study. The study, published in the Alzheimer's & Dementia journal, analysed data from 1.3 million adults living in the United States and Europe. The researchers also found that people near dementia onset, who then go on to develop dementia, tend to have lower body weight than their dementia-free counterparts.

"The BMI-dementia association observed in longitudinal population studies, such as ours, is actually attributable to two processes," said lead author of the study, Professor Mika Kivimäki (UCL Institute of Epidemiology & Health). "One is an adverse effect of excess body fat on dementia risk. The other is weight loss due to pre-clinical dementia. For this reason, people who develop dementia may have a higher-than-average body mass index some 20 years before dementia onset, but close to overt dementia have a lower BMI than those who remain healthy."

In this study, researchers from across Europe pooled individual-level data from 39 longitudinal population studies from the United States, the United Kingdom, France, Sweden, and Finland. A total of 1,349,857 dementia-free adults participated in these studies and their weight and height were assessed. Dementia was ascertained using linkage to electronic health records obtained from hospitalisation, prescribed medication and death registries.

A total of 6,894 participants developed dementia during up to 38 years of follow-up. Two decades before symptomatic dementia, higher BMI predicted dementia occurrence: each 5-unit increase in BMI was associated with a 16-33% higher risk of this condition (5 BMI units is 14.5 kg for a person 5'7" (170 cm) tall, approximately the difference in weight between the overweight and normal weight categories or between the obese and overweight categories). In contrast, the mean level of BMI during pre-clinical stage close to dementia onset was lower compared to that in participants who remained healthy. [Original study.]

Published on Leave a comment on Coffee Linked to a Number of Health Benefits

Great news coffee drinkers! Another study - this time a large analysis of over 200 studies found that coffee consumption is linked to many health benefits. The best results were from drinking 3 to 4 cups of coffee daily (as compared to none), with a reduction in "all cause" mortality (death from any cause), and cardiovascular disease and death.

They also found a lower risk of cancer in general, and with a lower risk of several specific cancers (endometrial, prostate, melanoma, non-melanoma skin cancer, liver cancer) and neurological (Parkinson's disease, Alzheimer's disease, and depression), metabolic (including type 2 diabetes, metabolic syndrome), and liver conditions.

However, during pregnancy high coffee consumption (as compared to low or no consumption) was associated with low birth weight, preterm birth in the first and second trimester, and pregnancy loss. The researchers also found an association between coffee drinking and a small risk of fracture in women, but not in men. Decaffeinated coffee seemed to have many of the same benefits as caffeinated coffee - especially at 2 to 4 cups a day.

[UPDATE: A 2020 review of studies found that ingesting caffeine during pregnancy is linked to health problems and that there is no safe level during pregnancy. In other words,  caffeine and caffeinated beverages should be avoided during pregnancy and when trying to conceive.]

Excerpts from Science Daily:

Three to four cups of coffee a day linked to longer life

Drinking coffee is "more likely to benefit health than to harm it" for a range of health outcomes, say researchers in The BMJ today. They bring together evidence from over 200 studies and find that drinking three to four cups of coffee a day is associated with a lower risk of death and getting heart disease compared with drinking no coffee. Coffee drinking is also associated with lower risk of some cancers, diabetes, liver disease and dementia. However, they say drinking coffee in pregnancy may be associated with harms, and may be linked to a very small increased risk of fracture in women.

The included studies used mainly observational data, providing lower quality evidence, so no firm conclusions can be drawn about cause and effect, but their findings back up other recent reviews and studies of coffee intake. As such, they say, excluding pregnancy and women at risk of fracture, "coffee drinking appears safe within usual patterns of consumption" and they suggest that coffee could be safely tested in randomised trials.

To better understand the effects of coffee consumption on health, a team led by Dr Robin Poole, Specialist Registrar in Public Health at the University of Southampton, with collaborators from the University of Edinburgh, carried out an umbrella review of 201 studies that had aggregated data from observational research and 17 studies that had aggregated data from clinical trials across all countries and all settings. (Original study.)

Published on Leave a comment on Spanking Children Doesn’t Work

Another large study found problems with parents spanking children - specifically that spanking may make a child's behavior worse over time. More than 50 countries ban spanking, but many parents still spank in the US (and yes, it is legal). Unfortunately some states in the US also allow spanking (corporal punishment) in schools even today, which is viewed by many as physical abuse.

Psychologists at the University of Texas at Austin and the University of Virginia found that children who were spanked by their parents at age five years were more likely to have behavioral problems between the ages 6 and 8. "Our findings suggest that spanking is not an effective technique and actually makes children's behavior worse not better," says lead author Elizabeth T Gershoff.

The researchers had 2 main conclusions. First:They found no evidence that spankings in general or recent spankings are effective at reducing "externalizing behavior problems" (e.g., fighting, arguing, getting angry, disrupting activities, being impulsive - as reported by their teachers) over time.  Instead, this study (like others) found that instead spanking children predicts more behavior problems in the future in children. And secondly, while the number of spankings was important (frequent vs not frequent spankings) with the result that children receiving frequent spankings had more behavior problems later, they also found  that a child who is spanked even once is more likely to have behavior problems in the future than a similar child who is never spanked. From Medical Xpress:

Spanking linked to increase in children's behavior problems

Children who have been spanked by their parents by age 5 show an increase in behavior problems at age 6 and age 8 relative to children who have never been spanked, according to new findings in Psychological Science, a journal of the Association for Psychological Science. The study, which uses a statistical technique to approximate random assignment, indicates that this increase in behavior problems cannot be attributed to various characteristics of the child, the parents, or the home environment - rather, it seems to be the specific result of spanking.

Gershoff and coauthors Kierra M. P. Sattler (University of Texas at Austin) and Arya Ansari (University of Virginia) examined data from 12,112 children who participated in the nationally representative Early Childhood Longitudinal Study. When the children were 5 years old, their parents reported how many times they had spanked their child in the past week (if any). The researchers classified any child whose parent provided a number other than zero as having been spanked.

The researchers then matched children who had been spanked with those who hadn't according to 38 child- and family-related characteristics, including: the child's age, gender, overall health, and behavior problems at age 5; the parent's education, age... Pairing the children in this way yielded two groups of children whose main difference was whether their parents had spanked them, effectively accounting for other factors that could plausibly influence the behavior of both parent and child. This approach allowed the researchers to approximate the random assignment of participants to groups, a hallmark of experimental design.

To gauge children's behavior problems over time, Gershoff, Sattler, and Ansari examined teachers' ratings when the children were 5, 6, and 8 years old. Children's teachers reported the frequency with which the children argued, fought, got angry, acted impulsively, and disturbed ongoing activities. The results were clear: Children who had been spanked at age 5 showed greater increases in behavior problems by age 6 and also by age 8 when compared with children who had never been spanked.

Gershoff and colleagues conducted a similar analysis with only those children who had been spanked by their parents, comparing children who had been spanked in the week before the study (which suggests frequent spanking) and those who had not. Children spanked in the past week at age 5 also experienced greater increases in problem behavior at age 6 and 8 compared with children not spanked as frequently.

Published on Leave a comment on Vitamin D Supplements During Pregnancy?

Vitamin D supplements are incredibly popular, but whether vitamin D supplements should be taken during pregnancy and at what dose is still debated, and studies have had conflicting results. Now a review by Canadian researchers of 43 studies of vitamin D supplementation during pregnancy found that there is "insufficient evidence to guide recommendations during pregnancy". They said that overall the studies were small or of low quality -  and the "available data did not provide evidence of benefit" from vitamin D supplementation during pregnancy.

They found that vitamin D supplementation slightly increased the mean (average) birth weight by 2 ounces (58.33 g), reduced the risk of small for gestational age births, and reduced the risk of the child wheezing at age 3. There was no effect on preterm birth, and there was a lack of evidence of benefits of prenatal vitamin D supplementation for maternal health conditions (e.g. gestational diabetes) during pregnancy.

Currently recommendations regarding vitamin D supplementation vary widely among medical and professional organizations, and WHO (World Health Organization) currently recommends against routine prenatal vitamin D supplementation. Luckily there are a number of studies going on right now on this issue that may help answer this question - how much vitamin D, if any, should be taken during pregnancy? From Medical Xpress:

Insufficient evidence to guide recommendations on vitamin D in pregnancy

There is currently insufficient evidence to guide recommendations on the use of vitamin D supplements in pregnancy, conclude researchers in The BMJ today. A team led by Dr Daniel Roth at The Hospital for Sick Children in Toronto, say some of the most critical questions about the effectiveness of taking vitamin D supplements during pregnancy "will probably remain unanswered in the foreseeable future."

Vitamin D helps maintain calcium levels in the body to keep bones, teeth and muscles healthy. Numerous studies suggest that taking vitamin D supplements may also help protect against heart disease, cancer, respiratory infections and asthma - as well as conditions related to pregnancy, such as preeclampsia and gestational diabetes. But results are conflicting and recommendations vary widely among medical and professional organisations.

So Dr Roth and his team set out to assess the current and future state of the evidence on vitamin D supplements during pregnancy. They analysed results from 43 randomised controlled trials involving 8,406 women, to estimate the effects of taking vitamin D supplements during pregnancy on 11 maternal and 27 child outcomes.... The results show that taking supplements during pregnancy increased vitamin D levels in both the mother's bloodstream and umbilical cord blood, but the researchers did not consistently find that higher doses of vitamin D led to healthier women and babies.

Overall, vitamin D increased average birth weight by 58 g and reduced the risk of having a small baby, but more detailed analyses weakened the authors' confidence in these findings. There was a lack of evidence of benefits of vitamin D supplements for maternal health conditions related to pregnancy, no effect on other birth outcomes of public health importance, such as premature birth, and scant evidence on safety outcomes.  [Original study.]

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Published on 1 Comment on Health Benefits of Dog Ownership

There are health benefits to having a dog, based on results from studies and testimonials from dog owners. Now a study of millions of Swedes found  that dog ownership is associated with a lower risk of cardiovascular disease (CVD) in single-person households and a lower risk of death from cardiovascular or other causes ("all cause mortality") in general. Owning a hunting dog breed had the strongest association with cardiovascular health. Some of these health benefits are due to dogs providing companionship, affection, and increased physical activity (all those walks) of their owners. And of course there's sharing of microbes. From Science Daily:

Dog ownership linked to lower mortality rate

A team of Swedish scientists have used national registries of more than 3.4 million Swedes aged 40 to 80 to study the association between dog ownership and cardiovascular health. Their study shows that dog owners had a lower risk of death due to cardiovascular disease or to other causes during the 12-year follow-up. A total of more than 3.4 million individuals without any prior cardiovascular disease in 2001 were included in the researchers' study linking together seven different national data sources, including two dog ownership registers. 

"A very interesting finding in our study was that dog ownership was especially prominent as a protective factor in persons living alone, which is a group reported previously to be at higher risk of cardiovascular disease and death than those living in a multi-person household. Perhaps a dog may stand in as an important family member in the single households. The results showed that single dog owners had a 33 percent reduction in risk of death and 11 percent reduction in risk of cardiovascular disease during follow-up compared to single non-owners. Another interesting finding was that owners to dogs from breed groups originally bred for hunting were most protected," says Mwenya Mubanga, lead junior author of the study and PhD student at the Department of Medical Sciences and the Science for Life Laboratory, Uppsala University.

"These kind of epidemiological studies look for associations in large populations but do not provide answers on whether and how dogs could protect from cardiovascular disease. We know that dog owners in general have a higher level of physical activity, which could be one explanation to the observed results. Other explanations include an increased well-being and social contacts or effects of the dog on the bacterial microbiome in the owner," says Tove Fall, senior author of the study and Associate Professor in Epidemiology at the Department of Medical Sciences and the Science for Life Laboratory, Uppsala University. "There might also be differences between owners and non-owners already before buying a dog, which could have influenced our results, such as those people choosing to get a dog tending to be more active and of better health." [Original study.]

Published on Leave a comment on Air Pollution Has an Effect On Sperm?

Air pollution is linked to so many negative health effects, now another one - poorer quality sperm. In this study 6475 males  (ages ranged from 15–49 years) had their sperm analyzed as part of a standard medical examination program in Taiwan. They were also able to get air pollution measurements for each person's address for that time period. They found that both short-term and long-term exposure to higher levels of fine particulate matter (PM2.5) pollution were linked to lower numbers of sperm being normal in size and shape (sperm morphology), but with a higher concentration of sperm. Perhaps a  compensatory phenomenon?

The researchers pointed out that other studies have also found effects from air pollution on sperm. Since this study only analyzed a person's sperm one time, the findings are correlational (they observed an association, but couldn't definitely say it caused the effect). [Some other posts on sperm quality: here, here, here.] From Medical Xpress:

Air pollution linked to poorer quality sperm

Air pollution, particularly levels of fine particulate matter (PM2.5), is associated with poorer quality sperm, suggests research published online in Occupational & Environmental Medicine. Although the size of the effect is relatively small in clinical terms, given how widespread air pollution is, this might spell infertility for a "significant number of couples," say the researchers.

Environmental exposure to chemicals is thought to be a potential factor in worsening sperm quality, but the jury is still out on whether air pollution might also have a role. To explore this possibility further, the international team of researchers looked at the impact on health of short and long term exposure to fine particulate matter (PM2.5) among nearly 6500 15 to 49 year old men in Taiwan.

The men were all taking part in a standard medical examination programme between 2001 and 2014, during which their sperm quality was assessed (total numbers, shape/size, movement) as set out by World Health Organization guidelines. PM2.5 levels were estimated for each man's home address for a period of three months, as that is how long it takes for sperm to be generated, and for an average of 2 years, using a new mathematical approach combined with NASA satellite data.

A strong association between PM2.5 exposure and abnormal sperm shape was found. Every 5 ug/m3 increase in fine particulate matter across the 2 year average was associated with a significant drop in normal sperm shape/size of 1.29 per cent. And it was associated with a 26 per cent heightened risk of being in the bottom 10 per cent of normal sperm size and shape, after taking account of potentially influential factors, such as smoking and drinking, age or overweight. However, it was also associated with a significant increase in sperm numbers, possibly as a compensatory mechanism to combat the detrimental effects on shape and size, suggest the researchers. Similar findings were evident after three months of exposure to PM2.5. [Original study.]

Published on Leave a comment on Disinfectant Use By Nurses Linked to COPD

There are a number of professions where there is an elevated risk for getting chronic obstructive pulmonary disease (COPD) from all the vapors, gases, dust, fumes, and chemicals (all irritants) that one inhales - such as welders, coal miners, cotton textile workers, construction, farmers, even hairdressers. Now a study suggests that nurses who use disinfectants at least once a week are also at higher risk for COPD. The specific disinfectants associated with COPD are glutaraldehyde, bleach, hydrogen peroxide, alcohol, and quats (quaternary ammonium compounds).

From Medscape: Exposure to Disinfectants Linked to COPD

The risk for chronic obstructive pulmonary disease (COPD) is higher in those who use disinfectants at least once a week than in those who do not, a preliminary observational study of a large cohort of female nurses in the United States reveals. 

For their study, Dr Dumas and her colleagues analyzed data from the Nurses' Health Study II. From 2009 to 2017, participants completed a survey every 2 years. ..... And they used the job-task exposure matrix to evaluate seven major disinfectants: formaldehyde, glutaraldehyde, hypochlorite bleach, hydrogen peroxide, alcohol, quaternary ammonium compounds (or quats), and enzymatic cleaners.

In the cohort of 55,185 women who were nursing in 2009, 663 reported incident physician-diagnosed COPD during the follow-up period. The team found an association between incident COPD and high-level exposure to glutaraldehyde, bleach, hydrogen peroxide, alcohol, and quats. Of the nurses diagnosed with COPD, 37% reported the weekly use of disinfectants to clean surfaces, and 19% reported weekly use to clean instruments. Regression models demonstrated that the risk for COPD was 22% higher for nurses who cleaned instruments, and 32% higher for nurses who cleaned surfaces.

We've been aware of the association between disinfectants and asthma for some time, she told Medscape Medical News.... There's no easy solution, Dr Dumas acknowledged. "Protection from infection is important, but so is the health of workers." Green products might be one solution, "but we're not sure of their effect on health either. Just because they're natural, doesn't mean they're safe; they can have allergens." Another solution could be ultraviolet light, as previously reported by Medscape Medical News.

This was a "well-performed study," said Lidwien Smit, PhD, from the University of Utrecht in the Netherlands. "I just wonder about the pathology, and how it influences the microbiome. Disinfectants are meant to kill off bacteria, but if you're exposed to large concentrations, you're also inhaling them, which could affect your airway microbes," she explained. In fact, disinfectants could play a role in killing off bacterial communities in the airways that are responsible for "immune homeostasis" and keep users healthy, she added. If that immune balance gets disturbed, it might have an influence on a person's reaction to pathogens or inflammation. 
Chest X-ray of person with COPD. Credit: Wikipedia

Published on Leave a comment on Could A Vitamin Supplement Help Those With Asthma?

An interesting possibility - that taking supplements of  a type of vitamin E known as gamma tocopherol may reduce the inflammation of the airways common in asthma patients – eosinophilic inflammation.

Note that these findings were from a preliminary study of 15 people with mild asthma, done by researchers at the Univ. of North Carolina. Now larger and longer studies need to be done, especially to make sure that side-effects and an increased risk for hemorrhagic stroke won't occur with gamma tocopherol, as it does for the other form of vitamin E (alpha tocopherol) commonly found in supplements. From Medical Xpress:

Can asthma be controlled with a vitamin supplement?

The shortness of breath experienced by the nearly 26 million Americans who suffer from asthma is usually the result of inflammation of the airways. People with asthma typically use albuterol for acute attacks and inhaled steroids to limit chronic inflammation. Both medications come with side effects. But what if it was possible to keep asthma under control by changing one's diet or taking a vitamin supplement? It may happen sooner than you think.

Preliminary research results from the UNC School of Medicine indicate that a type of vitamin E known as gamma tocopherol may reduce eosinophilic inflammation – a kind of airway inflammation common in asthma patients. The results were published in the Journal of Allergy & Clinical Immunology.

"We started looking into vitamin E because epidemiologic data suggested that people with high amounts of vitamin E in their diet were less prone to asthma and allergic disease," said Michelle Hernandez, MD, professor of pediatrics and senior author of the study.  There are several different isoforms of vitamin E. The type commonly found in vitamin supplements – alpha tocopherol – has been studied previously, but the results suggested that alpha tocopherol was not particularly effective. Even worse, the alpha isoform seemed to be associated with an increased risk for hemorrhagic stroke.

So UNC researchers took a different tack and asked whether the kind of vitamin E being used might have an effect on the outcome. They began looking more closely at gamma tocopherol, the type of vitamin E commonly found in a diet rich in nuts and nut oil. .... "While the alpha isoform does have antioxidant activities, gamma tocopherol has both an antioxidant and a very unique anti-inflammatory action as well," she said "That anti-inflammatory effect is what we think made the difference in this study."

Participants in the study were randomized into two groups that received either gamma tocopherol supplement or a placebo for two weeks. At the end of that period, they were asked to cough up sputum..... After a three week "washout period" where they took nothing, subjects were placed in the other group: if they took the supplement for the first two weeks, they took a placebo for the second period.

"The advantage of a cross-over design like this is that we are able to compare the subjects to themselves," said Burbank. "And what we found is that when people were taking the vitamin E supplement, they had less eosinophilic inflammation." In addition to decreased inflammation, those who were taking vitamin E were also found to have lower levels of proteins called mucins, which affect the stickiness of mucus. Mucins are often elevated in asthmatics.

Published on Leave a comment on Gum Disease Linked To Several Cancers

A large study by researchers at the State University of NY, of 65,869 postmenopausal women found that those who have a history  of gum or periodontal disease also have an overall higher risk of cancer. The women with a history of periodontal disease also had an increased risk for several specific cancers: breast, esophageal, gallbladder, lung and melanoma cancers. This cancer and gum disease association occurred in both nonsmokers and smokers.

How is periodontal disease "promoting" cancer? How it occurs is still unclear, but one theory suggests the gum disease bacteria are in the saliva, which is swallowed, and so the bacteria get into the gut, esophagus, or lungs. Or bacteria from diseased gum tissues get into "systemic circulation" and so get to distant sites in the body.  One of the researchers pointed out that "Certain periodontal bacteria have been shown to promote inflammation even in tiny amounts, and these bacteria have been isolated from many organ systems and some cancers including esophageal cancers."

From Medscape: Gum Disease and Increased Link to Many Cancers

Brushing, flossing, and regular dental checkups appear to do much more than maintain a healthy smile. Now, a large prospective cohort study shows that postmenopausal women with a history of periodontal disease, including those who have never smoked, are at significantly increased overall risk for cancer as well as site-specific cancers, including lung, breast, esophageal, gallbladder, and melanoma skin cancers.

The study authors note that these results add to the growing body of evidence from smaller studies and studies in men that link periodontal disease to total cancer risk. The Centers for Disease Control and Prevention (CDC) estimate that 47% of adults 30 years of age and older in the United States have some form of periodontal disease, ranging from mild to severe. At age 65 years and older, however, 70% of adults have moderate to severe periodontal disease, according to the CDC.

The study involved almost 66,000 postmenopausal women in the United States, who were enrolled in the ongoing Women's Health Initiative Observational Study (WHI-OS). During a mean follow-up of 8.32 years, the team identified 7149 cancers and found that periodontal disease history was associated with a 14% increased total cancer risk. When analyses were limited to 34,097 never-smokers, there was also an increased risk for overall cancer.

An association between periodontal disease and site-specific cancers was observed in breast, lung, esophageal, gallbladder, and melanoma skin cancers. There was a borderline association with stomach cancer, the study authors report, and periodontal disease was not associated with cancers of the pancreas; liver; lower digestive tract organs; or lip, oral cavity, and pharynx combined. Similarly, there was no association with genitourinary and lymphoid and hematopoietic malignancies.

For the study, the investigators looked at periodontal disease information in 65,869 women aged 54 to 86 years at 40 US centers. Mean age was 68 years. Most women were non-Hispanic whites with some college education. All participants answered the question "Has a dentist or dental hygienist ever told you that you had periodontal or gum disease? (No/Yes)" between 1999 and 2003 on the annual Year-5 WHI-OS follow-up questionnaire. Cancer outcomes were documented through September 2013 with a maximum 15-year follow-up period.

 Women who reported a history of periodontal disease were also more likely to report a history of smoking, secondhand smoke exposure, alcohol use, hormone therapy (estrogen plus progestin), and a cancer diagnosis, the study authors report. At the same time, no significant differences were observed in body mass index, physical activity levels, or history of diabetes between women with periodontal disease and those without. [Original study.]

Published on Leave a comment on Exercise Is a Maintenance Program For the Brain?

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.