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There are health benefits to babies from being breastfed, including that breast milk contains hundreds of microbial species which are transmitted to the baby. There are also health benefits to the mother, including a lower risk of breast cancer and ovarian cancer. In addition, a multicenter study in the United States found that breastfeeding lowers the mother's risk of type 2 diabetes over the next 30 years - by up to 47%.

In general: the study found that the longer a woman breastfeeds, the lower her risk of developing type 2 diabetes. Thus one can say that breastfeeding has a "protective" effect for type 2 diabetes. From Medical Xpress:

Thirty-year study shows women who breastfeed for six months or more reduce their diabetes risk

In a long-term national study, breastfeeding for six months or longer cuts the risk of developing type 2 diabetes nearly in half for women throughout their childbearing years, according to new Kaiser Permanente research published Jan. 16 in JAMA Internal Medicine. "We found a very strong association between breastfeeding duration and lower risk of developing diabetes, even after accounting for all possible confounding risk factors," said lead author Erica P. Gunderson, PhD, MS, MPH, senior research scientist with the Kaiser Permanente Division of Research.

Women who breastfed for six months or more across all births had a 47 percent reduction in their risk of developing type 2 diabetes compared to those who did not breastfeed at all. Women who breastfed for six months or less had a 25 percent reduction in diabetes risk.

Dr. Gunderson and colleagues analyzed data during the 30 years of follow up from the Coronary Artery Risk Development in Young Adults (CARDIA) study, a national, multi-center investigation of cardiovascular disease risk factors that originally enrolled about 5,000 adults aged 18 to 30 in 1985 to 1986, including more than 1,000 members of Kaiser Permanente Northern California.The new findings add to a growing body of evidence that breastfeeding has protective effects for both mothers and their offspring, including lowering a mother's risk of breast and ovarian cancer.

The long-term benefits of breastfeeding on lower diabetes risk were similar for black women and white women, and women with and without gestational diabetes. Black women were three times as likely as white women to develop diabetes within the 30-year study, which is consistent with higher risk found by others. Black women enrolled in CARDIA were also less likely to breastfeed than white women.

"The incidence of diabetes decreased in a graded manner as breastfeeding duration increased, regardless of race, gestational diabetes, lifestyle behaviors, body size, and other metabolic risk factors measured before pregnancy, implying the possibility that the underlying mechanism may be biological," Gunderson said. Several plausible biological mechanisms are possible for the protective effects of breastfeeding, including the influence of lactation-associated hormones on the pancreatic cells that control blood insulin levels and thereby impact blood sugar.

This study included 1,238 black and white women who did not have diabetes when they enrolled in CARDIA, or prior to their subsequent pregnancies. Over the next 30 years, each woman had at least one live birth and was routinely screened for diabetes under the CARDIA protocol, which included diagnostic screening criteria for diabetes. Participants also reported lifestyle behaviors (such as diet and physical activity) and the total amount of time they breastfed their children.

 Breastfeeding a baby. Credit: Wikipedia Commons, Anton Nossik.

A recent study by a team of researchers from France and Denmark highlighted the point that all medicines have side-effects, even though we may not realize it for years. Ibuprofen is a great non-prescription pain reliever - a nonsteroidal anti-inflammatory drug (NSAID), but it should be taken only when needed. Ibuprofen is found in such commonly used medicines as Advil and Motrin. The researchers found that ibuprofen has antiandrogenic effects (alters or disrupts the endocrine system) which results in a temporary condition called "compensated hypogonadism" when taken for extended periods by healthy young men (in the study 600 mg was taken daily for 6 weeks).

The researchers stress that this "depression of important aspects of testicular function, including testosterone production" was temporary from short term use, but they were concerned with those who take it daily for longer periods, such as athletes. They wondered whether this could be contributing to lowered sperm levels and the drops in male fertility that we are seeing in western developed countries. [Note that ibuprofen use has also been linked to a higher risk of cardiac arrest.] From Medical Xpress:

Taking ibuprofen for long periods found to alter human testicular physiology

A team of researchers from Denmark and France has found that taking regular doses of the pain reliever ibuprofen over a long period of time can lead to a disorder in men called compensated hypogonadism. In their paper published in Proceedings of the National Academy of Sciences, the group describes their study, which involved giving the drug to volunteers and monitoring their hormones and sperm production.

To learn more about the possible impacts of the popular anti-inflammation drug Ibuprofen on male fertility when taken for long periods of time, the researchers asked 31 men between the ages of 18 and 35 to take 600 milligrams (three tablets) a day of the drug for six weeks. Other volunteers were given a placebo. Over the course of the study, the volunteers were tested to see what impact the drug had on their bodies.

The researchers report that just two weeks into the study, they found that all of the volunteers had an increase in luteinizing hormones, which the male body uses to regulate the production of testosterone. The increase indicated that the drug was causing problems in certain cells in the testicles, preventing them from producing testosterone, which is, of course, needed to produce sperm cells. They further report that the change caused the pituitary gland to respond by producing more of another hormone, which forced the body to produce more testosterone. The net result was that overall testosterone levels remained constant, but the body was overstressing to compensate for the detrimental impact of the Ibuprofen—a state called compensated hypogonadism.

The researchers note that while compensated hypogonadism can cause a temporary reduction in the production of sperm cells, reducing fertility, it is generally not cause for alarm. What is more of a concern, they note, is using the drug for longer periods of time. It has not been proven yet, but the researchers suspect such use, as is seen with some professional athletes or others with chronic pain issues, might lead to a condition called overt primary hypogonadism, in which the symptoms become worse—sufferers report a reduction in libido, muscle mass and changes in mood. Additional studies are required, they note, to find out if this is, indeed, the case. [Original study.]

A recent study's results give hope to those who haven't really exercised or been physically active as they've gone through middle-age (it's viewed as "sedentary aging") and wonder if this dooms them in some way. Is it too late to get benefits from starting to exercise now? Studies show that being sedentary (that is, not being physically active or exercising weekly) and in "poor physical fitness" in middle-age is a risk factor for later heart failure. This is because a consequence of "sedentary aging" is stiffness of the heart, specifically the left ventricle (thus a loss of "cardiac plasticity").

But the study found that after 2 years of an exercise program in (formerly) sedentary middle-aged adults, they improved their maximal oxygen uptake, decreased the heart's stiffness, and improved overall fitness. All good. So the bottom line is: No, it's not too late to start exercising. The heart has elasticity and can remodel itself if the exercise is started before age 65 and is done 4 to 5 times a week. The adults studied were both male and female, between the ages of 45 and 64,  and exercised or were physically active for a total of 150 to 180 minutes a week, which meant at least 30 minutes 4 or 5 times a week.

Looking at the study's exercise regimen, it's clear that a variety of exercises or physical activities (low, moderate, and high intensity) is necessary. Some of the time one should be active or exercise to a point of breaking a sweat and feeling the heart pump. This meant that over time the participants increased their exercise frequency, duration, and intensity. Think about it - as you get more fit, it takes more to get your heart pumping and to break a sweat, and you can handle more exercise. 

Unfortunately the "control group", who did a combination of yoga, balance, and strength training 3 times a week for 2 years did not show improvements in heart plasticity, maximal oxygen uptake, or in overall fitness.Yikes. Sooo...the study clearly shows it is worth getting off your butt and making the effort to exercise. Perhaps view it as brushing your teeth - a daily nuisance, but necessary for health. The researchers themselves stated "Exercise is medicine." From Science Daily:

Proper exercise can reverse damage from heart aging

Exercise can reverse damage to sedentary, aging hearts and help prevent risk of future heart failure -- if it's enough exercise, and if it's begun in time, according to a new study by cardiologists at UT Southwestern and Texas Health Resources. To reap the most benefit, the exercise regimen should begin by late middle age (before age 65), when the heart apparently retains some plasticity and ability to remodel itself, according to the findings by researchers at the Institute for Exercise and Environmental Medicine (IEEM), which is a collaboration between UT Southwestern Medical Center and Texas Health Presbyterian Hospital Dallas.

And the exercise needs to be performed four to five times a week. Two to three times a week was not enough, the researchers found in an earlier study..... The regimen included exercising four to five times a week, generally in 30-minute sessions, plus warmup and cool-down: One of the weekly sessions included a high-intensity 30-minute workout, such as aerobic interval sessions in which heart rate tops 95 percent of peak rate for 4 minutes, with 3 minutes of recovery, repeated four times (a so-called "4 x 4"). Each interval session was followed by a recovery session performed at relatively low intensity. One day's session lasted an hour and was of moderate intensity. (As a "prescription for life," Levine said this longer session could be a fun activity such as tennis, aerobic dancing, walking, or biking.) One or two other sessions were performed each week at a moderate intensity, meaning the participant would break a sweat, be a little short of breath, but still be able to carry on a conversation -- the "talk test.".... One or two weekly strength training sessions using weights or exercise machines were included on a separate day, or after an endurance session.

The more than 50 participants in the study were divided into two groups, one of which received two years of supervised exercise training and the other group, a control group, which participated in yoga and balance training.A t the end of the two-year study, those who had exercised showed an 18 percent improvement in their maximum oxygen intake during exercise and a more than 25 percent improvement in compliance, or elasticity, of the left ventricular muscle of the heart, Dr. Levine noted. He compared the change in the heart to a stretchy, new rubber band versus one that has gotten stiff sitting in a drawer. Sedentary aging can lead to a stiffening of the muscle in the heart's left ventricle, the chamber that pumps oxygen-rich blood back out to the body, he explained.

"When the muscle stiffens, you get high pressure and the heart chamber doesn't fill as well with blood. In its most severe form, blood can back up into the lungs. That's when heart failure develops," said Dr. Levine, who holds the S. Finley Ewing Chair for Wellness at Texas Health Dallas and the Harry S. Moss Heart Chair for Cardiovascular Research. Earlier research by UT Southwestern cardiologists showed that left ventricular stiffening often shows up in middle age in people who don't exercise and aren't fit, leaving them with small, stiff chambers that can't pump blood as well[Original study.]

I recently read a nice article discussing indoor air pollution, which can be worse than outdoor air, even that of cities. Yes, that's true! In past posts I've discussed problems (and health issues) with air fresheners, fragrances, incensedryer sheets, scented candles, synthetic rugs, "stain-proofing", and flame retardants in upholstery, but this article is about furniture and how it can emit various chemicals ("outgassing"), especially when new. Think of all the stains, glues, paints, etc. used in making furniture.

The article points out that when buying new furniture, can look to see if it is certified by Greenguard or SCS Global Services as having low or no emissions of  hazardous chemicals. Another thing to do is avoid particle boardengineered wood, or pressed wood (frequently emits formaldehyde, a carcinogen). But in the mean time - it's generally a good idea to frequently get fresh air in your residence by opening windows for a while. Excerpt's from E. Leamy's article in the Washington Post:

Your furnishings could be causing indoor air pollution

We feel safe in our homes, but that can be a false sense of security. The threat I’m talking about is something we can’t see: indoor air pollution. The air in our homes and workplaces can be more polluted than outdoor air in the most industrialized citiesaccording to the Environmental Protection Agency. The EPA says the problem is compounded by the fact that Americans spend 90 percent of their time indoors. Many different things can cause indoor air pollution, and they have a cumulative effect on our health.

Let’s look at one of those possible sources: our furnishings. Yes, your new carpet or cabinet could be subtly poisoning you with chemicals such as benzene, ethylene glycol or formaldehyde. It’s called “off-gassing.” Four of the top 10 chemicals emitted from furnishings are considered “acute” hazards, or irritants. “Poor indoor air quality can cause or contribute to the development of infections, lung cancer and chronic lung diseases such as asthma,” according to the American Lung Association.

How do researchers know that some furnishings emit harmful gaseous chemicals? Greenguard, a division of UL Environment, has developed a way of testing furniture to find out. In a ­generic-looking office park outside Atlanta, researchers heft furniture into giant, airtight chambers. .... Greenguard developed the testing method so manufacturers who wanted to sell low-emission furniture could prove their products were healthier. UL awards its Greenguard certification to furniture that emits low or no levels of hazardous chemicals

Manufacturers don’t have to state what chemicals they use in their furnishings. The EPA singles out engineered wood — otherwise known as particleboard — as being particularly prone to emitting formaldehyde, a probable carcinogen. UL Environment adds that products that are applied wet, such as glues and paints, often off-gas while they are curing. Sometimes a strong industrial odor is a good hint that a piece of furniture is emitting chemicals. If you develop a headache while inside a building where paints, stains or glues are being used, that’s another clue. 

However, it is possible to know whether harmful chemicals are not present, because more and more furnishings are being certified as having low emissions. Here are certifications you can look for and other steps you can take to reduce your exposure to indoor air pollution from your furnishings: 

1. Check certifications. Look for an indoor-air-quality certification, such as the one offered by Greenguard. Another firm that certifies low-emission furniture is SCS Global Services2. Air out. .... 3. Paint first. If you’re renovating your house, paint it and air it out before installing carpeting and curtains, because they can absorb chemical fumes from the paint..... 4. Buy used. Off-gassing diminishes over time, so buying older furniture can be better. ....5. Avoid particleboard. This material is also called pressed wood, engineered wood and MDF. The glues used to hold the material together often contain harmful chemicals such as formaldehyde. Alternatively, look for certified particleboard products. 6. Choose unscented. .... 7. Beyond furnishings. Other products frequently used in homes can also off-gas and cause indoor air pollution. 

For those who need convincing that lifestyle can contribute to development of cancer or its prevention, new medical research has once again supported the importance of lifestyle choices. A report from Australian researchers (with similar findings as a study in the US) stated: an estimated 38% of cancer deaths and 33% of cancer diagnoses could have been prevented with healthy lifestyle choices.

And what were the lifestyle choices that are linked to cancer?  The researchers list 20 separate things (in 8 broad groups) that are known to cause or are linked to cancer. They are: tobacco smoke (smoking or second-hand smoke), dietary factors (low-intake of fruit, non-starchy vegetables, and dietary fiber; and high intake of red and processed meat), overweight/obesity, alcohol, physical inactivity, solar ultraviolet radiation, certain infections (they list 7 infections, such as human papillomavirus, hepatitis B, hepatitis C), and reproductive factors (lack of breastfeeding, menopausal hormone therapy use, combined oral contraceptive use). Note that they found that the #1 most important lifestyle factor is tobacco smoke - and it accounted for about 23% of all preventable cancer deaths in Australia. From Medscape:

One Third of Cancer Deaths Could Be Prevented by Lifestyle

As we head into the festive season, many are looking forward to the tradition of "Eat, drink, and be merry." But as another research paper shows that more than a third of cancer deaths could be prevented by lifestyle, maybe a qualifier should be added:"celebration in moderation." The latest statistics come from Australia, where researchers note that 44,004 cancer deaths occurred in 2013. But an estimated 38% of these deaths and 33% of cancer diagnoses could have been prevented with healthy lifestyle choices, says a research team led by Louise Wilson, MEpi, at the QIMR Berghofer Medical Research Institute and the University of Queensland, Brisbane.

These cancer diagnoses and deaths were seen in Australians of all ages and are directly attributable to 20 known modifiable risk factors within eight categories that are established causes of cancer, the study authors say. The report is published in the February 2018 issue of the International Journal of Cancer.

Smoking was the leading cause of preventable cancer death in Australia in 2013 and accounted for 23% of all cancer deaths. ...Three other categories of modifiable risk factors — poor diet, overweight/obesity, and infections — accounted for 5% of cancer deaths each. In a fifth category, alcohol-related cancer accounted for 2.4% of deaths. Physical inactivity factors were responsible for 0.8% of cancer deaths, overexposure to ultraviolet radiation for 3.2% of cancer deaths, and, in the eighth category, reproductive or hormonal factors were linked to 0.4% of cancer deaths.

In the diet category, risk factors include low intake of fruit, nonstarchy vegetables, and dietary fiber and high intake of red and processed meat. In the infection category, seven cancer-causing agents, including human papillomavirus (associated with cancer of the vulva, vagina, penis, anus, oral cavity, and oropharynx) and Helicobacter pylori (noncardia stomach cancer), are included. Lack of breastfeeding, use of menopausal hormone therapy, and use of combined oral contraceptive use (breast and cervical cancer) are listed as preventable risk factors in the reproductive category.

These findings are in keeping with other research on the role of modifiable lifestyle-related risk factors in cancer prevention. As previously reported by Medscape Medical News, results from a large cohort study in the United States led researchers to conclude that 20% to 40% of cancer cases and related mortality could be prevented by not smoking, maintaining a healthy weight, and exercising regularly. In another report, results from a national online survey undertaken by the American Society of Clinical Oncology showed that, like their Australian counterparts, most US adults don't know alcohol and obesity are major risk factors for cancer[Original study.]

A dividing lung cancer cell. Lung cancer is associated with smoking. Credit: National Institute of Health (NIH). 

 

The message is clear from a recent study: older adults should get out and move, move , move (brisk walking is fine) - to lower the risk of early death. The older women engaging in the most moderate to vigorous activity had a 65% lower risk of early death during an average follow-up period of 2.3 years (when compared to the women with the least exercise).

How much exercise did the groups get? The least active had 6.8 minutes per day of moderate to vigorous exercise, and the most active had about 68 minutes/day of moderate to vigorous physical activity. The women wore a Fitbit type of device (an accelerometer) that measured their movements. Moderate to vigorous exercise was any movement that got the heart rate up a bit, made them sweat a little - and which could be brisk walking.

The study was done with older women (in their 70s), but one would think it also applies to men. Note: all-cause mortality means death from any cause (death in general). From Medscape:

Intense Exercise Tied to 65% Lower Death Risk in Older Women

Older women who engaged in the greatest amount of moderate to vigorous physical activity, such as brisk walking, were found to have a 65% lower risk of all-cause mortality compared with women who performed the least amount of such exercise, a new study reports. The researchers examined women in their early 70s in the Women's Health Study (WHS) who wore a triaxial accelerometer for 7 days to measure physical activity. The findings, by Dr I-Min Lee (Brigham and Women's Hospital, Boston, MA) and colleagues, were published November 6, 2017 in Circulation.

It's been known for a long time that physical activity is associated with lower mortality rates, Dr Lee told theheart.org | Medscape Cardiology.... Now that physical activity can be better measured using a research-grade triaxial accelerometer, the magnitude of the reduced risk of short-term death with recommended amounts of moderate to vigorous physical activity can be seen to be as strong as not smoking, Lee said. ... This study "reinforces the message that adults should strive to meet physical activity guidelines of 150 minutes of moderate or 75 minutes of vigorous exercise per week," Dr Alpa Patel (American Cancer Society, Atlanta, Georgia) who recently published a related article that showed benefits from walking told theheart.org | Medscape Cardiology.

From 2011 to 2015, 18,289 of 29,494 living women (63%) in the Women's Health Study agreed to participate in the current study.... The remaining 17,708 women were mailed a research-grade triaxial accelerometer (ActiGraph GT3X+, ActiGraph Corp) and asked to wear it on their hips for 7 days (but to take it off when sleeping or swimming) and then mail it back. 

The women spent a median of 8.4, 5.8, and 0.5 hours/day being sedentary, doing light physical activity, and doing moderate to vigorous physical activity, respectively. "The least active quartile were doing 8 minutes a day of moderate to vigorous . . . physical activity," Lee said, which was typically "brisk walking, anything that gets your heart rate up a little bit, gets you to sweat a little bit." The most active quartile did about 68 minutes/day of moderate to vigorous physical activity. During an average follow-up of 2.3 years, 207 women died. The total amount of physical activity was inversely related to the risk of all-cause mortality during follow-up, after adjustment for age and time spent wearing the device. 

Two studies (one in mice and one in humans) from researchers at the University of Illinois found that no matter what your diet - exercise changes the gut bacteria in a beneficial way. And when you go back to a sedentary lifestyle, your gut microbes change again and beneficial microbes such as short chain fatty acids (SCFAs), especially butyrates, decline. The effect was more pronounced in lean sedentary adults (as compared to obese sedentary adults).

Beneficial microbes that increased with exercise in humans were species of Faecalibacterium, Roseburia, Lachnospira, Lachnospiraceae, and Clostridiales. Faecalibacterium prausnitzii has been discussed in earlier posts as a beneficial keystone species in the gut (here, here, and here). What kind of exercises did they do? They did three supervised 30 to 60 minute moderate to vigorous intensity aerobic/endurance exercise sessions per week for 6 weeks, and they could use a cycle ergometer (stationary bicycle) or treadmill each session.

Besides beneficial microbial changes, 6 weeks of exercising resulted in improved body composition (total lean body mass, decreased body fat, increased bone mineral density), and an improvement in cardiorespiratory fitness. These changes reversed in everyone when they went back to 6 weeks of a sedentary lifestyle. Bottom line: get out and move, move, move. Your gut microbes and your body will thank you. From Science Daily:

Exercise changes gut microbial composition independent of diet, team reports

Two studies -- one in mice and the other in human subjects -- offer the first definitive evidence that exercise alone can change the composition of microbes in the gut. The studies were designed to isolate exercise-induced changes from other factors -- such as diet or antibiotic use -- that might alter the intestinal microbiota.

In the first study, scientists transplanted fecal material from exercised and sedentary mice into the colons of sedentary germ-free mice, which had been raised in a sterile facility and had no microbiota of their own. In the second study, the team tracked changes in the composition of gut microbiota in human participants as they transitioned from a sedentary lifestyle to a more active one -- and back again.

Recipients of the exercised mouse microbiota also had a higher proportion of microbes that produce butyrate, a short-chain fatty acid that promotes healthy intestinal cells, reduces inflammation and generates energy for the host. They also appeared to be more resistant to experimental ulcerative colitis, an inflammatory bowel disease.

In the human study, the team recruited 18 lean and 14 obese sedentary adults, sampled their gut microbiomes, and started them on an exercise program during which they performed supervised cardiovascular exercise for 30-60 minutes three times a week for six weeks. The researchers sampled participants' gut microbiomes again at the end of the exercise program and after another six weeks of sedentary behavior. Participants maintained their usual diets throughout the course of the study. Fecal concentrations of SCFAs, in particular butyrate, went up in the human gut as a result of exercise. These levels declined again after the participants reverted to a sedentary lifestyle.

The most dramatic increases were seen in lean participants, who had significantly lower levels of SCFA-producing microbes in their guts to begin with. Obese participants saw only modest increases in the proportion of SCFA-producing microbes. The ratios of different microbes in the gut also differed between lean and obese participants at every stage of the study, the researchers said. "The bottom line is that there are clear differences in how the microbiome of somebody who is obese versus somebody who is lean responds to exercise," Woods said. " [Original study in humans.]

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.]

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-upA 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.]

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 qualityhere, 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.]