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A new study provides evidence for what so many people complain about - that after being treated for Lyme disease with several weeks of antibiotics - they feel that they are not cured, but instead still suffer from Lyme disease. Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted to a person during a tick bite. However, many medical professionals deny that a person can still have Lyme disease after antibiotic treatment, and instead call the lingering symptoms post-treatment Lyme disease syndrome (PTLDS). It is thought that between 10 to 20% of persons treated with antibiotics for Lyme disease have symptoms of PTLDS.

Hah! The Tulane University researchers found that yes, the live bacteria (B. burgdorferi spirochetes) can still be there in different organs of the body even after 28 days of antibiotic treatment. They studied late Lyme disease in both treated (with antibiotics) and untreated rhesus macaques - primates in which Lyme disease has effects similar to humans. Other studies have also found that the Lyme disease bacteria can evade treatment (here and here). From Medical Xpress:

Lyme bacteria survive 28-day course of antibiotics months after infection

Bay Area Lyme Foundation, a leading sponsor of Lyme disease research in the US, today announced results of two papers published in the peer-reviewed journals PLOS ONE and American Journal of Pathology, that seem to support claims of lingering symptoms reported by many patients who have already received antibiotic treatment for the disease. Based on a single, extensive study of Lyme disease designed by Tulane University researchers, the study employed multiple methods to evaluate the presence of Borrelia burgdorferi spirochetes, the bacteria that cause Lyme disease, before and after antibiotic treatment in primates.

The data show that living B. burgdorferi spirochetes were found in ticks that fed upon the primates and in multiple organs after treatment with 28 days of oral doxycycline. The results also indicated that the immune response to the bacteria varied widely in both treated and untreated subjects. "It is apparent from these data that B. burgdorferi bacteria, which have had time to adapt to their host, have the ability to escape immune recognition, tolerate the antibiotic doxycycline and invade vital organs such as the brain and heart," said lead author Monica Embers, PhD, assistant professor of microbiology and immunology at Tulane University School of Medicine.

"In this study, we were able to observe the existence of microscopic disease and low numbers of bacteria, which would be difficult to 'see' in humans but could possibly be the cause of the variable and nonspecific symptoms that are characteristic of post-treatment Lyme disease syndrome. Although current antibiotic regimens may cure most patients who are treated early, if the infection is allowed to progress, the 28-day treatment may be insufficient, based on these findings," Embers said.

The findings also demonstrated: All subjects treated with antibiotics were found to have some level of infection 7 - 12 months post treatment. Despite testing negative by antibody tests for Lyme disease, two of 10 subjects were still infected with Lyme bacteria in heart and bladder. Lyme bacteria which persist are still viable.

To better elucidate previous animal studies demonstrating that some B. burgdorferi bacteria survive antibiotics, the study explored Lyme disease infection in rhesus macaque primates treated with antibiotics and a control group who were also infected but not treated. 

In the study, ticks carrying B. burgdorferi spirochetes fed on ten primates. Four months post infection, half of the primates (five) received the antibiotic doxycycline orally for 28 days at a proportional dose to that used in human treatment...... The results show: Few subjects displayed a rash. Although all subjects were infected, only one of the 10 displayed a rash with central clearing, the classical "bulls-eye" rash. ... Organs may be infected even if antibody tests are negative...... Intact spirochetes were found in three of five treated and four of five untreated subjects based on xenodiagnosis results 12 months after the tick bite.

Immune responses to B. burgdorferi varied greatly posttreatment .... This is significant because it demonstrates that subjects infected with the same strain of B. burgdorferi may have different immune responses to the same antigen. And, because humans, like primates, are genetically diverse, it underscores that testing antibody responses may be inherently unreliable as a singular diagnostic modality for Lyme disease.

Widespread and variable microscopic disease was observed in all infected subjects, despite antibiotic treatment. Compared to uninfected subjects of the same age, infected subjects in this study (treated and untreated) demonstrated inflammation in and around the heart, in skeletal muscles, joints, and the protective sheath that covers the brain, and near peripheral nerves. Rare, but intact B. burgdorferi spirochetes were found in the tissues of both the treated and untreated subjects. In two subjects treated with doxycycline, multiple Lyme bacteria were observed in the brain tissue [Original study.]

What does it take to live to 100 in relatively good health? Are there common psychological traits? A study looked at 29 rural Italians aged 90 to 101 and their 51 younger family members to try to answer that question. They found that the elderly  participants had worse physical health but better mental well-being than their younger family members.

The older adults had a positive attitude or positivity (resilience and optimism), they worked hard, and had strong bonds with family and religion. They also had a strong need for control (family members called them "domineering") and a love of the land. The researchers summarized: "Exceptional longevity was characterized by a balance between acceptance of and grit to overcome adversities along with a positive attitude and close ties to family, religion, and land, providing purpose in life." From Science Daily:

Common psychological traits in group of Italians aged 90 to 101

In remote Italian villages nestled between the Mediterranean Sea and mountains lives a group of several hundred citizens over the age of 90. Researchers at the University of Rome La Sapienza and University of California San Diego School of Medicine have identified common psychological traits in members of this group. The study, publishing in International Psychogeriatrics, found participants who were 90 to 101 years old had worse physical health, but better mental well-being than their younger family members ages 51 to 75.

"The main themes that emerged from our study, and appear to be the unique features associated with better mental health of this rural population, were positivity, work ethic, stubbornness and a strong bond with family, religion and land." There were 29 study participants from nine villages in the Cilento region of southern Italy. 

"The group's love of their land is a common theme and gives them a purpose in life. Most of them are still working in their homes and on the land. They think, 'This is my life and I'm not going to give it up,'" said Anna Scelzo, first author of the study with the Department of Mental Health and Substance Abuse in Chiavarese, Italy. Interview responses also suggested that the participants had considerable self-confidence and decision-making skills. "This paradox of aging supports the notion that well-being and wisdom increase with aging even though physical health is failing," said Jeste, also the Estelle and Edgar Levi Chair in Aging and director of the Sam and Rose Stein Institute for Research on Aging at UC San Diego.

"We also found that this group tended to be domineering, stubborn and needed a sense of control, which can be a desirable trait as they are true to their convictions and care less about what others think," said Scelzo. "This tendency to control the environment suggests notable grit that is balanced by a need to adapt to changing circumstances." [Original study.

Rural village in the region of Cilento,  Italy. Credit: Wikipedia.

 The findings of a large study from Denmark were a disappointment for those hoping that women taking or using low dose hormonal birth control (pills, IUD) would not show an increase in breast cancer (like the old higher dose birth control pills). This study found a small increase in the risk of breast cancer with the use of modern birth control pills and with a progestin-only intrauterine device. They pointed out that the biggest risk was in those using hormonal methods for over 10 years and in their 40s (most of the breast cancer cases occurred in this group of women). The risk goes up the longer one uses hormonal contraception.

Due to smaller numbers of women using a birth control patch, vaginal ring, and implants - they were unable to say one way or another if these also are linked to a higher incidence of breast cancer. But the sense from the researchers is that all hormonal contraception has a slight increase in risk of breast cancer. How big an increase in risk? There is a 20% increased risk overall, but the actual numbers are fairly small - 13 per 100,000 women or approximately 1 extra breast cancer for every 7690 women using hormonal contraception for 1 year. From Medical Xpress:

Small risk of breast cancer seen with hormone contraceptives

Modern birth control pills that are lower in estrogen have fewer side effects than past oral contraceptives. But a large Danish study suggests that, like older pills, they still modestly raise the risk of breast cancer, especially with long-term use. Researchers found a similar breast cancer risk with the progestin-only intrauterine device, and they couldn't rule out a risk for other hormonal contraceptives like the patch and the implant.

But the overall increased risk was small, amounting to one extra case of breast cancer among 7,700 women using such contraceptives per year. Experts who reviewed the research say women should balance the news against known benefits of the pill - including lowering the risk of other cancers.

Researchers analyzed health records of 1.8 million women, ages 15 to 49, in Denmark where a national health care system allows linking up large databases of prescription histories, cancer diagnoses and other information. Results were published Wednesday in the New England Journal of Medicine. Novo Nordisk Foundation funded the research, but played no role in designing the study.

Current and recent use of hormonal contraceptives was associated with a 20 percent increased risk of breast cancer. Risk increased with longer use, from a 9 percent increase in risk with less than a year of contraceptive use to a 38 percent increase after more than 10 years of use. Digging further, the researchers found no differences among types of birth control pills. Because of fewer users, the results for the patch, vaginal ring, implant and progestin shot were less clear, but the analysis didn't rule out an increased breast cancer risk for those methods. [Original study.]

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.]

This is interesting, that blood pressure naturally starts lowering in the 14 to 18 years prior to death in people 60 years or older - whether they are healthy, have hypertension, have heart disease, take hypertension medicines or not.

The researchers analyzed 20 years of medical data for patients in the United Kingdom, and while everyone's blood pressure dropped for more than a decade before death, the decreases were "steepest in patients with hypertension, dementia, heart failure, and late-life weight loss". From Science Daily:

Blood pressure declines 14 to 18 years before death

Blood pressure in the elderly gradually begins to decrease about 14 or so years before death, according to a new study published today in the Journal of the American Medical Association Internal Medicine. Researchers from UConn Health and the University of Exeter Medical School in the U.K. looked at the electronic medical records of 46,634 British citizens who had died at age 60 or older. The large sample size included people who were healthy as well as those who had conditions such as heart disease or dementia.

They found blood pressure declines were steepest in patients with dementia, heart failure, late-in-life weight loss, and those who had high blood pressure to begin with. But long-term declines also occurred without the presence of any of these diagnoses.

Doctors have long known that in the average person, blood pressure rises from childhood to middle age. .... Some studies have indicated that blood pressure might drop in older patients and treatment for hypertension has been hypothesized as explaining late-life lower blood pressures. But this study found blood pressure declines were also present in those without hypertension diagnoses or anti-hypertension medication prescriptions. Further, the evidence was clear that the declines were not due simply to the early deaths of people with high blood pressure. [Original study.]

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.]

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.

The researchers point out in the study (published in The BMJ) that: "Roasted coffee is a complex mixture of over 1000 bioactive compounds, some with potentially therapeutic antioxidant, anti-inflammatory, antifibrotic, or anticancer effects that provide biological plausibility for recent epidemiological associations. Key active compounds include caffeine, chlorogenic acids, and the diterpenes, cafestol and kahweol." Impressive. [All posts about coffee.] 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 dementiaHowever, 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.)

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.

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.]

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.]