What Do Microbes Have to Do with How We Age? Everything, Actually

From the moment we are born, we begin to die. Aging is a universal but uniquely personal experience. It scares us, bullies us, and motivates us to live better. Because we, as a species, are living longer and longer (more than eighty years nowadays in most high-income countries), every one of us has even more time than ever before to grapple with aging and mortality. Despite what advertisements and doctors may tell us, there is no way to simply “turn back the clock,” but we still try to delay the inevitable. We all search for ways to prolong our lives and preserve our bodies—these complex machines made of muscle, bone, and a host of other tissues, our minds, our hearing and eyesight, even our looks. Pharmacy and grocery store aisles—as well as social media—are full of anti-aging products, ranging from serums and creams to fight wrinkles and banish spots, to vitamins and supplements promising an elusive “youthful glow.”

Scientific studies suggest myriad ways to intervene in the aging process, including antioxidants, calorie restriction, hormone supplements, and a host of dermatological procedures and treatments. Although many of these methods have been touted as glamorous and high-tech, one of the most exciting frontiers of current aging science involves the oldest life forms on Earth: microbes.

There are more microbes in a gram of feces than there are people on the planet.

Contrary to the cutting-edge scientific inventions we’re using to make alternative time-reversers, these bacteria have been around for more than 3.5 billion years, from a time when our planet was covered in oceans that regularly reached boiling point. Our climate has changed dramatically, but microbes are still everywhere: in the air you breathe (they actually made the original oxygen in the atmosphere), on the chair you sit in, and in the food in your fridge. In fact, there are more microbes in a gram of feces than there are people on the entire planet!

Microbes are our constant companions throughout life. Commonly known as germs, they come in many forms, including bacteria, viruses, protozoa, algae, and fungi. While we often blame them for disease, we have only recently realized they are, in fact, absolutely essential for a healthy life. We could not exist without them. But what do microbes have to do with aging? Everything, actually.

Aging is a natural process that occurs in all biological species, though for some, it happens faster than for others. Biologically, we humans hit our prime at around age twelve. In other words, if your physiology (meaning your body and its functionality) remained at that age, you would live more than 1,000 years! After twelve, the chance of dying doubles every eight years.

And yet our species somehow beats these odds with increasing success. We spoke to Anne Martin-Matthews, professor emerita of sociology at the University of British Columbia and former scientific director for the Institute of Aging established by the Canadian Institutes of Health Research. She commented on our current staggering, and unprecedented, aging population: “Over the forty years of my career studying aging, we never anticipated how the field would be shaped by the extended longevity of the population. As recently as a decade or so ago, much of our research focused on ‘older people’ in their seventies and the ‘oldest old’ in their eighties. Now we all personally know a seventy-three-year-old with a ninety-five-year-old mother, or an eighty-two-year-old woman concerned about her elderly husband and with a 105-year-old parent still alive!”

The advent of vaccinations, antibiotics, and improved sanitation, beginning in the early 1900s, dramatically reduced the number of childhood deaths, as well as deaths due to infectious diseases. This resulted in a major increase in longevity worldwide: life expectancy increased from thirty-two years in 1900 to seventy-one years in 2021, with Japan’s average currently coming in highest at eighty-four! Martin-Matthews noted that the number of centenarians (people older than 100) continues to increase worldwide, along with more supercentenarians (those older than 110). This is one of the most significant social transformations of the twenty-first century.

While virtually every country in the world has growing numbers of older people, chronic ailments, such as obesity, type 2 diabetes, asthma, and inflammatory bowel diseases, are also rapidly on the rise worldwide. Far from being limited to high-income regions of the world, chronic diseases are accelerating in developing countries. The number of people in low- and middle-income countries with diabetes, for example, will increase by more than 2.5-fold: from 84 million in 1995 to more than 228 million in 2025. The World Health Organization (WHO) estimates that the global burden of chronic disease had risen to 74 percent in 2024, up from approximately 46 percent in 2001. Almost three quarters of all deaths worldwide, in 2024, were attributable to chronic diseases.

These conditions plague many individuals’ health and reduce quality of later life. In terms of incidence (i.e., the number of people affected), cardiovascular disease and brain diseases, such as Alzheimer’s, Parkinson’s, and dementia, are on a dramatic upward trajectory in our society. But despite more than twenty years of intense research, Martin-Matthews reflected there is still no “silver bullet” to address Alzheimer’s disease and related dementias: “Research has primarily focused on the brain and its structural changes. Yet the reality is that we have not been able to find effective prevention or treatment measures. Multiple billions of dollars of research investment later, we’re coming to understand that the issue is much more complex. We clearly need to look elsewhere. Perhaps the microbiome plays a role—maybe to solve problems in the brain, we need to look at the gut and other areas of the body where microbes are involved.” Martin-Matthews admits she is no microbe expert—in fact, she confessed at the beginning of our interview that she is quite the opposite.

And yet, as a sociologist and social scientist, she is clued in to possible microbial interactions. Microbes affecting our brains, as well as other distinct bodily and environmental sites, are ripe for investigation given that they offer immense potential to better understand aging. Researchers with the openness of Martin-Matthews have already drawn remarkable connections between the microbiome and conditions such as obesity, type 2 diabetes, asthma, and inflammatory bowel diseases, in one way or another.

They have also found links to many other normal physiological changes associated with aging, such as loss of bone and muscle mass and skin wrinkling. This research involves microbial effects well beyond the stronghold of our gut, in important body sites, such as the brain, heart, and bones, as well as critical human environments, including hospitals and nursing homes. By better understanding our everyday environmental microbes, we believe we may be able to strategically manipulate them so that we can live healthier and longer lives.

People over the age of seventy have radically altered microbial communities from when they were younger. The composition of microbiota (micro-organisms in a particular environment) also shifts, which may detrimentally affect older people. For example, as we will see later, age causes an increase in inflammatory microbes and a decrease in helpful microbes that dampen the immune system. Collectively, this results in an increase in low-grade inflammation throughout the body causing tissue damage, a process called “inflammaging.” These changes can lead to greater susceptibility to diseases and a general decline in health. Knowing that microbes are at the heart of general body decline is a great discovery for science—and for all of us—and highlights the critical need to maintain and enhance our microbes as we age.

Take sleep, for instance. We spend about a third of our lives sleeping—that’s around twenty-six years for the average person. Sleep is a basic biological need that plays a critical role in our lives and, more recently, has been recognized as a key part of healthy living and aging. It is a necessary time to enable our bodies to rest, repair, and recover from the day. Contrary to popular belief, your brain is actually active during sleep, working to process and consolidate the day’s memories and improve cognitive function. Sleep helps to stabilize your mood and reduce stress. Your blood pressure and heart rate fall, muscles repair, and tissues regenerate. The immune system gets a boost, and your body conserves energy, which helps with metabolic balance. Long story short, sleep is essential to every process in the body and related to every aspect of health. And several recent studies link the microbiome to sleep and sleep quality.

More than a third of Americans report getting less than seven hours of sleep a night.

How much sleep do you need? It varies with age. Newborn babies sleep a lot (fourteen to seventeen hours a day), school-age children need about nine to eleven hours, and teenagers eight to ten hours. The National Sleep Foundation recommends that the average adult (eighteen to sixty-four years of age) requires seven to nine hours to feel well rested. It is a myth that older adults (sixty-five and up) need less sleep: seven to eight hours is still recommended. But there are changes in sleep patterns and quality that are common among older ages, resulting in more fragmented sleep as well as increased napping. Older adults tend to get tired earlier in the evening, wake up earlier, and have less REM and slow wave sleep (often referred to as deep sleep).

Unfortunately, more than a third of Americans report getting less than seven hours of sleep a night. About 30 percent of adults have symptoms of insomnia. While once an all-nighter may have been viewed as a badge of honour, we now recognize that sleep deprivation has major impacts. Lack of sleep is linked to increased risk for numerous health conditions, including obesity, diabetes, hypertension, heart disease, stroke, anxiety, depression, and dementia. The three pillars of health—nutrition, exercise, and sleep—are tightly connected. If you don’t sleep well, you tend not to eat as well (e.g., junk food cravings can increase), and often the last thing you want to do is hit the gym. Furthermore, sleep apnea (a potentially serious sleep disorder in which breathing repeatedly pauses while sleeping), which affects between 9 to 38 percent of the United States’ population, is associated with increased Alzheimer’s risk. REM sleep behaviour disorders (vocally and/or physically acting out your dreams) are a major risk factor for Parkinson’s.

The past few years have seen an explosion in studies linking the microbiome to sleep. We’ve known for a while that the microbiome is involved in regulating circadian rhythms, which are key to sleep. It now appears that microbes have their own circadian rhythms that may interact with the body’s circadian rhythms and potentially affect sleep. These microbial rhythms are affected by diet (which influences microbiome composition) and when you eat. We also know that microbes produce neurotransmitters, such as serotonin and gamma-aminobutyric acid (GABA), which play a role in regulating mood and relaxation and, of course, sleep. And finally, the microbiome has a large impact on the immune system and inflammation, which, in turn, impacts sleep quality.

The connection between the microbiome and sleep works both ways. For example, you are fasting when asleep, so this affects bacterial growth in the gut, as there are no new nutrients during those hours. Poor sleep can affect the microbiome in detrimental ways. Lack of sleep increases stress, thereby increasing cortisol (a steroid hormone produced by the adrenal glands), which can have a major impact on the microbiome through its inflammatory activity. Lack of sleep can also lead to increased cravings for carbs, sugars, and trans fats, which we know alter the microbiome. Animal experiments show that if you significantly disrupt the microbiome, you disrupt sleep rhythms. Mice fed broad-spectrum antibiotics had changes in their sleep patterns, including disrupted REM sleep and changes in the neurotransmitter serotonin, which is associated with regulating sleep–wake cycles.

Evidence of the connection between the microbiome and sleep in humans, especially through the gut–brain microbiome axis, is increasing. A general (and not surprising) consensus emerging among microbiologists is that poor sleepers have a dysbiotic microbiome, but this varies from person to person. There is no single micro-organism linked to good sleep; like many things microbiome-related, a diverse collection of beneficial microbes is associated with good sleep. The other prevalent consensus is that, although we know beneficial microbiomes are associated with better sleep, we don’t know whether they are causing better sleep. However, more and more studies are showing that, by changing the microbiome (e.g., through diet, probiotics, or fecal transfers), one can promote good sleep. So, using the microbiome to enhance sleep shows significant promise.

One study looked at “social jet lag,” which involves waking for work at specific hours during the week, then staying up late and sleeping in on the weekend. In a cohort of 934 people, researchers found that just a ninety-minute difference in the timing of the midpoint of sleep (e.g., sleeping ninety minutes later on the weekend) was associated with changes in the gut microbiome. Social jet lag was also associated with lower overall diet quality and higher sugar intake, which also influence microbes.

Sleep deprivation is becoming more and more common across society and is known to dysregulate inflammatory processes and cognition. Given the microbiome’s role in these processes, it is not surprising to see that sleep deprivation impacts our microbiomes. In a study of twenty-five participants, each participant was kept awake for forty hours following eight hours of sleep. In addition to expected poorer cognition performances due to sleep deprivation, they also found decreases in diversity in the microbiome. Continued episodes of sleep deprivation also had increased effects on microbial diversity.

It is estimated that over a billion people worldwide have obstructive sleep apnea (OSA), which is defined as breathing being interrupted for greater than ten seconds at least five times an hour, resulting in decreased sleep quality. This condition is associated with increased risk of cardiovascular diseases and diabetes, as well as a decreased life expectancy. It is also associated with obesity and significantly increased snoring. People (and experimental mice) with OSA have a disrupted microbiome, including a reduction in SCFA producers and altered inflammatory responses. Further, changes in the microbiome have been observed among people with narcolepsy through altered microbial diversity.

Patients with chronic fatigue syndrome also had a dysbiotic microbiome. Again, with all of these sleep issues, it has not been established that the microbiome is involved in the problem or whether secondary changes occur as a result of the problem. However, there are certainly strong hints that the microbiome is involved.

• Sure, Ultra-Processed Foods Are Bad. But How Does That Help Anyone?
• How I Tried to Stop Snoring, Fix My Sleep Habits, and Confront My Mortality
• Is Everyone Else Grinding Their Teeth Too?

Given all that we know about the potential role of the microbiome in sleep, it begs the question: If we enhance our microbiome, can we improve our sleep? Fortunately, there are significant data to indicate that, yes, better sleep is indeed possible (along with all the other benefits a healthy microbiome brings).

The first obvious way is to improve diet, such as by increasing intake of fibre and fermented foods. In a 2018 study of 2,068 participants, researchers found that following a Mediterranean-style diet was associated with adequate sleep and less insomnia. In a 2019 study of 1,314 individuals, better adherence to the Mediterranean diet was associated with a higher likelihood of overall adequate sleep quality. Higher fibre increases beneficial SCFAs and serotonin, both associated with enhanced sleep. Other dietary changes that can help enhance sleep include decreasing alcohol consumption, avoiding caffeine and other stimulants right before bed and reducing intake in general, eating meals at regular times (which enhances circadian rhythm) and not right before bedtime, and staying hydrated.

There is growing evidence that probiotics may enhance sleep.

Perhaps the strongest proof that the microbiome is associated with improved sleep comes from fecal material transfer (FMT) experiments done on people with irritable bowel syndrome (IBS). It is well established that an altered dysbiotic gut microbiome is associated with IBS. Sleep disturbances and changes in sleep patterns are also associated with IBS. In human FMT studies where healthy feces were transferred into IBS patients, improvements were seen in sleep (in addition to depression and anxiety). Related studies have put human feces into germ-free animals with similar results. Collectively, this work suggests that the microbiome can have direct effects on sleep.

There is growing evidence over the past couple of years that probiotics may enhance sleep. Several studies indicate that Lactobacillus species may enhance sleep. L. brevis administration is known to increase microbial metabolites associated with sleep enhancement (but hasn’t been directly shown to improve sleep). A heat-inactivated (i.e., killed) administration of L. gasseri seemed to improve sleep problems. A meta-analysis of six studies involving 343 healthy adults who consumed L. gasseri daily showed significant improvement in sleep.

A recent randomized, double-blind, placebo-controlled trial (the gold standard clinical study, as neither the participants nor the scientists know which randomly selected group any one individual belongs to) using a multi-strain probiotic consisting of Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01, and Bifidobacterium longum 04 (all common, commercially available, probiotic strains) was tested in seventy healthy individuals. They took the probiotic mixture for six weeks and then, after a further three weeks, were tested for sleep parameters. Researchers concluded that this probiotic mixture improved the ability to fall asleep faster and experience fewer sleep disturbances, resulting in overall improved sleep quality.

A 2024 study showed that a single probiotic strain, Bifidobacterium longum 1714, was able to improve sleep. This probiotic has already shown positive effects on stress, anxiety, and depressive symptoms. In the randomized, double-blind, placebo-controlled study involving eighty-nine adults with impaired sleep quality, participants were given a capsule of 1 billion colony-forming units of B. longum 1714 that also included corn starch (a prebiotic) and magnesium stearate (a muscle relaxant) daily for eight weeks. The strain significantly improved sleep quality and reduced daytime dysfunction due to sleepiness, as well as improving social functioning and vitality compared to the controls. The authors claim that this is the only probiotic strain that also seems to boost mental wellness among recipients. Although the mechanism(s) by which this probiotic may work were not established, it is an excellent trial indicating that this probiotic may enhance not only sleep but also overall mental health.

All of which is to say: a healthy microbiome may promote healthy sleep, which, in turn, promotes healthy aging.

Adapted and excerpted, with permission, from The Microbiome Master Key: Harness Your Microbes to Unlock Whole-Body Health and Lifelong Vitality by B. Brett Finlay and Jessica M. Finlay, published by Douglas & McIntyre, 2025.