How Do Life Expectancy and Healthy Life Expectancy Differ?

In many countries, life expectancy (the average number of years that a person can expect to live) has increased over the last 50 years. However, there can be big differences between life expectancy and healthy life expectancy (the average number of years that a person can expect to live in good health). For example, in Japan, one out of every two babies born in 2023 is now expected to live until the age of 100 years; however, current healthy life expectancy is approximately 9 years less than life expectancy for men and 12 years less for women.

A number of research studies are being conducted to help us better understand how to narrow the gap between healthy life expectancy and life expectancy. Increased prevalence of obesity and levels of physical activity have both been shown to be significant factors. In addition, recent research has suggested that gut frailty may also be involved.

What Is Gut Frailty?

People are described as being frail when they are between the states of being healthy and needing care. As people age, they become frail when they have reduced physical (muscle) and mental strength and health, and the risk that they will need assistance with daily activities begins to increase. The term “gut frailty” refers to the functions of the gastrointestinal system becoming “weakened”. Recent research has shown that gut frailty can be a precursor to overall frailty, can worsen the symptoms and severity of some diseases, and also causes chronic inflammation.

What Are the Symptoms of Gut Frailty?

The following symptoms are considered to be potential indicators of gut frailty:

• Pain or discomfort in the abdomen;
• Constipation (finding it hard to poo or going to the toilet less often than usual) or diarrhea (when the poo is loose and watery, and needing to go to the toilet more often than usual);
• Abdominal bloating;
• Stress-related symptoms;
• Weight loss or decreased appetite.

What Is the Link between Constipation and Frailty?

Among the symptoms listed above, constipation seems to be particularly associated with frailty. Studies have shown that people who experience constipation are at greater risk of developing a number of conditions that include disorders affecting the heart and blood vessels (cardiovascular disorders), chronic kidney disease, and neurodegenerative disorders such as Parkinson’s disease. Although constipation is often thought to simply be a result of the colon not functioning properly (the colon is the part of the digestive system where water and some other nutrients are absorbed into the body from our partially digested food), it can actually be a symptom that disease is developing and can make it worse.

In a study that compared the cognitive decline (changes in cognitive function that are considered to be a normal part of the aging process, like difficulties with multitasking and sustaining attention, and an overall slowing of thinking speed) of elderly people who experienced constipation with people who did not, the rate of cognitive decline was 2.7 times faster among the people with constipation. Similarly, another study reported that loss of muscle and strength as a person gets older (known by the medical term “sarcopenia”) was significantly greater in a group with constipation symptoms compared with a group without them.

What Causes Gut Frailty?

The exact causes of gut frailty aren’t yet known but they are thought to be a combination of reduced secretion of mucus inside the gut, thought to be a key factor in the early stages of gut frailty’s development, and an imbalance in the community of microbes that live in the gut (termed “dysbiosis”) among other factors. The guts of healthy adults contain more than 1,000 different species of microbes, collectively known as the gut microbiome. Although the majority of the microbes are beneficial to us, breaking down indigestible fibers and producing essential nutrients that you would not otherwise be able to get, some are pathogenic (cause disease). If the numbers of “good” bacteria decrease, it becomes possible that the “bad” bacteria will increase in number and overrun the population of good microbes.

Research has shown that the gut microbiome and the immune system are intimately linked. The gut microbiome communicates with the immune system and, if it is healthy, effectively helps it to increase the number of immune cells that dial down the immune system responses that cause inflammation. It is also becoming apparent that the gut microbiome and the nutrients that it produces influence aging. One study reported that people with a low level of gut microbiome diversity had a lower rate of survival compared with people with a higher level when compared after 4 years.

How Can Gut Frailty Be Prevented?

Research investigating how gut frailty can be prevented is ongoing. Potential approaches include dietary changes, medications, next-generation prebiotics (plant fibers that help “good” bacteria to thrive in your gut) and probiotics (live bacteria and yeasts, promoted as having health benefits, that are usually taken as supplements or added to yoghurts), and fecal microbiota transplantation (FMT, also known as poo or stool transplantation). FMT works by transferring the microbiome from a healthy donor to the intestines of a recipient, usually in capsule or liquid form, and has shown to have positive effects lasting several years in patients with irritable bowel syndrome.

Although the concept of gut frailty is not yet widely recognized, better understanding of how gut frailty affects our health will open up the possibility of developing new preventive and therapeutic interventions that focus on the gastrointestinal system, with the aim of helping us to lead healthier lives well into old age.

Note: The author of this paper make a declaration about grants, research support, consulting fees, lecture fees, etc. received from pharmaceutical companies. It is normal for authors to declare this in case it might be perceived as a conflict of interest. For more detail, see the Conflict of Interest Statement at the end of the paper.