Living with more than one long-term health condition is common. Worldwide, roughly one in three adults has two or more.1PubMed Central. The global burden of multiple chronic conditions: A narrative review In older adults and in wealthier countries like the US, it is the norm rather than the exception. The conditions also tend to arrive in recognizable groups rather than at random, so one diagnosis is often a clue about what to watch for next.
How Many Adults Have More Than One Condition
Doctors use “comorbidity” for any condition that sits alongside a main one. “Multimorbidity” means having two or more long-term conditions at once. Pooling surveys of ordinary adults living in the community, about 37% have two or more chronic conditions.2PubMed Central. Global and regional prevalence of multimorbidity in the adult population in community settings: a systematic review and meta-analysis Wealthier countries averaged about 38%, compared with about 30% in low- and middle-income countries.3PubMed Central. Prevalence of multimorbidity in community settings: A systematic review and meta-analysis of observational studies
On a chart, “comorbidity” is usually measured against one “index” condition, such as diabetes, so the question becomes what else a person with diabetes also has. “Multimorbidity” doesn’t center on any one condition; it simply counts how many long-term conditions a person has. Check whether a figure describes people with a particular diagnosis or all adults, because the share with extra conditions is very different in those two groups.
The number shifts because there is no single agreed list of which conditions count, and estimates can differ up to three-fold.4PubMed Central. The global burden of multiple chronic conditions: A narrative review UK studies range from 16% to 58%, and one study of urban South Asians found 9.4%.5PubMed Central. The global burden of multiple chronic conditions: A narrative review So “one in three” is a reasonable middle estimate, not a fixed fact.
Lists usually include high blood pressure, diabetes, arthritis, asthma, heart disease and depression. Some studies also count high cholesterol, obesity or chronic back pain, which pushes numbers up. Short illnesses like flu or a broken bone are not counted. Before comparing a headline figure with your own situation, check which list it used. US surveys generally give higher numbers than global averages, and survey answers depend on people knowing their own diagnoses.
A count also says nothing about severity. One person may have mild, well-controlled high blood pressure and arthritis, and another advanced heart failure and kidney disease, yet both are counted as having two conditions.
If you count anyone with at least one chronic condition, the share is far higher. More than half of US adults aged 18 to 34 have one.6Morbidity and Mortality Weekly Report. Chronic Conditions Among Adults Aged 18─34 Years — United States, 2019
How Age Changes the Odds
In children, studies find anywhere from about 1% to 17% have two or more chronic conditions.7PubMed Central. The magnitude of multimorbidity in childhood: a global systematic review That range reflects different choices about what counts, such as whether asthma, allergies, ADHD or learning difficulties are included. Many childhood conditions, asthma among them, are long-lasting but can improve as a child grows, so a count at one age may not hold later. By ages 18 to 34 in the US, about 22% have more than one.8Morbidity and Mortality Weekly Report. Chronic Conditions Among Adults Aged 18─34 Years — United States, 2019
Among US adults 65 and older, about 67% have two or more chronic conditions.9PubMed Central. Multimorbidity and Functional Limitations Among Adults 65 or Older, NHANES 2005–2012 That share is about 64% at ages 65 to 74 and about 71% at 75 and older.10PubMed Central. Multimorbidity and Functional Limitations Among Adults 65 or Older, NHANES 2005–2012 In one large group of older patients, the share climbed from 62% at 65 to 74 to about 82% at 85 and over.11PubMed. Multimorbidity in older adults A 2025 estimate found 93% of people 65 and older have at least one condition and 79% have two or more.12National Council on Aging. Top 10 Chronic Conditions Affecting Older Adults
Patients seen by doctors are more likely to have conditions recorded than people who rarely visit, so patient groups often show higher shares than surveys do. So the 79% and the 67% are not in conflict; they likely differ in which conditions were counted and how they were found.
Conditions pile up because many, like high blood pressure and arthritis, build slowly over decades. Each year adds more time for a new diagnosis without the old ones going away. More doctor visits in later life also mean more conditions get found and recorded.
If you or a parent is over 65, having several conditions is the typical situation, not unusual bad luck. It is worth asking for one clinician to oversee the whole picture rather than each condition separately. Bring a full list of diagnoses to every appointment, since specialists may not see each other’s notes.
Conditions That Tend to Come Together
The most consistent clusters are built around high blood pressure, heart disease, heart failure and diabetes.13PubMed Central. A systematic review and meta-analysis of disease clusters in multimorbidity These share risk factors and the same underlying damage to blood vessels, inflammation and insulin resistance.14PubMed Central. A systematic review and meta-analysis of disease clusters in multimorbidity Diabetes and chronic kidney disease appeared together in every stable cluster, because diabetes damages the small blood vessels the kidneys rely on.15PubMed Central. A systematic review and meta-analysis of disease clusters in multimorbidity Some clusters also included dementia, depression and anxiety, hinting at links between heart and brain health.16PubMed Central. A systematic review and meta-analysis of disease clusters in multimorbidity
This is why a diabetes diagnosis usually brings regular kidney and blood pressure checks. After a new diagnosis, ask which related conditions your doctor recommends screening for. Treating shared risk factors, such as blood pressure and weight, can help several conditions at once.
A cluster means conditions turn up together more often than chance would predict, not that one diagnosis guarantees the next. Many people with diabetes never develop kidney disease, especially when blood sugar and blood pressure stay well controlled.
In older adults, depression was the condition most often paired with others, linked to eight different diseases.17PubMed Central. The Prevalence of Disease Clusters in Older Adults with Multiple Chronic Diseases – A Systematic Literature Review Across a large national set of medical records, almost every mental health condition was linked to several physical ones.18Psychological Medicine. Co-occurrence between mental disorders and physical diseases: a study of nationwide primary-care medical records In developing and emerging countries, about 37% of people with a chronic physical illness also had a mental health condition.19PubMed Central. Co-morbidities of mental disorders and chronic physical diseases in developing and emerging countries: a meta-analysis
Low mood alongside a chronic illness is common and treatable, not just a normal reaction to accept. Mention changes in sleep, energy or interest to your doctor. Treating depression can make it easier to manage the physical conditions too.
Among older Australians, the most common trio was high blood pressure, asthma or hay fever, and arthritis.20PubMed Central. Multimorbidity and Comorbidity of Chronic Diseases among the Senior Australians: Prevalence and Patterns High blood pressure and arthritis are so common that they appear in nearly every frequent combination.21PubMed Central. Multimorbidity and Comorbidity of Chronic Diseases among the Senior Australians: Prevalence and Patterns
Studies that sort people into clusters don’t all find the same groups, because results depend on which conditions were counted and who was studied. The heart and metabolic group appears consistently, while smaller clusters, such as those including mental health or joint conditions, vary more. Your own combination may not match any published cluster, and that does not mean anything is wrong.
What Several Conditions Mean for Daily Life and Medicines
Each added chronic condition is linked with lower quality of life and more disability, with the biggest drop at four or more.22PubMed Central. Impact of Multimorbidity on Disability and Quality of Life in the Spanish Older Population People with three or more conditions were several times more likely to need help with basic daily tasks than those with one or two.23PubMed. The Association Between Multimorbidity and Quality of Life, Health Status and Functional Disability Depression and obesity weighed on nearly every area of daily wellbeing, from mobility to pain.24PubMed Central. Relative Impact of Multimorbid Chronic Conditions on Health-Related Quality of Life – Results from the MultiCare Cohort Study Pain, tiredness and low mood from several conditions can limit daily life even when no single condition is severe.
Taking five or more regular medicines becomes more common as conditions add up. Among older Ontarians, about 65% of women and 62% of men took five or more medicines by 2016.25PubMed Central. Sex differences in multimorbidity and polypharmacy trends: A repeated cross-sectional study of older adults in Ontario, Canada In frail older people receiving home care for chronic pain, the typical person took 9 prescribed drugs.26PubMed Central. High Prevalence of Multimorbidity and Polypharmacy in Elderly Patients With Chronic Pain Receiving Home Care are Associated With Multiple Medication-Related Problems Just two or three overlapping conditions can account for a third to a half of a very old person’s daily pills.27PubMed Central. Medication burden attributable to chronic co-morbid conditions in the very old and vulnerable
Each condition usually brings its own medicines, and the pills add up even when each prescription is reasonable on its own. Different specialists may each prescribe without seeing the full list, so the number grows unnoticed. More medicines raise the chance of side effects and interactions, and a side effect from one can be mistaken for a new condition and treated with another. Complicated schedules of pills at different times of day also make missed doses more likely.
A medication review helps. Bring every pill, supplement and inhaler to one appointment. Ask whether any medicine can be stopped or doses lowered, which drugs interact, and whether one condition’s treatment worsens another. Pharmacists can do this review too.
When treatments compete, tell your doctor which goals matter most to you, such as staying mobile or avoiding hospital. Not every guideline for every condition has to be followed when they conflict, and a care plan built around your priorities can reduce the medicine load.
Effects on Life Expectancy and Health Costs
In older adults with many conditions, the risk of dying was about three times that of people with none.28PubMed Central. Life expectancy estimates based on comorbidities and frailty to inform preventive care In one older population, multimorbidity cost an average of 7.5 years of life.29PubMed. Effect of Chronic Diseases and Multimorbidity on Survival and Functioning in Elderly Adults People with several conditions spent about 81% of their remaining years living with some disability.30PubMed. Effect of Chronic Diseases and Multimorbidity on Survival and Functioning in Elderly Adults
These are group averages, not predictions for one person. Risk depends on which conditions a person has and how well they are controlled; well-managed blood pressure or diabetes carries much less risk than untreated. Conditions can also worsen each other, as when diabetes and high blood pressure together strain the heart and kidneys more than either does alone. Treating one can be harder because of another, such as when kidney disease limits which heart medicines are safe, and recovery from surgery or infection can be slower.
Among people with multimorbidity, the healthiest lifestyles were linked to roughly 60% lower death risk than the least healthy.31PubMed Central. Healthy lifestyle and life expectancy in people with multimorbidity in the UK Biobank: A longitudinal cohort study Not smoking, staying active, eating well and keeping a healthy weight remain worthwhile after diagnosis. It is an association, and people who are very ill may be unable to exercise, so some of the gap may reflect health itself. You don’t need to reach the healthiest category to benefit; walking more or quitting smoking moves you in the right direction.
In England, the 32% of patients with two or more conditions accounted for about 55% of hospital care costs.32PubMed Central. Multimorbidity combinations, costs of hospital care and potentially preventable emergency admissions in England: A cohort study Treating diabetes cost about half again as much when heart disease was also present.33PubMed Central. The extra cost of comorbidity: multiple illnesses and the economic burden of non-communicable diseases Hospital patients with depression as well as a physical illness stayed about four days longer on average.34PubMed Central. Health-economic outcomes in hospital patients with medical-psychiatric comorbidity: A systematic review and meta-analysis
To cut avoidable costs and hospital trips, keep a shared list of conditions and medicines for every provider and ask about care coordination or chronic care management services. Book a follow-up with your regular doctor after any hospital stay.
Who Is More Likely to Have Several Conditions
Across general-population studies, about 45% of women versus 39% of men had multimorbidity.35PubMed Central. Sex differences in multimorbidity: a systematic review and meta-analysis Older men more often had heart disease, diabetes, lung disease and cancer, while women more often had osteoarthritis, osteoporosis, mood disorders and dementia.36PubMed Central. Sex differences in multimorbidity and polypharmacy trends: A repeated cross-sectional study of older adults in Ontario, Canada
Women generally live longer, so more of them reach the older ages when several conditions are most common. Women also more often have long-lasting conditions that limit daily life, while men more often have conditions that raise the risk of earlier death. A higher count in women therefore does not simply mean women are sicker overall.
People with low education had about 64% higher odds of multiple conditions than those with high education.37PubMed. Socioeconomic status and multimorbidity: a systematic review and meta-analysis Living in more deprived areas was consistently linked to more conditions, while evidence on income alone was mixed.38PubMed. Socioeconomic status and multimorbidity: a systematic review and meta-analysis Education is a marker for things that affect health over a lifetime, such as job type, income stability, health knowledge and access to care. Deprived areas likely bring more stress, poorer housing and food, and higher smoking rates, though studies cannot prove which matter most. These are group patterns, and many people with low education stay healthy while many with high education develop several conditions.
Many conditions go undiagnosed, from about 20% for dementia to 90% for depression and osteoarthritis.39PubMed. Under-diagnosis of common chronic diseases: prevalence and impact on human health Persistent pain, stiffness or low mood deserves a check rather than waiting. Groups with poorer access to care are the most likely to be missed.
Is Multimorbidity Becoming More Common
Among US adults, the share with two or more conditions rose from about 46% in 1988 to 1994 to about 60% in 2013 to 2014.40PubMed Central. Multi-morbidity Trends in United States adults, 1988–2014 Those with four or more rose from 12% to about 23%.41PubMed Central. Multi-morbidity Trends in United States adults, 1988–2014 In Ontario, the share rose from about 25% in 2003 to 32% in 2016, across men and women of all ages.42PubMed Central. Rising burden of multimorbidity and related socio-demographic factors: a repeated cross-sectional study of Ontarians
Several things push rates up. People live longer, so they have more years to develop conditions. Better testing finds conditions earlier, and rising obesity drives diabetes and high blood pressure.
A rising share does not by itself mean people are getting sicker at each age, since part of the rise may come from conditions being detected and recorded more often. The Ontario rise happened across all ages, which suggests it is not only a result of an aging population. The US and Ontario studies use different methods and conditions, so their percentages should not be compared directly, though both point the same way.
After COVID-19, about 14% of adults developed a new condition within six months, including heart and lung problems and type 2 diabetes.43BMJ. Comorbidities and covid-19 That points to a possible new route into multimorbidity. It does not mean most people with COVID-19 develop lasting conditions; most recover without a new diagnosis.