The most common health problems range from heart disease and diabetes to depression and chronic lung conditions. In the United States alone, over 76% of adults (roughly 194 million people) live with at least one chronic health condition, and that number climbs with age: about 6 in 10 young adults, 8 in 10 middle-aged adults, and 9 in 10 older adults have at least one. Here’s a closer look at the health problems that affect the most people and what actually happens in your body when they develop.
Heart Disease and Stroke
Heart disease is the single deadliest health problem in the world, killing roughly 9 million people each year. The most common form, called ischemic heart disease, happens when fatty deposits build up inside the arteries that supply blood to your heart. Over time, these deposits narrow the arteries, reducing blood flow and forcing your heart to work harder. The same process can affect arteries leading to your brain, which is how strokes occur.
Several everyday factors drive this damage. High blood pressure puts constant extra force on the walls of your blood vessels, weakening them over time. High cholesterol contributes to plaque buildup. High blood sugar, common in people with diabetes, triggers inflammation that damages the inner lining of blood vessels. These risk factors often cluster together, especially in people carrying excess weight, creating a compounding effect where each problem accelerates the others.
Type 2 Diabetes and Prediabetes
Type 2 diabetes develops when your body can no longer manage blood sugar effectively. Nearly 9 in 10 people with type 2 diabetes have overweight or obesity. Left unmanaged, persistently high blood sugar damages blood vessels and nerves throughout the body, leading to complications like kidney disease, vision loss, and poor wound healing, particularly in the feet.
A simple blood test called A1C measures your average blood sugar over the past two to three months. A normal result is below 5.7%. Between 5.7% and 6.4% is considered prediabetes, a warning stage where blood sugar is elevated but not yet in the diabetes range. At 6.5% or above, the diagnosis is diabetes. The prediabetes stage is significant because lifestyle changes at this point, like increasing physical activity and losing a modest amount of weight, can delay or prevent progression to full diabetes.
Obesity and Its Chain of Effects
Obesity is less a single disease and more a catalyst for many others. Carrying excess weight raises your risk for type 2 diabetes, high blood pressure, heart disease, stroke, fatty liver disease, and several types of cancer. It also takes a physical toll on your joints: obesity is a leading risk factor for osteoarthritis in the knees, hips, and ankles because of the extra pressure placed on cartilage. Gout, a painful form of arthritis caused by uric acid crystals building up in joints, is also more common in people with obesity.
A cluster of problems called metabolic syndrome ties many of these risks together. You’re diagnosed with metabolic syndrome if you have at least three of the following: a large waist size, high triglycerides, high blood pressure, high fasting blood sugar, and low levels of HDL (“good”) cholesterol. Having this combination dramatically increases your chances of heart disease, diabetes, and stroke beyond what any single factor would predict.
Chronic Lung Disease
Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide. It includes conditions like emphysema and chronic bronchitis, which gradually destroy lung tissue and make breathing progressively harder. Smoking is the best-known cause, but air pollution plays a major role as well.
Fine particulate matter, the tiny particles found in vehicle exhaust, wildfire smoke, and industrial emissions, can penetrate deep into the lungs and even enter the bloodstream. Short-term exposure can trigger asthma attacks, reduce lung function, and cause respiratory infections. Long-term exposure increases the risk of COPD, lung cancer, and even heart disease and stroke. The particles cause inflammation and damage to cells throughout the body, not just in the lungs.
Cancer
Lung cancer is the deadliest cancer globally, ranking among the top 10 causes of death worldwide. But cancer as a broad category encompasses hundreds of different diseases, each involving cells that grow and divide uncontrollably. Risk factors vary by type: smoking for lung cancer, UV exposure for skin cancer, obesity for several cancers including colorectal and breast.
Screening catches some cancers early, when they’re most treatable. For colorectal cancer, the U.S. Preventive Services Task Force recommends screening starting at age 45 and continuing through age 75. Options range from a simple annual stool test you can do at home to a colonoscopy every 10 years. Between ages 76 and 85, screening becomes an individual decision based on your health and preferences.
Depression and Anxiety
Mental health conditions are among the most widespread health problems on the planet. In 2021, nearly 1 in 7 people worldwide, about 1.1 billion, were living with a mental disorder. Anxiety disorders affected 359 million people, including 72 million children and adolescents. Depression affected roughly 280 million people globally.
These aren’t simply “feeling stressed” or “being sad.” Depression involves persistent changes in mood, energy, sleep, appetite, and the ability to concentrate or find pleasure in things you used to enjoy. Anxiety disorders involve excessive worry or fear that interferes with daily functioning, sometimes accompanied by physical symptoms like a racing heart, muscle tension, or difficulty breathing. Both conditions are highly treatable with therapy, medication, or a combination, yet a large percentage of people with these disorders never receive care.
Alzheimer’s Disease and Dementia
Alzheimer’s disease is a progressive brain disease that destroys memory and thinking skills over time. It ranks among the top 10 causes of death globally, and its impact extends far beyond the person diagnosed, often requiring years of full-time caregiving from family members.
Early warning signs go beyond the occasional forgotten name. They include repeating questions or forgetting recently learned information, trouble handling money and paying bills, losing track of dates or locations, taking much longer to complete routine tasks, and poor judgment leading to unusual decisions. Mood and personality changes are also common, including increased anxiety, aggression, or a loss of motivation. These symptoms develop gradually, and the early stage, called mild cognitive impairment, can persist for years before progressing to full dementia.
Kidney Disease
Kidney disease is a top 10 cause of death worldwide, yet many people don’t realize they have it until significant damage has occurred. Your kidneys filter waste and excess fluid from your blood, and when they’re damaged, toxic byproducts accumulate throughout the body. This triggers a cascade of problems including inflammation, high blood pressure, and cardiovascular damage.
Diabetes and high blood pressure are the two most common causes of kidney disease. The connection runs both directions: kidney damage worsens blood pressure and blood sugar control, which in turn accelerates further kidney damage. This is why managing blood pressure and blood sugar early matters so much, not just for your heart, but for your kidneys as well.
Autoimmune Diseases
Autoimmune diseases occur when your immune system mistakenly attacks your own healthy tissues. There are more than 80 recognized types, including rheumatoid arthritis, lupus, multiple sclerosis, and type 1 diabetes. Women face up to four times the risk of developing an autoimmune disease compared to men. For certain conditions like lupus and Sjögren’s disease, the gender gap is even wider.
Rheumatoid arthritis tends to peak around age 55, while lupus often strikes women during their childbearing years. Symptoms vary widely depending on which tissues the immune system targets, but common threads include chronic fatigue, joint pain, inflammation, and symptoms that flare and recede unpredictably. Because autoimmune diseases can mimic other conditions and affect virtually any organ system, diagnosis often takes years.