Health concerns are conditions, behaviors, and environmental factors that threaten physical or mental well-being at a population level. The biggest ones right now include heart disease, cancer, diabetes, mental health disorders, obesity, antibiotic resistance, and the growing burden of dementia in aging populations. In the United States alone, more than 194 million adults (76.4% of the population) have at least one chronic health condition.
Heart Disease and Stroke
Heart disease is the single largest killer worldwide, responsible for 13% of all deaths globally. In 2021, 9.1 million people died from blocked or narrowed heart arteries, an increase of 2.7 million deaths compared to the year 2000. Stroke ranks as the third leading cause of death, accounting for roughly 10% of total deaths worldwide.
In the U.S., about 34.5% of adults have high blood pressure, which is the primary driver of both heart attacks and strokes. High cholesterol and obesity compound the risk. These aren’t just concerns for older adults. Blood pressure tends to creep up starting in your 30s, and the damage to arteries accumulates silently over years before symptoms appear.
Cancer
Lung cancer has seen a sharp rise in deaths globally, climbing from 1.2 million in 2000 to 1.9 million in 2021. It now ranks as the sixth leading cause of death worldwide. Colorectal cancer is another major concern, and screening recommendations have shifted to reflect that: the recommended starting age for colorectal screening dropped from 50 to 45 in recent years, with colonoscopy every 10 years as one standard approach.
Early detection remains the most effective tool for improving cancer outcomes. Breast, cervical, and lung cancers all have established screening protocols that catch disease at stages when treatment is far more effective.
Diabetes and Obesity
Diabetes deaths have surged 95% since 2000, making it one of the fastest-growing causes of death in the world. In the U.S., 12.1% of adults now have diabetes. The condition damages blood vessels, nerves, kidneys, and eyes over time, and it dramatically increases the risk of heart disease and stroke.
Obesity is a central driver. Globally, 2.5 billion adults were overweight in 2022, with over 890 million classified as obese. That’s 43% of all adults, up from 25% in 1990. The numbers vary by region: 67% of adults in the Americas are overweight, compared to 31% in Southeast Asia and Africa. Excess weight doesn’t just raise your risk for diabetes. It contributes to joint problems, sleep disorders, certain cancers, and heart disease, making it one of the most far-reaching health concerns of the 21st century.
Mental Health
Anxiety and depression together now account for 9.1% of all disease burden worldwide. In 2021, roughly 359 million people were living with an anxiety disorder and 332 million with depression. Combined, these two conditions make up 63.1% of all mental health disorders globally.
The trend is moving in the wrong direction. Between 1990 and 2021, the burden of anxiety disorders increased by 18.2%, and depressive disorders by 13.4%. Prevalence rises with age, but the 10 to 24 age group is seeing particularly notable increases. Women are affected at higher rates than men. By 2040, projections suggest anxiety cases will surpass 515 million and depression will exceed 466 million globally.
Dementia and Alzheimer’s Disease
Alzheimer’s disease and other forms of dementia ranked as the seventh leading cause of death worldwide in 2021, killing 1.8 million people. In the United States, an estimated 7.2 million Americans age 65 and older are living with Alzheimer’s dementia today. That number could reach 13.8 million by 2060 without major treatment breakthroughs.
The financial toll is staggering. Total payments for dementia care in the U.S. are estimated at $384 billion in 2025, and that figure is projected to approach $1 trillion annually by 2050. This doesn’t include the value of unpaid caregiving provided by family members, which adds an enormous hidden cost in lost income and caregiver burnout.
Antibiotic Resistance
When bacteria evolve to survive the drugs designed to kill them, infections that were once routine become life-threatening. In 2021, an estimated 1.14 million deaths were directly caused by antibiotic-resistant bacteria, and 4.71 million deaths were associated with resistant infections. By 2050, resistant bacteria are projected to directly kill 1.91 million people per year, with 8.22 million deaths linked to resistance overall.
This affects everyone, not just people with unusual infections. Resistant bacteria make routine surgeries riskier, complicate treatment for urinary tract infections, and reduce options for pneumonia and wound care. Overuse of antibiotics in both human medicine and agriculture continues to accelerate the problem.
Respiratory Diseases
Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide, responsible for about 5% of all deaths. In the U.S., 6.2% of adults have COPD, and another 9.8% have current asthma. Lower respiratory infections like pneumonia remain the deadliest communicable disease after COVID-19, killing 2.5 million people in 2021.
Kidney disease, often overlooked, has climbed from the 19th leading cause of death globally in 2000 to the 9th, with deaths increasing 95% over that period. It’s closely tied to diabetes and high blood pressure, meaning the rise in those conditions feeds directly into rising kidney failure rates.
Climate Change and Infectious Disease
Rising global temperatures are expanding the geographic range of disease-carrying mosquitoes, ticks, and rodents. Malaria-carrying mosquitoes are now found at higher altitudes and latitudes than in previous decades. Heat waves directly increase deaths from cardiovascular and respiratory illness, particularly among older adults and outdoor workers. Extreme weather events also worsen waterborne diseases like cholera and contribute to food insecurity and malnutrition.
Projections for the late 21st century point to increased mortality from thermal stress, a broader spread of vector-borne diseases, and more frequent outbreaks of diarrheal illness in vulnerable regions.
Youth-Specific Health Risks
For adolescents aged 10 to 19, the leading causes of death look very different from adults. Injuries, particularly road traffic accidents and drowning, top the list. In 2021, over 100,000 adolescents died in traffic accidents, and more than 40,000 drowned (three-quarters of them boys). Interpersonal violence and self-harm are also among the leading causes of death in this age group. Mental health disorders are rising sharply among young people, with the 10 to 24 age range showing some of the steepest increases in anxiety and depression prevalence.
Pandemic Preparedness
COVID-19 caused an estimated 8.8 million deaths in 2021 alone, pushing it to the second leading cause of death globally that year. Beyond the death toll, the pandemic caused trillions of dollars in economic losses and lasting disruptions to education, social connections, and mental health. Despite this experience, global health experts warn that the world remains highly vulnerable to future pandemics due to persistent inequities in health infrastructure, public mistrust, and chronic underinvestment in preparedness systems. Low- and middle-income countries bear the greatest risk, both from emerging infections and from the economic aftershocks of outbreak response.