What are the deadliest diseases in the world?

By Liz Meszaros, MDLinx
Published October 3, 2019

Key Takeaways

As human beings, we are susceptible to hundreds, if not thousands, of diseases throughout our lives. Yet some diseases are far deadlier than others. As the world’s foremost international health organization, the World Health Organization (WHO) has ranked the 10 diseases with the highest global mortality rates.

Here they are, ranked according to the number of deaths each causes worldwide.

10. Cirrhosis. Accounting for 2.1% of all deaths worldwide, cirrhosis is caused by chronic damage to the liver from kidney disease, hepatitis, or chronic alcoholism. Risk factors include chronic alcohol abuse, nonalcoholic fatty liver disease, and chronic viral hepatitis. The complications of cirrhosis cause 1 million deaths per year throughout the world, and mortality rates have increased from 905,000 in 2000 to 1.2 million in 2015.

9. Tuberculosis. Tuberculosis accounted for 2.4% of deaths worldwide in 2015. But luckily, the prevalence of this disease—caused by Mycobacterium tuberculosis—is decreasing as is its mortality rate, from 2.3 million in 2000 to 1.3 million in 2015. Tuberculosis, however, remains one of the primary causes of death in people with HIV (35%). Risk factors for tuberculosis include low body weight, regular use of corticosteroid or immunosuppressive drugs, diabetes, HIV infection, and living in close proximity to those with tuberculosis. Preventive measures include the bacillus Calmette-Guerin (BCG) vaccine, usually given to children.

8. Diarrheal disease. Dehydration caused by diarrheal disease resulted in 1.4 million deaths in 2015, but its prevalence is decreasing, having dropped from 2.2 million deaths in 2000 to 1.4 million in 2015. Unfortunately, diarrheal disease is the second leading cause of death in children under the age of 5 years, and a primary cause of malnutrition in this age group. Worldwide, almost 1.7 billion cases of childhood diarrheal disease occur each year. Risk factors include living in areas with poor sanitary conditions, malnourishment, a weakened immune system, young age, and no access to clean water.

7. Alzheimer disease. This progressive neurologic disease accounted for 1.5 million deaths in 2015, and for 2.7% of all deaths worldwide. Its prevalence over the past 15 years (2000-2015) has increased from 1.2 million to 1.5 million. Risk factors include being female, over age 65 years, genetic predisposition, an unhealthy lifestyle, previous head trauma, and family history. In current studies, researchers have shown that diet may play a large role in reducing the risk of Alzheimer disease, especially one that is heart-healthy, low in saturated fats, and high in monounsaturated fats from fish, nuts, and olive oil.

6. Diabetes-related. The prevalence of diabetes-related death has increased from 1.0 million to 1.6 million from 2000 to 2015. In 2015, diabetes-related illnesses accounted 2.8% of all deaths throughout the world. Diabetes-related illnesses include cardiovascular disease, neuropathy, nephropathy, and retinopathy, along with a host of skin conditions and other complications.

5. Respiratory cancers. Cancers of the lungs, bronchus, larynx, and trachea comprise this group, and were responsible for 1.7 million deaths worldwide in 2015, totaling 3% of all deaths, and up from 1.2 million deaths in 2000. Pollution and smoking (both primary and secondary) are the primary causes of respiratory cancers. In fact, experts predict an 81% to 100% increase in respiratory cancers in developing countries due to these causes.

4. Chronic obstructive pulmonary disease (COPD). Chronic bronchitis and emphysema are the two primary forms of COPD, and there is some thought to adding asthma as well, although no consensus has been reached. COPD deaths accounted for 5.6% of all deaths worldwide, totaling 3.1 million in 2015. Risk factors include smoking, secondhand smoke, lung irritants, family history, and a history of respiratory infections as a child.

3. Lower respiratory infections. Flu, pneumonia, bronchitis, and tuberculosis are lower respiratory infections, and comprise 5.7% of deaths worldwide. But the number of deaths from lower respiratory infections decreased from 3.4 million in 2000 to 3.2 million in 2015. Viruses are the main cause of these infections, but bacteria are implicated as well. Risk factors include the flu, poor air quality, frequent exposure to respiratory irritants, smoking, asthma, HIV, immunocompromised status, and crowded childcare settings.

2. Stroke. Between 2000 and 2015, the mortality from stroke increased from 5.7 million to 6.2 million. Stroke was responsible for 6.2 million deaths in 2015, accounting for 11.1% of deaths worldwide. Stroke is also the leading cause of long-term disability. Diabetes, hypertension, hypercholesterolemia, smoking, and obesity are the leading causes of stroke. Risk factors include high blood pressure, family history of stroke, smoking (especially when combined with oral contraceptives), African American race, and female sex.

1. Coronary artery disease (CAD). The number one deadliest disease is CAD, responsible for 15.5% of all deaths worldwide. And mortality rates have been increasing, with a significant jump from 6 million deaths in 2000 to 8.8 million deaths in 2015. The good news is that mortality rates have gone down in the United States and many European countries, but the bad news is that deaths due to CAD are rising in many developing nations. Risk factors for CAD include hypertension, hypercholesterolemia, smoking, diabetes, overweight and obesity, and family history.

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