The health problems that attract the world’s attention tend to be infectious diseases, like the respiratory illness COVID-19, which infected more than thirty million people around the world by September 2020. But some of the deadliest killers are no longer those that pass from person to person. A full 73 percent of the world’s deaths are the result of diseases such as cancer or diabetes that aren’t transmitted between people. These are called noncommunicable diseases (NCDs).

NCDs are a growing problem. In 1990, just three out of the top seven causes of death worldwide were noncommunicable. By 2015, that number had grown to six out of seven.

Global Prevalence of Noncommunicable Diseases

When you look at graphs showing all NCDs lumped together, the trend becomes apparent: rates of NCDs are on the rise everywhere. But when you begin to parse the data, other trends emerge, for example, how differently these diseases affect various communities.

To better understand the effects, let’s isolate the data on three of the deadliest NCDs: heart disease, dementia, and lung cancer. Each disease can show a different aspect of measuring, preventing, and treating NCDs.

Access to Health Care Matters

The most common type of heart disease is ischemic heart disease, which is related to problems with the arteries that bring blood to the heart. It’s the number one cause of death around the world and often caused by other conditions such as high blood pressure, high cholesterol, diabetes, and obesity. The disease can also result from lifestyle characteristics such as a lack of physical activity or smoking. It’s also shaped by something called the social determinants of health—factors like where people live, what they do for work, and how much they make. In the United States, systemic racism has influenced many of these factors, resulting in lower-quality health care for many people of color.

Health researchers use a measure called the Socio-Demographic Index (SDI) to evaluate a country’s level of development. Countries are given a grade that shows their level of development based on factors such as overall income and education. High SDI countries include the United States, Australia, and Russia; low SDI countries are mostly in Africa. A few indexes grade countries like SDI does, but SDI is unique in that it doesn’t incorporate overall health as a factor. This exclusion makes SDI a useful tool for health researchers because with health taken out of the picture, they can compare different countries and find out which factors help good health outcomes and which ones hinder them.

This is important to understand, for example, when looking at the mortality rates for heart disease. Separating the countries by their SDI rankings makes it clear that heart disease mortality rates are decreasing in high SDI countries but increasing in the lower SDI countries.

Deaths From Ischemic Heart Disease

So what does this mean? People in wealthy countries tend to have better access to health care, which makes dealing with chronic diseases easier, so deaths from chronic diseases are decreasing there. People in wealthy countries are also more likely to have access to preventive health care and thus be aware of risk factors such as high blood pressure or cholesterol, which can be managed before they can cause heart disease.

Middle SDI countries, such as China, and low-middle SDI countries, such as Nigeria, aren’t there yet. As these countries develop, their citizens become exposed to unhealthy lifestyle changes—think more sedentary office jobs or access to cheap fast-food options—that often accompany a country’s development. These lifestyle changes amplify the conditions that contribute to an increased risk of heart disease. And because access to health care tends to be more limited in these countries, the risk is magnified.

Age as a Challenge

Dementia is defined as the loss of or reduction in brain functions such as memory, decision-making, and even language. It occurs when healthy nerve cells in the brain deteriorate, lose connections with other brain cells, and die.

The average age for the onset of dementia is eighty years. Although dementia causes 2.5 million deaths each year, mortality isn’t the most useful way of measuring dementia’s effects. A more interesting way to understand the impact of something like dementia is to look at Years Lived With Disability (YLDs).

As life expectancies increase around the world, the rates of YLDs are also rising for dementia in all countries.

YLDs for Alzheimer’s Disease and Other Dementias

So what does this mean? Simply put, it means people with dementia are receiving care for longer periods of time than they used to.

Longer lifespans are generally a good thing. However, longer lifespans also mean more people with dementia who need long-term care, which is harder to access in low SDI countries that tend to have less-developed health infrastructure.

It’s also important to note that the reliability of data depends on how it was collected, and data collection can be affected by a variety of factors. For example, in high SDI countries, 25 to 50 percent of people with dementia go undiagnosed. In some middle and lower-middle SDI countries, the share of undiagnosed people is closer to 90 percent. This means that the rate of dementia in low SDI countries is possibly much higher than the data shows—and those living with undiagnosed dementia aren’t getting the care they need.

The Effect of Gender

Lung cancer is the growth of malignant tumors in the lungs. Besides skin cancer, lung cancer is the second most common form of cancer in the world. Although nonsmokers also get lung cancer, about 80 percent of lung cancer cases are caused by firsthand tobacco smoke. Keep this in mind while looking at lung cancer death rates in highly developed countries, which are generally going down for men but up for women.

Deaths From Tracheal, Bronchial, and Lung Cancer

So what does this mean? Health researchers are not sure exactly what is causing this discrepancy, but a leading hypothesis is that in many highly developed countries, women started smoking later than men and also quit later than men. Because lung cancer takes thirty to forty years to manifest, it makes sense that rates for men are decreasing while those for women are still rising. 

As trends such as vaping emerge, and as tobacco companies globalize and move into less developed countries, new cases of lung cancer could arise. While these cases will likely take decades to appear, it’s important to understand that today’s trends will affect how we measure diseases in the future. 

From Data to Your Day-to-Day Life

As lifespans extend and infectious diseases increasingly come under control, noncommunicable diseases pose a new kind of challenge to the progress made in global health. While NCDs are on the rise globally, data shows that not every disease affects everyone in the same way. People’s level of risk of heart disease, dementia, and lung cancer depends on who they are, where they live, and the choices they make.   

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