Heart disease has long been the leading cause of death. However, a new global study has shown — in higher income countries, at least — that cancer is now twice as likely to cause death as heart disease.

doctor tending for a patientShare on Pinterest
A recent study offers important insights into the leading causes of death worldwide.

In the United States, heart disease has traditionally topped the list as the leading cause of death for both men and women.

It is currently responsible for around 1 in 4 deaths. However, experts have been wondering when cancer will overtake it.

Now, a new study has found that cancer is fast becoming the leading cause of death in higher income countries.

This may seem like bad news, but the researchers behind the study — who investigated the occurrence of common conditions and causes of death in a wide spectrum of countries across the world — say that it is not necessarily so.

More specifically, they found that cancer now causes 55% of deaths among middle aged people in higher income countries, whereas heart disease causes just 23%.

The researchers, who have published their findings in The Lancet, say that this is due to improved efforts to prevent and treat heart disease in more prosperous countries.

"In some respects, this is a good news story," says co-lead study author Dr. Darryl Leong. "It suggests that efforts to treat blood pressure, cholesterol, and cardiovascular disease are meeting with some success."

Prevalence declining but more work needed

The SEER Cancer Statistics Review for 2018 noted a 26% drop in cancer-related deaths in the U.S. between 1991 and 2015.

Although this shows progress, there is still much work to be done, according to the National Cancer Institute. For example, the number of people smoking may have declined, but obesity is on the rise and the U.S. population is aging. All of these factors impact cancer statistics.

"Whether or not cancer rates are increasing is a complex question with no easy answer," Dr. Leong told Medical News Today. He heads the Cardio-Oncology Program at McMaster University and is affiliated with Hamilton Health Sciences in Canada.

"Different cancers have different patterns; cancer diagnosis rates depend in part on the use of screening tests in different populations; aging populations also affect the risk of developing cancer at a population level."

In their Prospective Urban Rural Epidemiology study, Dr. Leong and colleagues set out to get an up-to-date understanding of which conditions are the most significant threats to middle aged adults across the globe.

A study into current major health threats

The researchers conducted their study in 21 countries across five continents. The Population Health Research Institute of McMaster University and Hamilton Health Sciences headed up the project.

Over 9.5 years, the team followed 162,534 adults, ages 35–70, from:

  • high income Canada, Saudi Arabia, Sweden, and the United Arab Emirates
  • middle income Argentina, Brazil, Chile, China, Columbia, Iran, Malaysia, Palestine, the Philippines, Poland, Turkey, and South Africa
  • low income Bangladesh, India, Pakistan, Tanzania, and Zimbabwe

The researchers revealed that although heart disease is no longer the biggest killer in higher income countries, it remains the most common cause of death worldwide.

In middle income countries, heart disease was responsible for 41% of deaths, and in lower income countries, it was responsible for 43% of deaths. This is despite the risk factors that wealthier populations have.

Cancer ranked second most common, at 26%. However, although cancer was responsible for 55% of deaths in high income countries, this dropped to 30% in middle income countries and 15% in lower income countries.

The prediction is that as other countries start or continue to tackle the prevention and treatment of heart disease, cancer is likely to become the world's leading cause of death.

When the team took cancer out of the findings, overall mortality was highest in the low income countries (13.3%) and lowest in high income countries (3.4%), the former of which the researchers put down to reduced access to quality healthcare.

Clinical implications of the findings

This was the first time that researchers in this field have collected data in a global standardized study. It allowed them to compare "apples with apples."

"We collected information from participants in a standardized way, which allows us to compare different populations, whereas other studies might not be able to make these comparisons with as much confidence," Dr. Leong told us. "We felt that there were unique aspects to our data."

As for the clinical implications:

"With individuals surviving longer with cardiovascular disease, especially in high income countries, the development of other health issues, including cancer, will be a growing problem."

Dr. Darryl Leong

The answer, say the researchers, is to continue to prevent and treat heart disease while bumping up efforts to fight cancer.