How the Leading Causes of Death Reshuffled Over 100 Years

At the turn of the twentieth century, death arrived early and often, and it usually came in the form of an infection. The three leading causes of death in 1900 were pneumonia and influenza, tuberculosis, and diarrhea and enteritis. Together with diphtheria, these communicable diseases accounted for about one-third of all deaths, and roughly forty percent of those infectious-disease deaths struck children under the age of five, according to the Centers for Disease Control and Prevention. A newborn in that era could expect to live only about 47 years, a number weighed down heavily by how many children never made it out of early childhood.

Tuberculosis alone claimed roughly 194 lives for every 100,000 people, a scale of loss that is almost hard to imagine today. It spread quietly through crowded housing and poor ventilation, and because there were no antibiotics, a diagnosis often meant a slow decline in a sanatorium far from home. This was the texture of the infectious era: illnesses that moved fast, hit the young hardest, and left families with little defense.

Now fast-forward to the present. The most recent complete national data comes from 2023, and the top of the list looks like a different world. Heart disease and cancer sit firmly in first and second place, followed by unintentional injuries, stroke, and a cluster of chronic conditions. The infectious diseases that once dominated have largely dropped away, replaced by the slow, age-related illnesses that tend to surface after many decades of life. The contrast is easiest to see when you place the two rankings next to each other.

Only a few names appear on both sides, and even those have shifted position and meaning. Heart disease, for instance, was already on the 1900 list, but it sat at number four and looked quite different in an era before we understood cholesterol, blood pressure, or smoking. The reshuffle was not a single event so much as a slow-motion turnover that played out across generations.

If you had to credit one thing for pushing infectious diseases down the list, it would not be a wonder drug. It would be clean water. Long before antibiotics arrived, cities began building sewage systems, treating drinking water, and improving food safety, and those unglamorous public works quietly saved enormous numbers of lives. The CDC's roundup of the twentieth century's great public health achievements credits sanitation, vaccination, and the control of infectious diseases among the milestones that most reshaped how and when Americans died.

Vaccines then took aim at specific killers. Diphtheria, which sat at number ten in 1900, became rare once childhood immunization spread. Later came the tools we most associate with fighting infection: penicillin moved into wide use in the 1940s, and streptomycin, isolated in 1943, finally gave doctors a way to treat tuberculosis directly. By the time these medicines arrived, though, the death rates from many infectious diseases had already been falling for decades thanks to better living conditions.

It helps to think of it as layers of defense stacking up over time. First came cleaner water, safer food, and less crowded housing. Then came vaccines that stopped certain diseases before they could start. Finally came antibiotics that could cure infections once they took hold. Each layer reinforced the last, and together they pulled the infectious diseases off the top of the list one by one. Researchers even have a name for this broad pattern, the epidemiologic transition, which simply describes how societies tend to move away from infectious, early-life deaths and toward chronic, later-life ones as living conditions improve.

Here is the part that surprises people. When infectious diseases retreated, the total risk of dying did not simply vanish. Instead, more people began living long enough to encounter a different set of conditions, the ones that tend to develop gradually over many years. Heart disease and cancer did not necessarily become more aggressive; they became more common largely because far more people now survived into the ages when those diseases appear.

By the late 1990s, heart disease and cancer together already accounted for well over half of all deaths in the United States, a striking reversal from the infectious-disease dominance of 1900. The everyday threats had shifted from the outside world of germs to the internal, cumulative wear of long life and modern habits. Writing in the New England Journal of Medicine, physicians reflecting on this century-long shift observed that optimism about future health "remained tempered by concern about the pathologies of civilization," a phrase that captures the trade-off neatly. We solved many of the problems of scarcity and infection, and in doing so we inherited the problems of abundance and age.

This is where understanding your own family history can feel more relevant than any single statistic, and it is one reason so much modern health writing focuses on chronic conditions rather than acute ones. For readers who want to go deeper on the single most common cause, our overview of the most changeable risk factors behind heart disease walks through the pieces researchers most often point to.

At first glance, heart disease sitting at number one for decades looks like a story of failure. It is actually closer to the opposite, and this is one of the most important and least understood parts of the whole reshuffle. Your risk of dying from heart disease at any given age has dropped enormously, even though it remains the leading cause of death overall.

Consider the trend. Age-adjusted heart disease death rates fell by roughly two-thirds between 1970 and 2022, dropping from about 761 deaths per 100,000 people to around 258, according to research published in the Journal of the American Heart Association. Coronary heart disease specifically fell even more steeply. Stroke followed a similar path, with age-standardized death rates among adults 35 and older falling from about 316 per 100,000 in 1968 to roughly 73 by 2015. Better blood pressure control, less smoking, and faster treatment of heart attacks and strokes all played a role.

So why is heart disease still number one? The answer comes down to how we count. It helps to know the difference between two kinds of numbers.

The long, slow reshuffle from infectious to chronic disease is the main storyline, but it was interrupted more than once by sudden shocks that briefly rearranged the list. These moments are worth remembering because they show that the transition was never a smooth, guaranteed march in one direction.

The most dramatic example came early. The 1918 influenza pandemic killed an estimated 675,000 Americans in about a year, a violent spike that struck young adults with unusual force and briefly overwhelmed every other cause of death. Decades later, another infection reordered the rankings for a specific group: by the mid-1990s, HIV and AIDS had become the leading cause of death for Americans aged 25 to 44, before new antiretroviral treatments drove those deaths down sharply. Both episodes were reminders that infectious disease had been pushed back, not eliminated.

More recently, two very different forces left their mark. Drug overdoses climbed almost every year for two decades, reaching a record of roughly 107,941 deaths in 2022, a rise the National Institute on Drug Abuse has tracked closely and one that helped push unintentional injuries up the list.

Then came COVID-19. Analyses by the National Institutes of Health found it was the third leading cause of death in both 2020 and 2021, behind only heart disease and cancer. By 2023 it had fallen to tenth. Few causes have ever climbed into the top three and back out again so quickly, a rise and fall compressed into just a few years.

It would be easy to assume the list has finally settled, with chronic diseases locked into place. The rankings are still shifting, though, just more subtly than before. The clearest sign is the quiet competition between the two heavyweights at the top.

Cancer has been gaining on heart disease for years. In 1999, heart disease caused more age-adjusted deaths than cancer in all fifty states. By 2016, cancer had become the leading cause of death in nineteen states, a change documented in a CDC analysis of state-level mortality. Heart disease still leads nationally, but the gap has narrowed enough that the number one spot is no longer a foregone conclusion.

This slow, state-by-state shift is a smaller reshuffle happening inside the larger one, and it varies from place to place in ways that mirror broader differences in how Americans live. If you enjoy seeing how health patterns break down geographically, our look at the most popular health trends by state explores some of that variation.

At the very top, though, the modern era has been relatively stable. For years now, heart disease, cancer, and unintentional injuries have consistently held the top three positions, with stroke and chronic lower respiratory diseases close behind. Compared with the wild turnover of the early twentieth century, today's list changes slowly, which is itself a sign of how thoroughly the chronic-disease era has taken hold.

Whenever you compare a list from 1900 with one from today, it is worth keeping a little humility about the details. The categories themselves have shifted over time, and understanding that makes the whole comparison more meaningful rather than less.

Official rankings come from the underlying cause listed on death certificates, which are coded using the International Classification of Diseases and tabulated by the National Center for Health Statistics. That coding system has been revised many times over the past century, and the way deaths are grouped has changed along with it. A category like "senility" on the 1900 list, for example, would be recorded very differently today, and conditions we now separate cleanly were once lumped together. Because of this, comparisons across a hundred years are best read as broad, directional patterns rather than exact, one-to-one matchups.

None of that changes the big picture, which is remarkably clear. The threats moved from infections that struck the young to chronic conditions that arrive with age, and that movement tracked one of the greatest gains in human longevity ever recorded. Seen that way, the reshuffling of the death rankings is not really a story about dying at all. It is a story about how many more years of living most of us can now expect, and about the clean water, vaccines, medicines, and steady public health work that made those years possible. For a forward-looking companion to this history, our guide to small daily changes that support healthy aging picks up where the numbers leave off.