Your Life Expectancy Might Be Shorter Than You Think

The Number You Think You Know Is Wrong

You probably assume your life expectancy is going up. Cleaner air, better medicine, fewer people dying of heart attacks in their 50s. The story we tell ourselves is that each generation outlives the last, and that trend will keep bending upward forever.

Kyle Foreman and his colleagues at the University of Washington looked at that assumption with 250 causes of death across 195 countries. They built a forecasting model that did not just project past trends forward. It tracked 79 independent drivers of health, from tobacco use to education levels to how many children women have before age 25. Then they asked: what happens if things get better? What happens if they get worse?

Their answer, published in The Lancet in 2018, is not what most people expect. Global life expectancy will probably rise by about 4.4 years for both men and women by 2040 (Foreman et al., 2018). That sounds good. But the range of possible outcomes is terrifying. Under the best case scenario, men could gain nearly 8 years. Under the worst case, they could lose ground. Women could see essentially no change at all (Foreman et al., 2018).

The future is not a smooth upward line. It is a fork in the road, and we are walking toward one branch without knowing which one.

How Do You Predict How People Die?

The researchers built their model using data from the Global Burden of Disease study, which tracks every death by cause in every country from 1990 to 2016. They did not just look at what killed people in the past and assume it would keep killing them at the same rate. Instead, they built a three part model.

First, they calculated how changes in risk factors like smoking, diet, and air pollution would shift death rates. Second, they modeled the underlying mortality rate for each cause as a function of three big structural drivers: income per person, average years of education, and the fertility rate among women under 25. Third, they used a statistical technique called an autoregressive integrated moving average model to capture whatever was left over, the unexplained changes that correlate with time itself.

They tested their model by feeding it data from 1990 to 2006 and asking it to forecast 2007 to 2016. Then they checked how close it got. When it performed well, they refitted it on the full 1990 to 2016 dataset and generated forecasts through 2040.

They also built two alternative scenarios. The "better health" scenario assumes every country achieves the 85th percentile of historical improvement across all risk factors. The "worse health" scenario assumes the 15th percentile. These are not fantasy scenarios. They are based on what countries have actually done in the past.

The Good News Is Conditional

Global life expectancy will probably hit 77.7 years for men and 83.3 years for women by 2040 (Foreman et al., 2018). That is real progress. Japan, Singapore, Spain, and Switzerland are projected to exceed 85 years for both sexes. Fifty nine countries, including China, will likely surpass 80 years.

But this is the reference forecast. It assumes current trends continue. It assumes no major policy failures. It assumes the world does not stumble.

The authors found that most independent drivers of health are forecast to improve by 2040. But 36 are forecast to worsen (Foreman et al., 2018). High body mass index, for example, will take a rising toll unless something changes. So will ambient particulate matter pollution. So will high blood pressure and high fasting plasma glucose.

These are not random bad luck. They are the consequences of how we eat, how we move, how we build our cities, and how we run our healthcare systems.

The Bad News Is Worse Than You Think

Under the worse health scenario, global life expectancy gains shrink to almost nothing. Men gain 0.4 years. Women gain 0.1 years. That is not a rounding error. That is a generation of progress erased.

The most dramatic example is HIV/AIDS. Under the worse health scenario, years of life lost to HIV/AIDS could increase by 120 percent globally between 2016 and 2040 (Foreman et al., 2018). That is nearly 118 million years of life that would not have been lost if the world stayed on its current trajectory. The authors are not predicting a new pandemic. They are warning that if countries lose momentum against HIV, if funding dries up, if prevention programs falter, the disease will come roaring back.

This is not hypothetical. We have seen it happen. When political will shifts, when budgets get cut, when attention moves elsewhere, infectious diseases do not politely wait their turn.

The Great Divide Is Not Closing

The countries that will suffer most under any scenario are the ones already suffering most. In 2040, the Central African Republic, Lesotho, Somalia, and Zimbabwe are projected to have life expectancies below 65 years (Foreman et al., 2018). That is 20 years less than Japan or Singapore. Twenty years.

In sub Saharan Africa, communicable, maternal, neonatal, and nutritional diseases will still account for 53.5 percent of years of life lost in 2040 (Foreman et al., 2018). That is not a failure of medicine. It is a failure of basic infrastructure. Unsafe water, household air pollution, child malnutrition. These are not diseases that require Nobel Prize winning research to solve. They require pipes, vaccines, and food.

The authors found that in most countries, the biggest gaps between the reference forecast and the better health scenario are driven by metabolic risks like high blood pressure and high blood sugar, and by population level risks like tobacco, obesity, and air pollution (Foreman et al., 2018). These are modifiable. They are not genetic destiny. But modifying them requires policy, not just individual willpower.

What This Actually Means

• ▸Your personal life expectancy depends more on where you live than on your genes. If you live in a country that invests in public health, you gain years. If you live in one that does not, you lose them. This is not a metaphor. It is a calculation based on 250 causes of death across 195 countries.

• ▸The biggest threats to your lifespan are not exotic diseases. They are high blood pressure, high blood sugar, tobacco, obesity, and air pollution. These are the risks where the gap between the reference forecast and the better health scenario is largest. They are also the risks that policy can actually change.

• ▸HIV/AIDS is not solved. The authors found that under the worse health scenario, years of life lost to HIV could more than double. The idea that we have beaten this disease is dangerous. We have not. We have just managed it, and management requires constant effort.

• ▸The future is not predetermined. The range between the better health and worse health scenarios is enormous. For men, it is a gain of 7.8 years versus a loss of 0.4 years. That range is not decided by technology or by fate. It is decided by what governments choose to fund, what industries choose to produce, and what individuals choose to demand.

• ▸The countries with the lowest life expectancies in 2040 will be the same countries that have the lowest life expectancies today. The gap is not closing on its own. Closing it requires deliberate action, not just hope.

The number you think you know about your future is wrong. Not because it is too optimistic or too pessimistic, but because it is not a number at all. It is a range. And the range is wide enough that we still have a choice.