Why millennials may not reach 100: Study shows life expectancy slowing

A new study shows life expectancy gains are slowing, with millennials and Gen Z unlikely to reach 100 on average, challenging long-held assumptions about human longevity

Do you dream of living to 100? For decades, that seemed within reach, as life expectancy kept rising with every generation—thanks to vaccines, improved healthcare, and better living conditions. But new research warns this upward trend is now slowing, and future generations may not enjoy the same leap in longevity.

 

A recent study titled “Cohort mortality forecasts indicate signs of deceleration in life expectancy gains”, published in Proceedings of the National Academy of Sciences (PNAS), finds that people born between 1939 and 2000 in high-income countries are unlikely to reach the century mark on average.

 

Researchers from the Max Planck Institute, INED, and the University of Wisconsin-Madison found that life expectancy improvements are slowing significantly in 23 high-income countries.

 

 

What did the new study reveal?

 

The study analysed whether those born between 1939 and 2000 would see the same longevity gains as previous generations. Using six different forecasting models, the researchers found a sharp slowdown—life expectancy gains were 37 to 52 per cent lower than those seen in the early 20th century.

 

So, while people born in 1980 were once expected to live to 100, updated forecasts show they are likely to fall short. 

Why are lifespans no longer rising as fast?

 

In the early 1900s, life expectancy rose rapidly due to antibiotics, vaccines, better nutrition, sanitation, and reduced infant mortality. Those “easy wins” contributed massively to longevity improvements.

 

Now, with survival already high in younger age groups, there’s less room for drastic gains. The study found over 70 per cent of the slowdown came from reduced improvements in survival under age 20.

 

Can science still reverse the slowdown?

 

Medical breakthroughs can always change the picture—whether it’s anti-ageing therapies or better chronic disease treatment. But even under optimistic projections, where survival rates double in the future, life expectancy gains still don’t match the leaps seen before 1938.

 

The takeaway: medicine can enhance quality of life, but may not easily push average lifespans to 100. 

Why this matters to society

 

Life expectancy influences retirement age, healthcare budgets, and pension planning. Slower gains could mean more years of chronic illness without the offset of reaching extreme old age.

 

For governments, this raises pressing questions around healthcare costs, an ageing workforce, and future social policies.

 

Will today’s kids become centenarians?

 

Not likely. A separate study in Nature Ageing estimates just 5.1 per cent of girls and 1.8 per cent of boys born today will reach 100. The reasons? Rising childhood obesity, poor diets, screen addiction, and inactivity are creating serious long-term health risks.

 

Do lifestyle choices still matter?

 

Absolutely. While genetics set limits, habits shape outcomes. Children who eat well, exercise, sleep enough, and maintain strong social connections are more likely to live longer and healthier lives.

 

Parents can help by encouraging balanced meals, outdoor play, emotional support, and regular check-ups.

 

Living longer or living better?

 

Experts say the focus should shift from merely reaching 100 to adding healthy years. A life with fewer years of disability—physical, mental, or emotional—may matter more than hitting a milestone.

 

As the PNAS study shows, the dream of universal 100-year lifespans may be fading. But with smart choices, the goal can shift: not just more years, but better ones. 

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This content is for informational purposes only and is not a substitute for professional medical advice.