New research reveals longevity gains slowing, life expectancy of 100 unlikely
University of Wisconsin-Madison
MADISON, Wis. – A new study co-authored by a University of Wisconsin-Madison professor finds that life expectancy gains made by high-income countries in the first half of the 20th century have slowed significantly, and that none of the generations born after 1939 will reach 100 years of age on average.
Published in the journal Proceedings of the National Academy of Sciences, the study by Héctor Pifarré i Arolas of the La Follette School of Public Affairs, José Andrade of the Max Planck Institute for Demographic Research, and Carlo Giovanni Camarda of the Institut national d'études démographiques analyzed life expectancy for 23 high-income and low-mortality countries using data from the Human Mortality Database and six different mortality forecasting methods.
“The unprecedented increase in life expectancy we achieved in the first half of the 20th century appears to be a phenomenon we are unlikely to achieve again in the foreseeable future,” according to Pifarré i Arolas. “In the absence of any major breakthroughs that significantly extend human life, life expectancy would still not match the rapid increases seen in the early 20th century even if adult survival improved twice as fast as we predict.”
From 1900 to 1938, life expectancy rose by about five and a half months with each new generation. The life expectancy for an individual born in a high-income country in 1900 was an average of 62 years. For someone born just 38 years later in similar conditions, life expectancy had jumped to 80 years on average.
For those born between 1939 and 2000, the increase slowed to roughly two and a half to three and a half months per generation, depending on the forecasting method. Mortality forecasting methods are statistical techniques that make informed predictions about future lifespans based on past and current mortality information. These models enabled the research team to estimate how life expectancy will develop under a variety of plausible future scenarios.
“We forecast that those born in 1980 will not live to be 100 on average, and none of the cohorts in our study will reach this milestone. This decline is largely due to the fact that past surges in longevity were driven by remarkable improvements in survival at very young ages,” according to corresponding author Andrade.
At the beginning of the 20th century, infant mortality fell rapidly due to medical advances and other improvements in quality of life for high-income countries. This contributed significantly to the rapid increase in life expectancy. However, infant and child mortality are now so low that the forecasted improvements in mortality in older age groups will not be enough to sustain the previous pace of longevity gains.
While mortality forecasts can never be certain as the future may unfold in unexpected ways – by way of pandemics, new medical treatments or other unforeseen societal changes – this study provides critical insight for governments looking to anticipate the needs of their healthcare systems, pension planning and social policies.
Although a population-level analysis, this research also has implications for individuals, as life expectancy influences personal decisions about saving, retirement and long-term planning. If life expectancy increases more slowly as this study shows is likely, both governments and individuals may need to recalibrate their expectations for the future.
Study can be seen here: https://www.pnas.org/doi/10.1073/pnas.2519179122
Journal
Proceedings of the National Academy of Sciences
Method of Research
Data/statistical analysis
Subject of Research
People
“Unhappiness hump” in aging may have disappeared worldwide
The change may be driven by declining mental health of younger people, not improvements in middle-age, per additional U.S. and U.K. data
PLOS
image:
Despair in the USA, 1993-2024.
view moreCredit: Blanchflower et al., 2025, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
A new survey-based study suggests that the “unhappiness hump”—a widely documented rise in worry, stress, and depression with age that peaks in midlife and then declines—may have disappeared, perhaps due to declining mental health among younger people. David Blanchflower of Dartmouth College, U.S., and colleagues present these findings in the open-access journal PLOS One on August 27, 2025.
Since 2008, a U-shaped trend in wellbeing with age, in which wellbeing tends to decline from childhood until around age 50 before rebounding in old age, has been observed in developed and developing countries worldwide. Data have also revealed a corresponding “ill-being” or unhappiness hump.
Recent data point to a worldwide decline in wellbeing among younger people, but most studies have not directly addressed potential implications for the unhappiness hump. To help clarify, Blanchflower and colleagues first analyzed data from U.S. and U.K. surveys that included questions about participants’ mental health. U.S. data included responses from more than 10 million adults surveyed by the Centers for Disease Control and Prevention between 1993 and 2024. U.K. data spanned 2009 through 2023 and were collected in the ongoing U.K. Household Longitudinal Study, which involves 40,000 households.
The analysis showed that, in the U.S. and the U.K., the ill-being hump has disappeared, such that ill-being / unhappiness now tends to decline over the course of a lifetime. Ill-being among people in their late 40s and older did not change significantly. Instead, the hump’s disappearance appears to be due to a decline in mental health among younger people.
Next, the researchers analyzed data on nearly 2 million people from 44 countries, including the U.S. and the U.K., from a mental health study called Global Minds. Covering the years 2020 through 2025, these data suggest the unhappiness hump has disappeared worldwide.
Reasons for the disappearance of the unhappiness hump are unclear. The authors suggest several possibilities, including long-term impacts of the Great Recession on job prospects for younger people, underfunded mental health care services, mental health challenges posed by the COVID-19 pandemic, and increased social media use. Further research is needed to determine whether any of these or other factors are at play.
The authors add: “Ours is the first paper to show that the decline in young people's mental health in recent years means that today, both in the United States and the United Kingdom, mental ill-being is highest among the young and declines with age. This is a huge change from the past when mental ill-being peaked in middle-age. The reasons for the change are disputed but our concern is that today there is a serious mental health crisis among the young that needs addressing.”
Despair by age, United States, 1993–2023.
Despair by age UK, UKHLS, 2009–2021.
Credit
Blanchflower et al., 2025, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
In your coverage, please use this URL to provide access to the freely available article in PLOS One: http://plos.io/4mMclpw
Citation: Blanchflower DG, Bryson A, Xu X (2025) The declining mental health of the young and the global disappearance of the unhappiness hump shape in age. PLoS One 20(8): e0327858. https://doi.org/10.1371/journal.pone.0327858
Author countries: U.K., U.S.
Funding: United Nations.
Journal
PLOS One
Method of Research
Survey
Subject of Research
Not applicable
Article Title
The declining mental health of the young and the global disappearance of the unhappiness hump shape in age
Article Publication Date
27-Aug-2025
Good sleep quality might be key for better mental wellbeing in young adults
Study also suggests eating fruit and vegetables and exercising are linked with strong benefits – and fruit and vegetable consumption might compensate for poor sleep
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Sleep, diet and physical activity are strong predictors of young adult wellbeing.
view moreCredit: Anthony Lewis, PLOS, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
A new study of young adults has strongly linked better sleep quality with better mental wellbeing, with fruit and vegetable consumption and physical activity also strongly associated with psychological wellbeing. Perhaps surprisingly, the findings also suggest that boosting fruit and vegetable intake could potentially help mitigate the effects on wellbeing of a poor night’s sleep. Dr. Jack Cooper, previously from the University of Otago, New Zealand, and colleagues present these findings in the open-access journal PLOS One on August 27, 2025.
Prior research has linked better health behaviors—actions that people can adjust in their lives—to better physical health. Evidence also suggests that health behaviors may be linked to mental wellbeing. However, research on this topic has been limited. For example, studies have typically focused only on mental illness, a separate measure from positive psychological wellbeing, and they typically neglect to consider how different health behaviors might interact to affect wellbeing.
To address these and other gaps, Cooper and colleagues analyzed relationships between three health behaviors—sleep quality, eating fruits and vegetables, and physical activity—and psychological wellbeing in adults aged 17 to 25. They used data from three studies: a survey study of 1,032 adults in New Zealand, the U.K., and the U.S.; a 13-day study of 818 New Zealand adults who were asked to keep a daily diary; and an 8-day diary study of 236 New Zealand adults who also wore Fitbits tracking physical activity.
Across all three studies, better sleep quality was most strongly associated with better mental wellbeing, with fruit and vegetable consumption coming in second. Both behaviors showed benefits even when comparing between different days for the same person – so eating more fruit and vegetables one day was associated with a real-time wellbeing boost. Physical activity – whether measured by FitBits or diaries, which aligned – was also linked to better wellbeing, but mostly when comparing between days for an individual rather than when comparing across individuals.
Links between each of the three behaviors and wellbeing appeared to be independent and additive - which might mean that the more of them you do, the bigger the wellbeing benefit. The only exception: above-average intake of fruits and vegetables appeared to mitigate the effects of a poor night’s sleep, and a good night’s sleep appeared to protect against lower fruit and vegetable intake.
This study used samples of young adults from three countries—the U.K., U.S., and New Zealand—and samples sizes were relatively homogeneous. Future research could address some of these limitations by including participants from additional countries and increasing the sample size to improve generalizability. Although this study could not prove a causative link between these behaviors and mental wellbeing, the authors hope that their findings could inform efforts to improve psychological wellbeing of young adults.
Lead author Dr. Jack Cooper adds: “Young adults don’t have to reach some objective benchmark of healthiness to see wellbeing improvement. Sleeping a little better, eating a little healthier, or exercising even for 10 minutes longer than you normally do was associated with improvements to how you feel that day.”
Senior author Professor Tamlin Conner, of the University of Otago Psychology Department, adds: “Understanding what lifestyle factors support wellbeing can help young adults not just ‘get by’ but thrive during this critical life stage.”
“Of these healthy habits, sleep quality stood out as the strongest and most consistent predictor of next-day wellbeing, but eating fruit and vegetables and being active also helped boost wellbeing".
“This age group faces unique pressures – such as leaving home, financial stress, educational pressures and social stressors – that can lower happiness. Understanding what lifestyle factors support wellbeing can help young adults not just ‘get by’ but thrive during this critical life stage.
In your coverage, please use this URL to provide access to the freely available article in PLOS One: http://plos.io/4fGrWEC
Citation: Cooper JR, Turner RS, Conner TS (2025) From surviving to thriving: How sleep, physical activity, and diet shape well-being in young adults. PLoS One 20(8): e0329689. https://doi.org/10.1371/journal.pone.0329689
Author countries: New Zealand
Funding: Portions of this research were funded by the New Zealand Health Research Council Emerging Researcher First Grant to TS Conner (Grant #12/709); https://www.hrc.govt.nz/ Funders played no role in the study design, data collection or analysis, decision to publish, or preparation of this manuscript.
Journal
PLOS One
Method of Research
Survey
Subject of Research
Not applicable
Article Title
From surviving to thriving: How sleep, physical activity, and diet shape well-being in young adults
Article Publication Date
27-Aug-2025
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