The 2024 Revision of World Population Prospects reports that the number of centenarians—people who live to 100 or older—has nearly doubled every decade worldwide since 1950. Researchers also expect that number to increase fivefold between 2022 and 2050.
A long lifespan is shaped by a complicated mix of many factors, and scientists still do not fully understand all of them.
Although genetics play an important role, longevity is also influenced by lifestyle, environment, and social connections. Why some individuals reach 100 while others do not remains largely uncertain, which is why the topic continues to fascinate researchers. Understanding what contributes to both lifespan and health span in these extraordinary individuals may eventually help extend healthy aging for future generations.
Research like this helps scientists better understand how aging develops throughout life while also revealing clues about what supports exceptional longevity. In the end, discovering what strengthens both lifespan and long-term health in centenarians may guide future approaches to healthier aging.
REACHING 100? INSIGHTS FROM A GROUNDBREAKING SWEDISH STUDY
Centenarians were once so rare that their birthdays became newspaper headlines and community celebrations. Even today, living to 100 remains unusual, and scientists have long searched for the reasons some people outlive others. Is it genetics? Lifestyle? Luck? Or all three combined?
A major study from Sweden offers part of the answer.
Researchers gained access to decades of medical records involving tens of thousands of individuals and wanted to know whether ordinary blood tests taken during midlife could predict who might eventually live to 100.
DECADES OF TRACKING
The research followed 44,637 people from Stockholm County. All participants, born between 1893 and 1920, were between 64 and 99 years old when routine blood tests were performed between 1985 and 1996. Researchers then tracked these individuals for up to 35 years using national records for health, residency, and mortality.
Out of all participants, 1,224 eventually reached 100 years old, and approximately 85 percent were women. That result was not especially surprising since women generally outlive men. However, researchers were interested in more than simply counting birthdays. They wanted to know whether blood markers measured decades earlier could reveal hidden clues about longevity.
And the results suggested they could.
THE MARKERS THAT MATTER
Researchers analyzed 12 common blood markers. These included glucose and total cholesterol for metabolic health, creatinine for kidney function, liver enzymes such as gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), and lactate dehydrogenase (LD), iron-related markers, uric acid as a possible sign of inflammation, and albumin, which reflects nutrition and protein intake.
The findings clearly showed that extreme values—either too high or too low—were linked to a lower likelihood of reaching 100.
As researcher Karin Modig explained in a Live Science interview:
“We found that, on the whole, those who made it to their hundredth birthday tended to have lower levels of glucose, creatinine, and uric acid from their 60s onwards. For example, very few of the centenarians had a glucose level above 6.5 earlier in life, or a creatinine level above 125.”
The study suggests that even small advantages maintained over decades may gradually improve the odds of exceptional longevity.
CHOLESTEROL AND IRON: MODERATION MATTERS
Many medical guidelines focus heavily on lowering cholesterol, but the Swedish research revealed a more nuanced picture. Slightly higher total cholesterol levels were actually connected to a modest increase in the chances of reaching age 100. Researchers noted that earlier studies had occasionally found elevated cholesterol to be beneficial in some elderly populations.
Iron levels showed a similar trend. Extremely low iron was associated with lower odds of living to 100.
The message appears clear: extremes are rarely ideal. Stability and moderation matter most.
Kidney health also played a major role. People who lived the longest generally showed healthier kidney function during midlife, helping their bodies manage toxins, medications, and blood pressure over many years. Liver function also mattered, though less dramatically. Researchers consistently found lower inflammation levels among centenarians and supercentenarians, suggesting reduced inflammation may help organs and tissues remain resilient with age.
THE ROLE OF GENETICS
Genes clearly contribute to longevity as well.
Additional studies reviewed alongside the Swedish research highlighted genetic variations such as FOXO3A, linked to stress resistance and insulin signaling; APOE and PON1, which influence cardiovascular health and fat metabolism; and TP53 and P21, which help regulate cell cycles and protect against age-related damage.
Blood type, although determined at birth, may only play a small role. Certain blood types could slightly influence disease risk or blood clotting, but they do not decide whether someone lives to 100. Longevity is far more complicated than one gene or one blood type alone.
Modig explained:
“The study does not allow conclusions about which lifestyle factors or genes are responsible for the biomarker values. However, it is reasonable to think that factors such as nutrition and alcohol intake play a role. Keeping track of your kidney and liver values, as well as glucose and uric acid as you get older, is probably not a bad idea.”
She also added:
“That said, chance probably plays a role at some point in reaching an exceptional age. But the fact that differences in biomarkers could be observed a long time before death suggests that genes and lifestyle may also play a role.”
WHAT THIS MEANS FOR YOU
So what should people take away from all of this?
The simple answer is that perfect lab results are not necessary for a long life. There is no need to obsess over every number or chase extremes. What matters most is maintaining balanced habits consistently over time.
Blood sugar is one example. Avoiding constant spikes from sugary foods and drinks can help maintain stability. Meals rich in protein, fiber, and healthy fats may support better balance.
The kidneys and liver also work constantly behind the scenes, so staying hydrated, limiting alcohol, using medications carefully, and eating nutrient-rich foods can help protect them over time.
Cholesterol and iron appear similar: extremes may be harmful, while moderate levels seem more supportive of longevity.
Inflammation may also be reduced through regular movement, quality sleep, stress management, and diets rich in fruits and vegetables.
The larger lesson is that small habits accumulate quietly across decades. A healthier meal, an extra walk, or one more night of restful sleep may slowly shift the odds in your favor over time.
Longevity is not about perfection.
It is about consistency.
BEYOND THE NUMBERS
One of the most remarkable parts of this study is its length. This was not a brief survey or a single snapshot in time. Researchers followed people for decades, showing how factors during midlife—such as blood sugar, kidney health, and inflammation—may influence outcomes many years later.
Longevity rarely depends on a single factor. Genetics, biomarkers, lifestyle habits, and even luck all interact together. Nothing guarantees someone will live to 100, but maintaining balanced habits throughout life appears to improve the chances.
Even blood type, while often highlighted in headlines, remains only one small piece of a much larger puzzle. The broader picture points toward consistency: stable health, balanced choices, and long-term care for the body year after year.
THE HUMAN LESSON
Ultimately, this study is not about becoming obsessed with medical tests.
The centenarians involved were not perfect people. Their diets, lifestyles, and genetics all varied. What connected them was decades of generally balanced health and the quiet benefits that build slowly over time.
“It’s about living well every day, letting your habits compound over time,” Modig says.
Balanced meals, regular walks, proper sleep, and small efforts to reduce stress all add up.
No one can promise you will live to 100. But paying attention to your health, avoiding extremes, and sticking with sustainable habits truly can make a difference.
The small decisions you make today may shape your future in ways you never expected.
