For most of human history, living to 100 was something almost mythical — a rare milestone reached only by the exceptionally fortunate or unusually robust. But with advances in medicine, sanitation, nutrition, and overall living conditions, people crossing the century mark are no longer viewed as extraordinary. In fact, they’re becoming one of the fastest-expanding age groups in numerous nations. Even so, the question remains: why do some individuals survive well into extreme old age while others do not?
A team of Swedish scientists decided to investigate one piece of that puzzle by examining decades of health information. They didn’t look for magic longevity regimens, exotic superfoods, or secret anti-aging strategies. Instead, they turned to something completely ordinary: routine blood tests collected many years — even decades — before anyone reached advanced old age.
Their guiding question was simple but ambitious: can everyday blood markers help predict who has a better chance of living past 100?
To find out, the researchers analyzed data from tens of thousands of people, linking blood test results to long-term health records through Sweden’s remarkably detailed national registries. This wasn’t guesswork or anecdotal observation — it was solid, longitudinal data followed for as long as 35 years. While the findings don’t offer a guaranteed path to exceptional longevity, they provide fascinating insights into survival, resilience, and the underlying biology of aging.
The study used the AMORIS cohort, a huge clinical database built from routine lab tests taken in Stockholm County. From a pool of over 800,000 individuals, researchers narrowed their focus to 44,636 people born between 1893 and 1920 who had blood work done between 1985 and 1996. This meant everyone was roughly the same age when tested, making comparisons more consistent and fair.
Participants were followed until either death or the end of 2020. Out of the entire group, 1,224 reached the age of 100. About 85 percent of these centenarians were women, reflecting the worldwide trend that females generally live longer. Thanks to Sweden’s national data systems, scientists could accurately connect blood test values with hospital admissions, diagnoses, death certificates, and long-term health outcomes. Standard statistical methods — logistic regression, descriptive comparisons, and clustering analyses — were used to identify which biomarkers aligned with exceptional longevity.
The researchers examined 12 common blood markers: glucose, total cholesterol, creatinine, albumin, uric acid, iron, total iron-binding capacity, and several liver enzymes (AST, GGT, ALP, LD). These are all routine laboratory results a primary-care doctor might check during a standard physical exam.
Some people initially misinterpreted the cholesterol findings, so the study authors clarified them. Extremely low cholesterol — specifically in the lowest fifth of results — was associated with lower odds of reaching age 100. High cholesterol, however, did not significantly raise or reduce the likelihood. Essentially, very low cholesterol may signal frailty or underlying illness, while moderate or somewhat elevated cholesterol is not necessarily harmful for achieving extreme age.
The main theme was consistent: extremes, whether high or low, rarely predict long life. Stability and moderation appeared far more favorable.
This pattern extended to multiple markers. Low iron levels were tied to a reduced chance of becoming a centenarian, while very high iron-binding capacity (a sign the body is struggling to access iron) also pointed to lower odds. This again underscored the “danger zones” on both ends of the spectrum.
High glucose readings were strongly connected to decreased chances of reaching 100, aligning with decades of research on the dangers of elevated blood sugar. Chronic hyperglycemia harms nerves, blood vessels, and organs, raising the risk of heart disease, stroke, and early death.
For glucose, the lesson was clear: consistently high levels significantly reduce the likelihood of exceptional longevity. The researchers didn’t diagnose diabetes in participants; instead, they grouped individuals into quintiles and tracked outcomes. Still, the biological logic matched existing medical guidance — controlling blood sugar is essential for long-term health.
Kidney and liver function markers presented their own stories. Elevated creatinine — a sign of reduced kidney filtration — was linked to lower odds of living to 100. Since kidney function naturally declines with age, persistently high creatinine is a red flag and should never be dismissed.
Several liver enzymes revealed similar trends. Individuals with high gamma-glutamyl transferase, alkaline phosphatase, or lactate dehydrogenase had a lower chance of reaching the century mark. These enzymes can rise due to alcohol use, liver damage, medication effects, or broader metabolic stress. The implication is simple: when the liver struggles over long periods, longevity becomes less likely.
Aspartate aminotransferase (AST) showed a U-shaped relationship — both very high and very low levels were linked with reduced odds of hitting 100. This suggests that not only liver distress but also malnutrition, frailty, or muscle loss may influence AST levels and long-term survival.
Uric acid, known for its role in gout and metabolic dysfunction, produced one of the most striking dose-response curves. Those in the highest uric acid group had the lowest chance of reaching 100, while those in the lowest group had nearly double the likelihood. The researchers pointed out that high uric acid often accompanies chronic inflammation and metabolic imbalance — two major enemies of longevity.
In a subset of participants, C-reactive protein (CRP), a major marker of inflammation, was also examined. Lower CRP levels were tied to better odds of exceptional longevity, matching extensive research linking low inflammation to healthier aging. Because CRP data wasn’t available for everyone, the finding is suggestive rather than definitive.
Across all markers, the same principle emerged again and again: long life isn’t generally associated with extremely “perfect” numbers but with steady, moderate ones. Both ends of the spectrum — too high or too low — consistently corresponded with reduced chances of reaching 100. The middle ranges were where resilience tended to live.
Glucose that stays controlled.
Cholesterol that sits in a healthy but not overly suppressed range.
Liver enzymes that remain steady rather than spiking.
Kidney values that don’t creep upward.
Uric acid kept from rising.
Iron levels that remain balanced — neither deficient nor excessive.
These patterns match what physicians observe every day, but the long follow-up period in this study adds weight and clarity.
This research does not claim that a single blood test can determine destiny. Longevity depends on a mixture of genetics, lifestyle choices, environment, stress levels, social support, diet, physical activity, medical care, and chance. But these biomarkers offer hints about the body’s internal state — signals that show which systems are thriving, which are struggling, and which are quietly setting the stage for either resilience or decline.
Ultimately, the Swedish study’s message is straightforward and reassuring. There are no magical lab values. No miracle targets. Instead, longevity appears to favor bodies that avoid extremes — bodies that maintain metabolic balance, keep inflammation low, and preserve organ health over many years.
A century-long life isn’t built overnight. But part of its foundation can be glimpsed in the most ordinary of places — routine lab work.
And for many people, that means the numbers worth watching are the ones we often overlook.