The number of people reaching 100 is rising faster than ever. According to the United Nations report World Population Prospects (2024 revision), the global population of centenarians has roughly doubled every decade since 1950 — and is projected to grow fivefold between 2022 and 2050.

Living that long isn’t the result of a single secret. Longevity is shaped by a complex mix of genetics, lifestyle, environment, and even social connections. While researchers still don’t fully understand why some people reach exceptional ages, studying these individuals offers valuable clues about how both lifespan and healthspan might be extended.

Insights From a Swedish Longevity Study

Centenarians were once so rare that their birthdays made local headlines. Even today, scientists remain fascinated by what separates those who live a century from those who don’t.

A major study from Sweden followed 44,637 people from Stockholm County, tracking their health for up to 35 years. Among them, 1,224 eventually reached age 100 — about 85% were women, reflecting the well-known trend that women tend to outlive men.

Rather than focusing only on age, researchers analyzed routine blood tests taken decades earlier to see whether certain markers could predict long-term survival.

The Biomarkers Linked to Longer Life

The researchers examined 12 common blood markers tied to metabolism, nutrition, inflammation, liver health, and kidney function. One pattern stood out clearly:

👉 Extremes — either too high or too low — were linked to lower chances of reaching 100.

People who became centenarians generally showed:

• Lower glucose levels

• Healthy kidney markers such as creatinine

• Reduced uric acid, often associated with inflammation

These subtle advantages in midlife appeared to influence survival decades later.

Cholesterol and Iron: Why Balance Matters

Interestingly, the findings challenged some common assumptions.

• Slightly higher total cholesterol was associated with a modest increase in the likelihood of living to 100 — a pattern seen in previous research on very elderly populations.

• Very low iron levels were linked to poorer survival odds.

The takeaway wasn’t that “higher is better,” but that stable, moderate ranges seem to support long-term health.

Kidney function also emerged as a quiet but powerful predictor, helping the body regulate blood pressure, filter toxins, and process medications over many years. Lower levels of chronic inflammation appeared to further protect organs as people aged.

The Genetic Piece of the Puzzle

Genes clearly contribute to longevity, though they don’t tell the whole story. Variants such as FOXO3A — linked to stress resistance and insulin signaling — have been repeatedly associated with longer lifespans.

Blood type may play a minor role by slightly influencing disease risk or clotting patterns, but researchers emphasize that it does not determine whether someone will live to 100. Longevity is far more layered than any single inherited trait.

What This Means for Everyday Life

You don’t need flawless lab numbers to live longer — and chasing perfection isn’t the goal. The strongest message from decades of data is surprisingly simple:

Consistency beats extremes.

Small habits practiced over many years quietly shift the odds in your favor:

• Keep blood sugar steady with balanced meals

• Stay hydrated and support liver and kidney health

• Limit alcohol and ultra-processed foods

• Move regularly

• Prioritize sleep

• Manage stress

These actions may seem ordinary, but their effects compound over time.

Beyond the Data

One of the most remarkable aspects of the Swedish research is its duration. Instead of capturing a moment in time, it revealed how midlife health can echo across decades.

No single factor guarantees a century of life. Genetics, biomarkers, daily choices, and even a measure of luck all intertwine.

Even attention-grabbing details like blood type are just small pieces of a much larger picture.

The Real Lesson From Centenarians

The people who reached 100 weren’t perfect — their diets, routines, and genetics all varied. What they shared was a foundation of generally balanced health that accumulated quietly over the years.

Longevity isn’t about dramatic transformations. It’s about sustainable choices repeated day after day.

No one can promise a hundred candles on your cake. But caring for your body, avoiding extremes, and building steady habits can influence your future more than you might imagine.

Because in the end, a long life is rarely built on one big decision — it’s shaped by thousands of small ones.