Living to 100 was once seen as extraordinary, but modern medicine has made longer lives more common, pushing scientists to ask why some people reach extreme old age. Researchers have explored whether fixed traits like blood type or early-life health markers influence longevity, looking beyond lifestyle alone to understand long-term biological patterns.

A large Swedish study offered valuable insight by tracking tens of thousands of people using national health records over several decades. Instead of relying on self-reports, scientists analyzed blood tests taken in midlife and compared those who later lived past 90 with those who did not. The goal was not prediction, but identifying subtle trends associated with long life.

The findings showed that people who lived longer often had slightly better metabolic health years earlier, especially more stable blood sugar levels. Chronic high glucose is known to accelerate aging through inflammation and vascular damage, so maintaining balance over time may lower the risk of heart disease, stroke, and cognitive decline. Cholesterol levels also mattered—not at extremes, but within moderate, stable ranges.

Kidney function and inflammation markers played a role as well, with long-lived individuals showing healthier readings earlier in life. Blood type itself had only a minor influence, reinforcing the idea that longevity is not driven by a single factor. Instead, it appears to emerge from many small advantages accumulating over a lifetime—shaped by genetics, habits, environment, and sustained physiological balance.