Objective metrics that change the most as we age

Objective metrics that change the most as we age Brandon Ballinger May 23, 2026

Yeats wrote of an aged man as “a tattered coat upon a stick.” But for most of us, aging comes as small diminishments: the morning that takes a little longer to shake off, the flight of stairs you notice, the cold that lingers a week instead of three days, the run that used to feel easy. We register these shifts as fatigue or a busy season before we register them as time. The body is keeping score long before we are.

Each of these feelings has a number behind it.

The morning that takes longer to shake off lines up with kidney and liver filtration slowing down. Two glasses of wine hit differently at forty than at twenty, and as eGFR drops a few points per decade, the cleanup takes longer.

lines up with kidney and liver filtration slowing down. Two glasses of wine hit differently at forty than at twenty, and as eGFR drops a few points per decade, the cleanup takes longer. The flight of stairs you notice shows up as red blood cells slowly enlarging, each one a little less efficient at carrying oxygen.

shows up as red blood cells slowly enlarging, each one a little less efficient at carrying oxygen. The cold that lingers a week instead of three days is your lymphocyte counts thinning, the frontline cells that recognize and clear viruses.

is your lymphocyte counts thinning, the frontline cells that recognize and clear viruses. The run that used to feel easy tracks with hemoglobin A1c creeping upward, insulin sensitivity stiffening and muscles slower to pull glucose from the blood.

None of these metrics move more than a few percent in a year, but stacked across decades, they describe an aging body.

Which biomarkers rise and fall fastest with age? Which of these can be stopped, slowed, or reversed? In this post we’ll go through them.

The biomarkers that rise and fall the most with age.

... continue reading