Six systems, one prime decadeEach of these systems reaches its lifetime maximum sometime in the twenties or early thirties — then holds, or slowly slips. Tap one to see when it peaks and the single habit that best defends it.
Primary vs. secondary aging. Some decline is primary — biological, gradual, and universal. But much of what ages a body is secondary — driven by lifestyle and disease, and largely under your control. Early adulthood is where those choices start to compound.