Onset of millennial climate variability with the intensification of Northern Hemisphere glaciation - Science | AAAS

Changes in our genes affect health risks from heart disease to cancer, but how those genes are turned on and off is just as crucial to health. What's more, almost all genes occur as two copies—one from each parent—that aren't necessarily turned on and off in sync. When that differential gene regulation goes awry, it can cause serious health problems.

In mid-September 2026, Hurricane Polo began as a tropical disturbance off the Pacific coast of Mexico. By September 20, it was organized enough to qualify as a tropical depression, and by the next day it was a tropical storm. From there, Polo launched into a period of rapid intensification that left meteorologists searching for adjectives strong enough to convey what was happening. Some described the storm's rate of intensification and strength as "jaw-dropping," others as "astonishing," and others as "absolute insanity. "

On September 9th, Apple announced it was revamping its Apple Watch Health Sensing System, rolling out a Readiness score (0 to 10), and increasing the frequency of heart rate variability (HRV) outputs 24-fold. This can be viewed as upping its competition with various other consumer wearable sensors. These “readiness scores” as a composite of multiple metrics, with heart rate variability (HRV) being front and center for most. The majority of Americans are now using wearable sensors, which equates to well over 100 million adults. HRV and Readiness scores are increasingly being marketed as a measurement of autonomic nervous system health, a digital marker for future disease, a clock for biological age, and a holistic metric to promote healthspan and even longevity. (Apple also introduced a new longevity tab and “Health Age”.) None of this has been proven. In this edition of Ground Truths I am going to review what we know about heart rate variability and readiness scores. HRV is the variation in normal heart cycle timing.