“The second, published in 2013, is “The Hallmarks of Aging,” and enumerates nine changes which fit three criteria. First, they need to increase with age: if they don’t, how could they be causing aging? Second, accelerating a hallmark’s progress should accelerate aging, and, third, slowing one should improve it—these two criteria are an attempt to separate things which are merely associated with aging from things that are actually contributing to it. Finally, these hallmarks also come with suggested interventions which could slow or reverse their progression, thus slowing or reversing that aspect of aging, and hopefully putting the brakes on the process overall.”