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The most common risk factor for serious disease is old age. Heart disease, cancer, stroke, neurological conditions, diabetes — all increase radically with advancing years. And the older a person is, the more likely he or she is to have multiple chronic illnesses. Some scientists hope one day to treat all of them at once — by targeting aging itself. (Bakalar, 11/19)

Whenever I see a photo from the 1960s or 1970s, I am startled. It’s not the clothes. It’s not the hair. It’s the bodies. So many people were skinny. In 1976, 15 percent of American adults were obese. Now the it’s nearly 40 percent. No one really knows why bodies have changed so much. (Kolata, 11/19)

Vaccines are among the most ingenious of inventions, and among the most maddening. Some global killers, like smallpox and polio, have been totally or nearly eradicated by products made with methods dating back to Louis Pasteur. Others, like malaria and H.I.V., utterly frustrate scientists to this day, despite astonishing new weapons like gene-editing. (McNeil, 11/19)

Nothing humbles history’s great thinkers more quickly than reading their declarations on the causes of madness. Over the centuries, mental illness has been attributed to everything from a “badness of spirit” (Aristotle) and a “humoral imbalance” (Galen) to autoerotic fixation (Freud) and the weakness of the hierarchical state of the ego (Jung). The arrival of biological psychiatry, in the past few decades, was expected to clarify matters, by detailing how abnormalities in the brain gave rise to all variety of mental distress. But that goal hasn’t been achieved — nor is it likely to be, in this lifetime. (Carey, 11/19)

It’s a rare person in America who doesn’t know of someone with Alzheimer’s disease. The most common type of dementia, it afflicts about 44 million people worldwide, including 5.5 million in the United States. Experts predict those numbers could triple by 2050 as the older population increases. So why is there still no effective treatment for it, and no proven way to prevent or delay its effects? (Belluck, 11/19)

Cancer has an insidious talent for evading the natural defenses that should destroy it. What if we could find ways to help the immune system fight back? It has begun to happen. The growing field of immunotherapy is profoundly changing cancer treatment and has rescued many people with advanced malignancies that not long ago would have been a death sentence. (Grady, 11/19)