From Junkfood Science

I suppose we all remember the big story about how rhesus monkeys kept on a highly-restrictive diet lived longer than those who were allowed to nosh at will. Turns out that this is only true if you, well, ignore the monkeys that died.

The lower mortality claimed among the monkeys on the calorie restricted diet were achieved only after eliminating 37% of the monkey deaths. They defined mortality as “age-associated deaths” and eliminated any cause of death they didn’t believe was associated with aging. As the supplemental data explains, 16 deaths from “non-age-associated causes were censored and their age of death used as the time variable in the regression.”

. . . The non-aging-related causes of death included monkeys who died while taking blood samples under anesthesia, from injuries or from infections, such as gastritis and endometriosis. These causes may not be aging-related as defined by the researchers, but they could realistically be adverse effects of prolonged calorie restrictions on the animals’ health, their immune system, ability to handle stress, physical agility, cognition or behavior.

As we know, the most important endpoint in medical interventions is all-cause mortality. Selectively looking at only one cause of death, while ignoring that more patients died from something else, is not evidence to support the efficacy of a treatment. “The treatment worked, but the patient died” is not good medicine that considers the whole patient."

More over on the Junkfood Science blog.