N=133,000 over 40 year time period
Observational study so limitations may apply but the findings do hold after adjusting for a large list of factors I will quote here:
educational attainments, family history of dementia, menopausal status with hormone use status, total energy intake, regular antidepressant drug use, history of depression, BMI, moderate-to-vigorous physical activity, neighborhood SES [socioeconomic status], marital status, living arrangement, smoking status, histories of hypertension, diabetes, and hypercholesterolemia and intakes of sugar-sweetened beverages, fruits, vegetables, whole grains, poultry, fish, eggs, nuts and legumes, low-fat dairy products, high-fat dairy products, and alcohol
I recall last time I looked up the nurses study, they not only didn’t control for sugar, they deliberately made it difficult to do. My favourite example is “hamburger”. There is no category for fast food other than that and similar entries like “hotdogs”. Hamburger is classed as red meat with no telling what else was in the meal; hotdogs is processed meat, again with no indication as to what is consumed with it
So maybe it’s the bread wrapping the meat that was bad
Maybe it was the sauces
Maybe it was the french fries
Maybe it was the drink