Eating processed red meat, like bacon and sausages, is linked to a 16% higher dementia risk. This alarming finding highlights the importance of dietary choices in protecting cognitive function as we age.

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