Alzheimer’s disease is a progressive neurodegenerative disorder marked by amyloid-β plaque accumulation, neurofibrillary tangles, and neuronal loss, resulting in cognitive decline and death. It is the sixth leading cause of death in the United States, with projected national management costs exceeding $600 billion annually by 2050.

Alzheimer’s disease etiology involves genetic, vascular, and environmental factors, notably diet. Due to the lack of curative treatments and limited pharmacological efficacy, prevention targeting modifiable risk factors is critical. Previous research indicated higher dementia mortality among vegetarians compared to non-vegetarians, despite reduced all-cause and other cause-specific mortalities with vegetarian diets.

Recent studies indicate egg consumption may be associated with Alzheimer’s disease risk, with moderate intake linked to a 10 % reduction in neurodegenerative mortality. However, most studies are limited by design flaws, inconsistent dietary assessment, lack of biomarker validation, and inadequate adjustment for confounders, underscoring the need for rigorous investigation.

The current study exploited the Adventist Health Study-2 (AHS-2) cohort to examine the relationship between egg consumption and Alzheimer’s disease risk, drawing on extensive dietary and health data from over 96,000 participants. AHS-2 data were merged with Medicare claims and deidentified. For this analysis, only US participants aged 65 and older were included, with eligibility based on Medicare records.

A total of 39,498 participants met the eligibility criteria. Dietary intake was measured at baseline with a validated food frequency questionnaire covering over 200 items. Both frequency and quantity of egg intake were recorded, including visible and hidden sources. Egg intake categories ranged from never to five or more times per week, and intake was energy-adjusted.

Alzheimer’s disease incidence was determined from Medicare records, using standard diagnostic codes. Only new cases after enrollment were counted. Cox proportional hazards models with attained age as the time scale were used to estimate the link between egg intake and Alzheimer’s risk.

To provide context for individual food intake, two substitution analyses were conducted to examine the replacement of eggs with nuts/seeds and legumes, which are nutrient-dense, commonly consumed plant-based protein sources in the cohort. These analyses examined how substituting eggs with alternative protein-rich foods might affect the risk of Alzheimer’s disease.