Table 1 Participant inclusion and exclusion criteria

Inclusion criteria:

• Age 60–77 years

• Fluency in the local language (German, Italian, Finnish, or Swedish)

• CAIDE Risk Score ≥ 6

• Cognition at mean level or slightly lower than expected for age, defined as having at least one of the following: MMSE ≤ 26, Consortium to Establish a registry for Alzheimer’s Disease (CERAD) word list learning ≤ 19/30, and/or CERAD word list delayed recall ≤ 75%

• Sufficient digital skills to follow the intervention program and engage with the digital tools: Internet access, prior experience with smartphone, and an existing compatible smartphone or willingness to switch to a new smartphone provided by LETHE

Exclusion criteria:

• Diagnosed or suspected dementia/substantial cognitive impairment (MMSE < 20); current/past use of Alzheimer’s disease/dementia medication

• Significant neurologic disease e.g., Parkinson’s disease, Huntington’s disease, normal pressure hydrocephalus, brain tumor, progressive supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, or history of significant head trauma with persistent neurologic sequelae or known structural brain abnormalities

• Diminished decision-making capacity, incapability to consent/complete study assessments, and any conditions preventing cooperation (based on clinical judgement)

• Severe loss of vision, hearing, or communicative ability

• Any conditions affecting safe intervention engagement e.g., malignancy, major depression, symptomatic cardiovascular disease, and revascularization within 1 year

• Concomitant participation in an intervention trial (unless considered not to interfere with LETHE)