The survey was designed as a country representative study and was carried out on a sample of Polish residents aged ≥65 years, divided into six age groups of equal size and gender proportion (65-69, 70-74, 75-79, 80-84, 85-89 and 90+ years). The planned size of the research sample was 3,000 subjects (250 subjects for each gender and age group). Research participants were randomly recruited in clusters, in a stratified, proportional draw performed in three stages. The reason for overrepresentation of the oldest age groups was to allow separate analysis of data for older people.