Background The increase of average life expectancy and, thus, an increase of the number of elderly people, is the source of various problems associated with old age. Alzheimer's disease is the most frequent type of dementia. It is a chronic disease, correlated with age and, thanks to the introduction of innovative diagnosing methods, it is diagnosed more and more frequently. Providing care to a chronically ill family member with Alzheimer's disease is a burden to the caregiver. Depending on the stage of the disease, the caregiver comes across various problems from the side of the person he or she is taking care of. Burden is a term functioning in psychology and in medicine, defined as the consequences resulting from living with a person who is mentally ill. The contemporarily used definition by Zarit takes into consideration both, the physical, emotional, material and social costs of the caregiver’s burden, resulting from providing care to a chronically ill person. The notions of a formal and an informal caregiver do not have clearly and unequivocally specified definitions. The term formal or professional caregiver frequently applies to defining persons who professionally work at institutions such as: hospitals, residential care homes, nursing homes. The term informal caregiver refers to persons providing non-professional care, who are most frequently family members. The term ; s informal caregiver and family caregiver are used interchangeably in literature. The term family caregiver or family care is a notion that is more narrow and limited to persons who are relatives of the person receiving care, whereas an informal caregiver or informal care includes both, persons from the family as well as non-relatives, who undertake care activities. Aim The aim of the paper was the assessment of the functional efficiency of persons with Alzheimer's disease and its impact on the degree of the caregivers’ burden. Material and methods The study group comprised 100 persons providing informal care to persons with Alzheimer's disease and 100 persons with diagnosed Alzheimer's disease. The studies were carried out in the period from December 2017 to September 2019 among caregivers and the people with Alzheimer's disease under their care remaining at the environment of residence as well as using day care centres in the Lesser Poland Province and the Silesia Province. Before commencing the studies, consent was obtained from the Bioethics Committee in Bielsko-Biała and from medical facilities and facilities running day care centres. In order to assess the burden of the caregivers of persons with Alzheimer's disease, the diagnostic poll method was applied using the survey technique and focused history with the use of an own survey questionnaire as well as standardise ; d research tools: the Caregiver Burden Scale, the Daily Life Fatigue Questionnaire, the Instrumental Activities of Daily Living Scale, the Activities of Daily Living Scale, the Abbreviated Mental Test Score. The statistical analysis applied elements of descriptive statistics. In reference to ordinal variables and qualitative variables, number (n) and percent (%) were applied. Spearman's rank correlation coefficient and the multiple correlation coefficient were used for dependence-related analyses. The significance of the correlation coefficient was tested using the Student's t-test. In cases when this was sensible, the multiple regression equation was constructed in reference to the dependence of one variable on other variables (one or several) assuming the most simple, rectilinear shape of the dependence. The analysis of the significance of differences between the mean values in the compared groups was carried out using the Student's t-test, the Mann–Whitney U test and the Chi-squared test. The significance level adopted in all the analyses was α=0.05. Results The disease duration in the persons receiving care with Alzheimer's disease for both groups jointly (Group A and B) was on average 5.0 years. In Group A it was 5.8 years and in Group B it was 4.2 years. The most numerous group of persons taking care of persons with Alzheimer's disease were their children. The persons ; receiving care were mothers of the caregivers – 44.0% (n=22) in Group A vs 40.0% (n=20) in Group B, fathers – 8.0% (n=4) in Group A vs 6.0% (n=3) in Group B. The next group of persons receiving care were spouses: husbands with Alzheimer's disease were per 24.0% (n=12) of persons in Group A and B and wives – 6.0% (n=3) in Group A vs 16.0% (n=8) in Group B. The assessment of the persons receiving care performed according to the Instrumental Activities of Daily Living Scale demonstrated a high lack of efficiency in almost 3/4 of persons with Alzheimer's disease – 72.0% (n=72). In Group A in the IADL scale 86.0% (n=43) of persons were not performing any instrumental activity and in Group B this referred to 58.0% (n=29) of persons. In the scope of the assessment of the basic activities of daily living 43.0% (n=43) of persons were persons with a severe lack of efficiency in both groups (Group A and B). 66.0% (n=33) of the persons receiving care who were staying at home in Group A demonstrated severe disability, whereas in Group B severe disability was demonstrated by 20.0% (n=10) of persons. More than a half, 56.0% (n=56), of all 100 persons receiving care obtained Abbreviated Mental Test Score results which indicated severe impairment of mental capacity. Women constituted the vast majority of caregivers in both, the group of persons receiving care with Alzheimer's disease who were ; staying at home (Group A) – 86.0% (n=43), as well as the persons with Alzheimer's disease using day care centres (Group B) – 78.0%. The age of the caregivers taking care of the persons with Alzheimer's disease ranged between 32 and 84. (Min-32, Max-84). In Group A 52.0% (n=26) of the caregivers of persons with Alzheimer's disease limited the time devoted to professional work, and among the caregivers in Group B this limitation referred to 48.0% (n=24) of persons. A lack of help in the care provided to persons with Alzheimer's disease was declared by 21.0% (n=21) of all caregivers. The vast majority of caregivers, 79.0% (n=79), were receiving help in the scope of providing care to the ill person. The analysed caregivers in Group A and B were devoting a comparable number of hours to care provided to the person with Alzheimer's disease, on average it was 71.3% of the day in both groups. The total result from five subscales of the Caregiver Burden Scale indicates a medium level of burdening of the caregivers of persons with Alzheimer's disease (2.77 points). A high level of the caregivers’ burden referred to the Caregiver Burden Scale in the general strain subscale in both, Group A and B of the analysed subjects (3.07 points vs. 3.16 points). The mean of the isolation subscale from the Caregiver Burden Scale in Group A indicated a medium level of burden (2.78 points), whereas in ; Group B the level of caregiver burden was high (3.03 points). In subsequent subscales of the Caregiver Burden Scale the results indicated medium burdening of the caregivers in Group A and Group B in the following areas: disappointment (2.84 points vs. 2.82 points), emotional involvement (2.15 points vs. 2.51 points) and environment (2.05 points vs. 2.10 points). The study results demonstrated that the level of fatigue with daily life among caregivers of persons with Alzheimer's disease in both groups (Group A and B), measured using the Daily Life Fatigue Questionnaire for the general mean value was 9.76±6.05 points out of 24 points possible to achieve. The multiple correlation coefficient for the dependent variable of caregiver burden according to the Caregiver Burden Scale - total score for the analysed group (Group A and B) demonstrated significant correlation with the necessity of the constant presence of the caregiver with the person receiving care (R=0.4201; p=0,0001). The multiple correlation coefficient in the general score of daily life fatigue among caregivers in Group A was R=0.5042; p=0.0010 and in Group B it was R=0.3015; p=0.0334. The coefficient of determination in Group A indicated R2=25.42% vs R2=9.0% in Group B. The level of daily life fatigue in caregivers providing care to persons who used day care centres was lower by about 16.0% than in caregivers provid ; ing care to persons who were only staying at home. Conclusions Among all caregivers of persons with Alzheimer's disease, a medium level of burden was demonstrated. The factors determining the burdening of caregivers of persons with Alzheimer's disease in the analysed group were, from the side of the persons receiving care: their level of efficiency in the scope of instrumental and basic activities of daily living, the level of mental capacity, the co-occurrence of an additional disease in the person receiving care, and from the side of the caregiver: the period of providing care and the time devoted to providing care during the day, the necessity for constant presence, the degree of satisfaction with the care provided by doctors and being a relative of the person receiving care.