Introduction: Care of patients with Alzheimer's disease (AD) is so demanding that it can trigger states of physical, emotional and psychological distress among caregivers. The aims of this study were to determine the factorial structure of the Zarit Burden Scale (BS), to establish the differences among the factors according to the characteristics of patients and caregivers, and to determine the effect of the course of the disease on the factors on the BS over a period of two years.
Subjects and methods: We conducted a prospective, longitudinal study on non-professional caregivers of patients with AD. The study involved 463 patients with a diagnosis of probable AD. The mean age was 75.2 years. All the subjects were administered the study protocol on a six-monthly basis over a period of 24 months. The patient's cognitive and functional capacity and the presence of psychological and behavioural symptoms were evaluated. The main caregiver was asked to complete the Zarit BS.
Results: The 21 items on the BS were distributed into five factors that accounted for 59.7% of the total variance of the score. A multivariate analysis identified aggressiveness, apathy, irritability, the caregiver's age and his or her relation to the family as the main causes of distress.
Conclusions: This study confirms the multidimensional structure of the BS and offers information about the effect exerted on burden by the different clinical variables of the patients and the sociodemographic variables of the caregivers.