Depression is a prevalent mental disorder in older adults, but the prevalence in older adults varies largely across studies due to differences in regional cultures and screening tools. The objective of this review is to systematically evaluate the global prevalence of depression in older adults. PubMed, Embase, Web of Science and Cochran Library databases were searched independently from 2000 to 2021. Subgroups, sensitivity, and meta-regression analyses were performed to address heterogeneity. Publication bias was evaluated using Egger's test. Forty-eight eligible studies were included in this review. The global prevalence of depression in older adults was 28.4%, with high between-study heterogeneity. The meta-analysis showed that the prevalence of depression in older adults is high although it varied with geographic regions, screening tools, sample sizes and representativeness, and study quality. Therefore, it is necessary to carefully consider appropriate screening tools to estimate the prevalence in different regions of a population.

Physical Activity and Mental Health in the Elderly The aging process is closely linked to physiological changes. These physiological changes may lead to an increased vulnerability for developing somatic and mental disorders. Reduced physical activity/sedentary behaviour can enhance this process. In contrast, physical training and sports counteract this process, in particular in the elderly, who may thus gain or maintain a younger biological age. Physical fitness is associated with better mental health in the elderly. Sports and physical activity over the course of life have shown to be of preventive value concerning the development of depression and dementia in old age. Also late-life depression and cognitive impairment (MCI, mild cognitive impairment) can be improved by regular, continuous physical exercise. Some data furthermore suggest that even patients with dementia benefit from physical exercise, especially on behalf of the behavioural and psychic symptoms of dementia (BPSD).