Background Centenarians often represent one of the best examples of aging successfully. However, the role of body composition or hydration status assessed with bioelectrical impedance analysis (BIA) is poorly explored in this population. Therefore, the aim of this systematic review was to better understand the use and the role of BIA for evaluating body composition and hydration status in centenarians. Methods We conducted a systematic review of the literature up to the 1st of May, 2022 for published articles providing data on BIA to evaluate body composition parameters or hydration status in centenarians. Data were summarized descriptively because a meta-analysis was not possible due to the scarcity of available studies. Results Among 2222 articles screened, four were eligible including 291 centenarians (mean age: 100.5 years) who were mainly women (88%). In one study, BIA overestimated fat-free mass and underestimated fat mass when compared to deuterium oxide dilution. Another study carried out in Italy including 14 centenarians found a significant correlation between BIA and fat-free mass evaluated using anthropometric tools. In one study, BIA showed a significant agreement with anthropometric measures of fat mass. In the same sample, sarcopenia and dehydration, evaluated with BIA, had a high prevalence. Conclusion BIA may be used for assessing body composition in centenarians, but research is limited to a few studies suggesting the need of future research in this area.

Background Only limited studies analyzed a possible relationship between frailty and infections. Our aim was to investigate the possible association between higher multidimensional prognostic index (MPI) values, a tool for evaluating multidimensional frailty, and the prevalence of infectious diseases, including antibiotics’ cost and the prevalence of MDR (multidrug resistance) pathogens. Methods Older patients, affected by COVID-19, were enrolled in the hospital of Palermo over four months. Results 112 participants (mean age 77.6, 55.4% males) were included. After adjusting for potential confounders, frailer participants had a higher odds of any positivity to pathogens (prevalence: 61.5%, odds ratio = 15.56, p < 0.0001) compared to a prevalence of 8.6% in more robust, including MDR, and a higher costs in antibiotics. Conclusions Higher MPI values, indicating frailer subjects, were associated with a higher prevalence of infections, particularly of MDR pathogens, and a consequent increase in antibiotics’ cost. Supplementary Information The online version contains supplementary material available at 10.1007/s40520-023-02386-y.