Aim: The objective of this study was to assess whether an elderly patient’s frailty was associated with acute kidney injury (AKI) and to examine whether severe frailty group had an increased risk of AKI than mild–moderate group.Methods: We searched The Cochrane Library, PubMed, and EMBASE for relevant studies without language limitations before 1 March 2019 with a priori defined inclusion and exclusion criteria. Five population-based cohort studies were included for systematic review and meta-analysis.Results: Compared with the control group, the frailty group is significantly associated AKI (Odds Ratio = 2.05; 95% CI: 1.23–3.43). The moderate-severe frailty group has an increased risk of AKI than mild frailty group (Hazard Ratio = 2.87; 95% CI: 1.60–5.17.Conclusion: In conclusion, the available best evidence support an association between frailty and AKI among elder patients, thus relevant interventions should be taken among elderly under potential risk of AKI.

Objective: As the reproduction season's effect on the mental health status is unknown, this study aims to explore the association between seasons and postpartum depression. Methods:A comprehensive search in databases, including PubMed, Cochrane Library, and EMBASE, was performed to identify studies reporting the relationship between reproduction season and postpartum depression. The latter was assessed using certain methods. Moreover, the study design and duration, sample size, the definition of four seasons, outcome assessment, method, and conclusion were extracted. Two independent authors screened the studies independently, and PRISMA 2020 was used as the reporting standard (PRISMA registration ID is 284524).Results: A total of five studies including 103,986 participants met our criteria. In the sensitivity analysis, the result of the meta-analysis shows that women who gave birth in spring, summer, or autumn had a lower risk of postpartum depression compared to those who gave birth in winter (RR: 0.83; 95% confidence interval [CI]: 0.78-0.88). Conclusion:Women who gave birth in the other seasons were less likely to have postpartum depression compared to those who gave birth in winter. This result could help couples make overall decisions and help the puerpera take preventive measures against postpartum depression.