Human social isolation and stress: a systematic review of different contexts and recommendations for future studies

Abstract Objectives The emergence of the coronavirus disease 2019 (COVID-19) pandemic and subsequent lockdowns and social distancing measures adopted worldwide raised questions about the possible health effects of human social isolation. Methods We conducted a systematic review on PubMed, Scopus, and Embase electronic databases using terms related to human social isolation - defined as the isolation of an individual from regular routines and usual social contact - and psychological stress, searching for simulated or naturalistic isolation environments. We present the main results, as well as the validity and limitations of each model. PROSPERO registry number: CRD42021241880. Results Despite the diversity of contexts reviewed, some outcomes almost ubiquitously relate to psychological stress, i.e., longer periods, expectation of a longer period, confinement, lack of social interaction, and support. Based on the results, and considering that most studies were not designed for the purpose of understanding isolation itself, we propose a group of recommendations for future experimental or naturalistic research on the topic. Conclusion Evidence on the impact of different situations in which individuals are subjected to social isolation can assist in development of directed preventive strategies to support people under similar circumstances. Such strategies might increase the general public's compliance with social distancing as a non-pharmacological intervention for emerging infectious diseases.

Mudança de fotoperíodo: proposta de modelo experimental / Change of photoperiod: proposal for an experimental model

Introduction: There are some physiological and behavioral variations related to seasonality, and light is the major synchronizer of these variations according to the seasonal functions in temperate latitudes. Thus, the objective of this study was to validate a methodology for photoperiod modification in Wistar rats byevaluating its interference in the biological rhythm. Methods: Three male adult Wistar rats (60 days) were exposed to 3 photoperiods of 17 days each, with different light/dark cycles (LD): LDPP/SDPP Animal, exposed to initial LD 16:30/07:30 (LDPP, long-day photoperiod) and final LD 07:30/16:30 (SDPP, short-day photoperiod); SDPP/LDPP Animal, exposed to initial LD 07:30/16:30 and final LD 16:30/07:30; and final LD 16:30/07:30; and CT Animal, under constant LD 12:00/12:00. LDPP/SDPP and SDPP/LDPP animals underwent an intermediate photoperiod between initial and final LD, in which light exposure was increased or reduced by 30 min each day until the photoperiods were inverted. All animals remained isolated during the study and had their core temperatures continuously measured by sensors implanted in the peritoneal cavity and their locomotive activity assessed by sensors attached to their cages. The data obtained were used to construct histograms. Results: LDPP/SDPP and SDPP/LDPP animals had a longer period of activity in the SDPP than in the LDPP. The temperature of the CT animal followed a rhythmic pattern. The rat strain used was sensitive to changes in photoperiod. Conclusions: The model proposed and validated in this study can be used in experiments that aim to assess the consequences of changes in light exposure.

Introdução: Existem variações fisiológicas e comportamentais relacionadas à sazonalidade, e a luz é o principal sincronizador destas variações de acordo com as funções sazonais em latitudes de climas temperados. Sendo assim, o objetivo deste estudo foi validar uma metodologia de modificação de fotoperíodo com ratos Wistar avaliando sua interferência no ritmo biológico. Métodos: Três ratos Wistar machos adultos (60 dias) foram expostos a 3 fotoperíodos de 17 dias cada, com diferentes ciclos claro/escuro (light/dark, LD): Animal CL/CC, exposto a LD inicial 16:30/07:30 (CL, claro longo) e LD final 07:30/16:30 (CC, claro curto); Animal CC/CL, exposto a LD inicial 07:30/16:30 e LD final 16:30/07:30; e Animal CT, sob LD constante 12:00/12:00. Os animais CL/CC e CC/CL passaram por um fotoperíodo intermediário entre o LD inicial e final, no qual a exposição à luz foi aumentada ou diminuída em 30 min a cada dia até que os fotoperíodos se invertessem. Todos os animais permaneceram isolados durante o estudo e tiveram suas temperaturas corporais continuamente aferidas por sensores implantados na cavidade peritoneal e suas atividades locomotoras medidas por sensores acoplados às suas caixas. Os dados obtidos foram utilizados para construção de histogramas. Resultados: Os animais CL/CC e CC/CL apresentaram maior período de atividade em CC do que em CL. A temperatura do animal CT seguiu um padrão rítmico. A linhagem utilizada apresentou sensibilidade à mudança de fotoperíodo. Conclusão: O modelo proposto e validado neste estudo pode ser usado em experimentos que tenham como objetivo avaliar as consequências das mudanças de exposição à luz.