Review question Did caffeine consumption of adults change during the COVID-19 lockdowns? Searches PubMed®, Web of Science® and Embase® databases will be used for all searches. A basic search strategy will be developed for PubMed according to the follow search string: “((caffeine) OR (coffee) OR (energy drinks) OR (nutrition) OR (eating habits) OR (lifestyle)) AND ((covid19) OR (covid) OR (covid-19) OR (Sars-cov-2) OR (lockdown))” and modified accordingly for other research engines. Types of study to be included We will include observational studies (Prospective and retrospective cohort studies and Cross-sectional studies) Condition or domain being studied During the COVID-19 pandemic measures of strict confinement were enforced by governments in several countries to prevent transmission of the virus. According to numerous studies, a change in nutritional habits during the confinement period has been observed. In this study we will investigate the impact of the COVID-19 lockdowns on caffeine consumption among healthy adult individuals. Participants/population Inclusion criteria: Healthy adult individuals or individuals with asymptomatic Covid-19 infection consuming caffeine (coffee, energy drinks, other caffeine containing drinks) Exclusion criteria: • Hospitalized patients • Age <18 years old Intervention(s), exposure(s) Covid-19 first lockdowns Comparator(s)/control Caffeine consumption before the COVID-19 lockdown period Context Main outcome(s) Potential changes on caffeine consumption. Timing and effect measures not applicable. Data extraction (selection and coding) In case of adequate data, our meta-analysis will be performed in accordance with the meta-analyses Of Observational Studies in Epidemiology (MOOSE) statement (Meta-analysis of Observational Studies in Epidemiology. A Proposal for Reporting. JAMA. 2000;283(15):2008-2012. doi: 10.1001/jama.283.15.2008.). Two reviewers will independently extract data regarding changes of caffeine consumption after the lockdown period. Any disagreement will be resolved by a third reviewer. Authors will be contacted in order to obtain any missing data relevant to the analysis. Risk of bias (quality) assessment The quality of the eligible studies will be evaluated using a version of Joanna Briggs Institute Critical Appraisal tools for use in JBI Systematic Reviews (Joanna Briggs Institute 2017https://jbi.global/sites/default/files/2019-05/JBI_Critical_Appraisal-Checklist_for_Analytical_Cross_Sectional_Studies2017_0.pdf). Strategy for data synthesis • Text and tables will be used to provide an explanation of the studys’ characteristics and findings • Table will be used to provide relevant information regarding caffeine consumption (e.g. increase/decrease/no-change) • In case of Meta-analysis, random effects or fixed-effects models will be used and the inverse variance method. We will report effect sizes as mean differences (MD) and their 95% confidence intervals (CI) Analysis of subgroups or subsets In case of adequate data different group of people (e.g., obese/non obese, adults/adolescents) and their caffeine consumption after/during lockdown will be analyzed. Contact details for further information Assoc. Prof. Michail Chourdakis e-mail: mhourd@gapps.auth.gr Organizational affiliation of the review • Aristotle University of Thessaloniki, Thessaloniki, Greece Type and method of review Systematic review and Meta-analysis Anticipated or actual start date 25 October 2021 Anticipated completion date 15 December 2021 Funding sources/sponsors None Conflicts of interest None Language English Country Greece Stage of review Review Ongoing Subject index terms Caffeine; energy drinks; lockdown; COVID-19; SARS-COV-2