There are around 20 studies identifying the prevalence of chronic loneliness and chronic social isolation in older adults. However, there is an absence of a systematic review, meta-analysis and meta-regression that consolidates the available observational studies. Therefore, our objective was to address this knowledge gap. Here, we present the study protocol for this upcoming work. Such knowledge can help in addressing older individuals at risk for chronic loneliness and chronic social isolation.

Established electronic databases will be searched. Observational studies reporting the prevalence of chronic loneliness and chronic social isolation among individuals aged 60 years and over will be included. Disease-specific samples will be excluded. The focus of data extraction will be on methods, sample characteristics and key findings. The Joanna Briggs Institute (JBI) standardised critical appraisal instrument for prevalence studies will be used for assessing the quality of the studies. Two reviewers will be responsible for carrying out the study selection, data extraction and assessment of study quality. The results will be presented through the use of figures, tables, narrative summaries and a meta-analysis and meta-regression.

No primary data will be collected. Thus, there is no need for approval from an ethics committee. We intend to share our results through publication in a peer-reviewed journal.

Imprecise nutritional recommendations due to a lack of diagnostic test accuracy are a frequent problem for individuals with adverse reactions to foods but no precise diagnosis. Consequently, patients follow very broad and strict elimination diets to avoid uncontrolled symptoms such as diarrhoea and abdominal pain. Dietary limitations and the uncertainty of developing gastrointestinal symptoms after the inadvertent ingestion of food have been demonstrated to reduce the quality of life (QoL) of affected individuals and subsequently might increase the risk of malnutrition and intestinal dysbiosis. This trial aims to investigate the effects of a tailored diet based on the confocal laser endoscopy (CLE) examination result to limit the side effects of unspecific and broad elimination diets and to increase the patient’s QoL.

The study is designed as a prospective, double-blind, monocentric, randomised and controlled trial conducted at the University Hospital of Schleswig-Holstein, Campus Lübeck, Germany. One hundred seventy-two patients with non-IgE-related food allergies and positive CLE results will be randomised to either a tailored diet or a standard fivefold elimination diet. The primary endpoints are the difference between the end and the start of the intervention in health-related QoL and the sum score of the severity of symptoms after 12 weeks. Key secondary endpoints are changes in the severity of symptoms, further QoL measurements, self-assessed state of health and number of days with a pathologically altered stool. Microbiome diversity and metabolome of stool, urine and blood will also be investigated. Safety endpoints are body composition, body mass index and adverse events.

The study protocol was accepted by the ethical committee of the University of Lübeck (AZ: 22-111) on 4 May2022. Results of the study will be published in peer-reviewed journals and presented at scientific meetings.

German Clinical Trials Register (DRKS00029323).