Objectives This umbrella review aimed to evaluate whether certain interventions can mitigate the negative health consequences of caregiving, which interventions are more effective than others depending on the circumstances, and how these interventions are experienced by caregivers themselves.

Design An umbrella review of systematic reviews was conducted.

Data sources Quantitative (with or without meta-analyses), qualitative and mixed-methods systematic reviews were included.

Eligibility criteria Reviews were considered eligible if they met the following criteria: included primary studies targeting informal (ie, unpaid) caregivers of older people or persons presenting with ageing-related diseases; focused on support interventions and assessed their effectiveness (quantitative reviews) or their implementation and/or lived experience of the target population (qualitative reviews); included physical or mental health-related outcomes of informal caregivers.

Data extraction and synthesis A total of 47 reviews were included, covering 619 distinct primary studies. Each potentially eligible review underwent critical appraisal and citation overlap assessment. Data were extracted independently by two reviewers and cross-checked. Quantitative review results were synthesised narratively and presented in tabular format, while qualitative findings were compiled using the mega-aggregation framework synthesis method.

Results The evidence regarding the effectiveness of interventions on physical and mental health outcomes was inconclusive. Quantitative reviews were highly discordant, whereas qualitative reviews only reported practical, emotional and relational benefits. Multicomponent and person-centred interventions seemed to yield highest effectiveness and acceptability. Heterogeneity among caregivers, care receivers and care contexts was often overlooked. Important issues related to the low quality of evidence and futile overproduction of similar reviews were identified.

Conclusions Lack of robust evidence calls for better intervention research and evaluation practices. It may be warranted to avoid one-size-fits-all approaches to intervention design. Primary care and other existing resources should be leveraged to support interventions, possibly with increasing contributions from the non-profit sector.

Umbrella reviews (reviews of systematic reviews) are increasingly used to synthesize findings from systematic reviews. One important challenge when pooling data from several systematic reviews is publication overlap, that is, the same primary publications being included in multiple reviews. Pieper et al. have proposed using the corrected covered area (CCA) index to quantify the degree of overlap between systematic reviews to be pooled in an umbrella review. Recently, this methodology has been integrated in Excel- or R-based tools for easier use. In this short letter, we highlight an important consideration for using the CCA methodology for pairwise overlap assessment, especially when reviews include varying numbers of primary publications, and we urge researchers to fine-tune this method and exercise caution when review exclusion decisions are based on its output.

Background: Excessive blood glucose promotes neuropathological cognitive decline in individuals with type 2 diabetes mellitus and the metabolic syndrome, but no systematic synthesis of the evidence for the same association exists in individuals without these conditions.

Objectives: To systematically review studies exploring the role of glucose on cognition, dementia risk, and related biomarkers in adults without diabetes or metabolic syndrome.

Data sources: We searched databases from inception until July 2021 and manually searched the reference lists of included studies. Risk of bias was assessed using the Joanna Briggs Institute tool.

Results: We found 46 observational studies including approximately 98,216 participants. Substantial heterogeneity in study results precluded drawing definitive conclusion whether blood glucose levels are associated with cognition or dementia risk. Higher blood glucose, however, was associated with greater amyloid burden, brain atrophy, and reduced cortical thickness.

Conclusions and implications: High glucose concentrations in blood may exacerbate dementia-related neuropathology but whether this translates into pathological cognitive decline or elevate dementia risk later in life remains unclear.

Introduction Informal (unpaid) caregivers play an essential role in caring for older people, whose care needs are often not fully met by formal services. While providing informal care may be a positive experience, it can also exert a considerable strain on caregivers’ physical and mental health. How to best support the needs of informal caregivers remains largely debated. This umbrella review (review of systematic reviews) aims to evaluate (1) whether effective interventions can mitigate the negative health outcomes of informal caregiving, (2) whether certain types of interventions are more effective than others, (3) whether effectiveness of interventions depends on caregiver/receiver, context or implementation characteristics and (4) how these interventions are perceived in terms of acceptability, feasibility and added value.

Methods and analysis We will include systematic reviews of primary studies focusing on the effectiveness of interventions (public or private, unifaceted or multifaceted, delivered by health or social care professionals or volunteers) aimed at reducing the impact of caregiving on caregivers’ physical or mental health. This will also include quantitative and qualitative syntheses of implementation studies. The literature search will include the following databases: Medline, CINAHL, PsycINFO and Web of Science. A key informant-guided search of grey literature will be performed. Quality appraisal will be conducted with the AMSTAR-2 checklist for quantitative reviews and with an ad hoc checklist for qualitative syntheses. Narrative and tabular summaries of extracted data will be produced, and framework synthesis will be employed for weaving together evidence from quantitative studies in effectiveness reviews with findings on implementation from qualitative studies.

Ethics and dissemination This umbrella review will use data from secondary sources and will not involve interactions with study participants; it is thus exempt from ethical approval. Results will be presented at international conferences and will be published in a peer-reviewed journal.