In 2020, we were commissioned by the World Health Organization (WHO) to conduct an overview of reviews regarding the extent to which people with diabetes are at increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and/or of suffering from its complications. We published this overview in Diabetes Care in 2021 (1). At the request of the WHO, we updated this review with literature through October 2022. Here, we provide readers with a summary of this update.

Our 2022 searches identified a further 116 included reviews, a full list and characteristics of which can be found online in the revised supplementary material for the 2021 review (1). We updated our effect direction plots accordingly; these can also be found in the revised supplementary material for readers interested in the data underlying the following summaries.

We have notably more data, and updated conclusions, regarding the following points:

  • Meta-analyses were mixed on whether type 1 diabetes predisposes individuals to higher risk from SARS-CoV-2 than type 2 diabetes (six reviews, four of which are new to this update).

  • People with diabetes who use insulin appear to be at higher risk of worse outcomes from SARS-CoV-2 than people with diabetes who do not use insulin; none of the reviews could establish causality (seven reviews, all new to this update).

  • Data are mixed on whether people with diabetes who use dipeptidyl peptidase 4 inhibitors (DPP-4i) are at higher risk than those who do not use DPP-4i (15 reviews, 13 new to this update).

The following points were confirmed with the addition of further reviews consistent with our original conclusions:

  • Data remain insufficient to conclude whether or not diabetes predisposes to infection with coronavirus disease 2019 (COVID-19). Data on prevalence of diabetes in symptomatic/hospitalized COVID-19 cases are heterogeneous, but overall they suggest people with diabetes are overrepresented, particularly in cohorts with more severe disease (65 studies, 23 new to this update).

  • Evidence suggests an approximate doubling of risk of severe disease in people with diabetes (55 studies, 25 new to this update).

  • Evidence is mixed but overall suggests people with diabetes are more likely to be admitted to intensive care units with SARS-CoV-2 than people without diabetes (23 studies, 13 new to this update).

  • All 64 reviews (30 new to this update) that pooled data on mortality found an increased risk for people with diabetes.

  • There was no clear evidence of a difference in risk from COVID-19 between people with diabetes with new-onset versus preexisting diabetes; an increase in the former was noted (three reviews, one new to this update).

  • Higher blood glucose levels, both in the immediate term and longer term, were associated with worse COVID-19 outcomes (11 reviews, 3 new to this update).

  • There remains little evidence regarding the role of comorbidities in increasing risk of worse outcomes from COVID-19 in people with diabetes (six reviews, three new to this update).

  • Metformin use prior to hospitalization with COVID-19 was associated with a clinically meaningful reduction in the risk of death with COVID-19 (15 reviews in total, 11 of which were new to this update). Confounding by indication cannot be ruled out.

The update to the originally published 2021 review, now including data through 2022, can be found in the supplementary material for Hartmann-Boyce et al. at https://doi.org/10.2337/figshare.16629145.

Funding. The WHO commissioned and financially supported this work. K.K. is supported by the National Institute for Health Research (NIHR) Applied Research Collaboration East Midlands and the NIHR Leicester Biomedical Research Centre. K.K. is also chair of the Ethnicity Subgroup of the Scientific Advisory Group for Emergencies. J.S. receives funding from the In Vitro Diagnostics Co-operative, which is funded by the NIHR MedTech In Vitro Diagnostic Co-operatives scheme (reference no. MIC-2016-014). The NIHR Newcastle In Vitro Diagnostics Co-operative is a partnership between Newcastle University and Newcastle upon Tyne Hospitals National Health Service Foundation Trust. P.H., F.C., and L.O.M. are supported by NIHR Applied Research Collaboration East Midlands. E.M. and C.G. are supported by Wellcome Trust Clinical Doctoral Research Fellowships.

The views expressed are those of the author(s) and not necessarily those of the NIHR, the National Health Service, Newcastle University, or the Department of Health and Social Care.

Duality of Interest. S.S. is in receipt of speaker honoraria from AstraZeneca, Boehringer Ingelheim, Janssen, Lilly, MSD, Abbott, Novo Nordisk, SB Communications, OmniaMed Communications, Roche, Napp Pharmaceuticals, NB Medical, and Amgen; advisory board honoraria from AstraZeneca, Lilly, Boehringer Ingelheim, Janssen, Abbott, MSD, Novo Nordisk, Takeda, and Sanofi; educational grants from Boehringer Ingelheim, Lilly, Novo Nordisk, and Takeda; and conference registration and subsistence from Boehringer Ingelheim, Janssen, Lilly, Novo Nordisk, Abbott, and Takeda. K.K. has acted as a consultant or speaker or has received grants for investigator-initiated studies for AstraZeneca, Abbott, Amgen, Bayer, Novartis, Novo Nordisk, Roche, Servier, Sanofi, Lilly, Merck Sharp & Dohme, Boehringer Ingelheim, Oramed Pharmaceuticals, and Applied Therapeutics. No other potential conflicts of interest relevant to this article were reported.

Author Contributions. J.H.-B. conceptualized this work. J.H.-B. drafted the protocol, which was edited and agreed upon by K.R., A.O., E.M., P.H., J.S., F.C., C.G., L.O.M., S.S., and K.K. J.H.-B., K.R., I.O., A.O., E.M., J.M., P.H., J.S., F.C., C.G., L.O.M., O.J., N.S., and S.S. contributed to screening and data extraction. J.H.-B. led the analysis and write-up of the work. All authors reviewed and edited the manuscript. J.H.-B. is the guarantor of this work and, as such, had full access to all the data in the review and takes responsibility for the integrity of the data and the accuracy of the data analysis.

1.
Hartmann-Boyce
J
,
Rees
K
,
Perring
JC
, et al
.
Risks of and from SARS-CoV-2 infection and COVID-19 in people with diabetes: a systematic review of reviews
.
Diabetes Care
2021
;
44
:
2790
2811
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