The effects of the first UK lockdown for the COVID-19 pandemic on primary-care-recorded cancer and type-2 diabetes mellitus records: A population-based quasi-experimental time series study

Background: COVID-19 disrupted consulting behaviour, healthcare delivery and cancer diagnostic services. This study quantifies the cancer incidence coded in UK general practice electronic health records and deviations from historical trends after the March 2020 national lockdown. For comparison, we study the coded incidence of type-2 diabetes mellitus, which is diagnosed almost entirely within primary care.

Methods: Poisson interrupted time series models investigated the coded incidence of diagnoses in adults aged ≥ 18 years in the Clinical Practice Research Datalink before (01/03/2017-29/02/2020) and after (01/03/2020-28/02/2022) the first lockdown. Datasets were stratified by age, sex, and general practice per 28-day aggregation period. Models captured incidence changes associated with lockdown, both immediately and over time based on historical trends.

Results: We studied 189,457 incident cancer and 191,915 incident diabetes records in 1480 general practices over 52,374,197 person-years at risk. During 01/03/2020-28/02/2022, there were fewer incident records of cancer (n = 22,199, 10.49 %, 10.44-10.53 %) and diabetes (n = 15,709, 7.57 %, 7.53-7.61 %) than expected. Within cancers, impacts ranged from no effect (e.g. unknown primary, pancreas, and ovary), to small effects for lung (n = 773, 3.11 %, 3.09-3.13 % fewer records) and female breast (n = 2686, 6.77 %, 6.73-6.81 %), to the greatest effect for bladder (n = 2874, 31.15 %, 31.00-31.31 %). Diabetes and cancer records recovered maximally to 86 % (95 %CI 80.3-92.7 %) and 74 % (95 %CI 70.3-78.6 %) in July 2021 and May 2021, respectively, of their expected values, declining again until the study end.

Conclusion: The "missing" cancer and diabetes diagnoses in primary care may comprise delayed or missed diagnoses, reduced incidence associated with excess deaths from COVID-19, and potentially increased non-coded recording of diagnoses. Future validation studies must quantify the concordance between primary care and National Cancer Registration Data and Hospital Episode Statistics over the pandemic era.