Aberrations in medically certified sick leave and primary healthcare consultations in Norway in 2023 compared to pre-COVID-19-pandemic trends

Background Since 2022, Norway has employed a vaccine-only COVID-19 strategy. Primary healthcare in Norway uses International Classification of Primary Care version 2 (ICPC-2) codes. This study aims to systematically compare medically certified sick leave and primary healthcare consultations in 2023 with the pre-pandemic 2010–2019 trends, and subsequently estimate the magnitude of these changes. Methods For the respective outcomes of (A) working person-years lost to medically certified sick leave (WYLSL) and (B) number of primary healthcare consultations, 556 and 85 ICPC-2 code combinations were extracted from the Norwegian Labour and Welfare Administration’s sick leave registry and the Norwegian Syndromic Surveillance System. For each ICPC-2 code combination, a Bayesian linear regression was performed using data between 2010 and 2019 to estimate an expected baseline for 2023, which was then used to calculate the deviation from the pre-pandemic trend. A false discovery rate of 5% was used to account for multiple testing. Results All years from 2020 to 2023 had excess WYLSL, corresponding to 14,491 (90% PI: 8,935 to 20,016) in 2020, 12,911 (90% PI: 5,916 to 19,996) in 2021, 21,263 (90% PI: 12,627 to 29,864) in 2022, and 24,466 (90% PI: 14,023 to 34,705) in 2023. This corresponded to an economic loss of approximately 1.5 billion USD in 2023. Excess WYLSL due to A* (General and unspecified) increased from 2020 to 2023, with an estimated excess of 4,136 WYLSL in 2023 (69% higher than expected). More than half of this increase was explained by A04 (Weakness/tiredness general), whose excess WYLSL in 2023 were estimated at 2,640 (80% higher than expected). The excess in A04 (Weakness/tiredness general) corresponded to an economic loss of 161 million USD and accounted for 11% of the total excess WYLSL in 2023. The excess WYLSL in R* (Respiratory) in 2023 was 3,408, which correspond to an economic loss of 207 million USD and accounted for 14% of the total excess in 2023. Conclusions Significant excesses in working person-years lost to medically certified sick leave and primary healthcare consultations in 2023. A sizable proportion of the excesses were due to diseases/symptoms associated with acute and post-acute sequelae of COVID-19.