Body mass index and risk of COVID-19 diagnosis, hospitalisat
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A comprehensive understanding of the association between body mass index (BMI) and COVID-19 is still lacking.

This Population-based cohort study aimed to investigate associations between BMI and risk of COVID-19 diagnosis, hospitalisation with COVID-19, and death after a COVID-19 diagnosis or hospitalisation (subsequent death), accounting for potential effect modification by age and sex. Primary care records covering more than 80% of the Catalan population, linked to region-wide testing, hospital, and mortality records were evaluated.

Participants were adults with at least one measurement of weight and height.

-- Researchers included 2 524 926 participants. After 67 days of follow-up, 57 443 individuals were diagnosed with COVID-19, 10 862 were hospitalized with COVID-19, and 2467 had a subsequent death. BMI was positively associated with being diagnosed and hospitalized with COVID-19.

-- Compared to a BMI of 22kg/m 2, the HR of a BMI of 31kg/m 2 was 1.22 (1.19-1.24) for diagnosis, and 1.88 (1.75-2.03) and 2.01 (1.86-2.18) for hospitalization without and with a prior outpatient diagnosis, respectively.

-- The association between BMI and subsequent death was J-shaped, with a modestly higher risk of death among individuals with BMIs less than 19kg/m 2 and a more pronounced increasing risk for BMIs more than 40kg/m 2.

-- The increase in risk for COVID-19 outcomes was particularly pronounced among younger patients.

Conclusively, there is a monotonic association between BMI and COVID-19 diagnosis and hospitalization risks, but a J-shaped one with mortality. More research is needed to unravel the mechanisms underlying these relationships.