Serum glucose, lactate dehydrogenase and hypertension are mediators of the effect of body mass index on severity of COVID-19.

Background: COVID-19 has a broad clinical spectrum. We investigated the role of serum markers measured on admission on severity as assessed at discharge and investigated those which relate to the effect of BMI on severity.

Methods: Clinical and laboratory data from 610 COVID-19 cases hospitalized in the province of Zheijang, China were investigated as risk factors for severe COVID-19 (assessed by respiratory distress) compared to mild or common forms using logistic regression methods. Biochemical markers were correlated with severity using spearman correlations, and a ROC analysis was used to determine the individual contribution of each of the biochemical markers on severity. We carried out formal mediation analyses to investigate the extent of the effect of body mass index (BMI) on COVID-19 severity mediated by hypertension, glycemia, Lactose Dehydrogenase (LDH) at the time of hospitalization and C-Reactive Protein levels (CRP), in units of standard deviations.

Results: The individual markers measured on admission contributing most strongly to prediction of COVID-19 severity as assessed at discharge were LDH, CRP and glucose. The proportion of the effect of BMI on severity of COVID-19 mediated by CRP, glycemia or hypertension, we find that glucose mediated 79% (p < .0001), LDH mediated 78% (p < .0001), hypertension mediated 66% (p < .0001); however, only 44% (p < .005) was mediated by systemic inflammation (CRP).

Conclusion: Our data indicate that a larger proportion of the effect of BMI on severity of COVID-19 is mediated by glycemia and LDH levels whereas less than half of it is mediated by systemic inflammation.