Atopic status
Fifty-seven participants (10.7% of the study population) were atopic
and showed a history of allergy to seasonal and/or perennial airborne
allergens (either rhino-conjunctivitis or bronchial asthma). Of these,
32 (56.1%) were females (mean age 62±14, range 28-93 years). Atopic
subjects were younger than non-atopic patients were (69±14 years, p =
0.01), and showed a lower prevalence of coronary heart disease (p
<0,050). Notably, atopic subjects showed a much lower
occurrence of severe or very severe COVID-19-related pulmonary
involvement (33.3% vs 67.7% in non-allergic individuals, p
<0.0001), and therefore a milder disease course. The
protective effect of atopic status against severe lung disease was
evident throughout all the age subset evaluated, particularly in
patients below 60 years of age (p = 0.001) (Figure 1). Intriguingly, a
reduced cumulative incidence of death was observed among atopic subjects
(8.8% vs 18.9%; p = 0.059), albeit it did not reach statistical
significance due to the small number of observations. The multiple
logistic regression analysis was first performed including as potential
confounders age, sex, smoking, and all the comorbidities. Since none of
the comorbidities did contribute to the estimates, we excluded them from
the final model, while we decided to still keep age. The adjusted
estimate confirmed a significant association between atopic status and
reduced severity of COVID-19: in fact, while adjusting for sex, age, and
smoking status, non-atopic patients had a significantly higher risk of
having severe Covid-19 (ORadj 3.0, 95% confidence
interval 1.6-5.7, p = 0.001) (Table 1).
An unsupervised two-way hierarchical clustering analysis yielded several
original patterns of associated clinical features in our population. The
simultaneous evaluation of distinct comorbidities at the single patient
level generated by the multiple logistic regression analysis identified
a clear cluster between mild COVID-19-related pneumonia and atopy
status, which were strictly associated (p <0.0001; ORa= 4.523,
95% CI= 2.221-9.221) (Figure 2).