Table 2.

Prevalence of serum antibodies to SARS-CoV-2 and participants' socio-demographic characteristics (N = 1813)

Characteristic	Category/statistics	N	Seroprevalence % (95% CI)	P-valuea	adjusted P-valueb	OR (95% CI)c	OR adjusted P-valuec
Sex	Male	884	28.3 (25.8–31.0)	0.013	0.070	Ref.
	Female	929	23.8 (21.5–26.3)			0.83 (0.68–1.02)	0.070
Smoking habit	Non-smoker	1278	27.6 (25.5–29.8)	<0.001	<0.001	Ref.
	Past smoker	273	31.2 (26.6–36.3)			1.07 (0.82–1.39)	0.609
	Current smoker	262	13.1 (9.8–17.1)			0.35 (0.25–0.49)	<0.001
Main activity	Accomodation and catering	399	31.6 (27.7–35.8)	0.002	<0.001	1.37 (1.05–1.77)	0.019
	Healthcare and social services	59	26.5 (17.9–37.4)			1.26 (0.72–2.20)	0.425
	Other activity	586	26.5 (23.5–29.8)			Ref.
	Student or not active	769	22.5 (20.0–25.2)			0.82 (0.65–1.03)	0.089
Municipality	Ortisei	908	22.6 (20.3–25.1)	<0.001	0.010	Ref.
	Santa Cristina	389	28.3 (24.5–32.5)			1.31 (1.03–1.68)	0.031
	Selva	516	30.2 (26.9–33.9)			1.37 (1.10–1.70)	0.006
Nationality	Italian	1744	26.1 (24.3–27.9)	0.829	0.692	Ref.
	Other	69	25.1 (17.1–35.3)			0.90 (0.53–1.53)	0.692
Education	Primary school or no title	242	23.9 (19.5–28.9)	0.889	0.529	Ref.
	Lower secondary school	397	27.0 (23.4–31.1)			1.19 (0.84–1.68)	0.320
	Vocational school	516	26.6 (23.3–30.1)			1.02 (0.72–1.44)	0.932
	Upper secondary school	463	25.7 (22.4–29.4)			0.97 (0.68–1.39)	0.877
	Higher degree	195	25.7 (20.6–31.6)			0.89 (0.57–1.37)	0.590
Language	German	312	23.6 (19.7–28.1)	0.379	0.454	Ref.
	Italian	161	24.7 (19.3–31.2)			0.88 (0.59–1.32)	0.544
	Ladin	1274	27.1 (25.0–29.3)			1.09 (0.83–1.42)	0.550
	Other	66	21.7 (14.1–31.9)			0.78 (0.44–1.39)	0.403
Age	Median	1813	26.1 (24.2–27.9)	0.168	0.827	Ref.
	Median + 5 years	1813	26.3 (24.5–28.2)			1.00 (0.98–1.03)	0.827
BMId	Mean	1797	25.7 (23.9–27.5)	<0.001	0.023	Ref.
	Mean + 1 s.d.	1797	28.9 (26.3–31.5)			1.14 (1.02–1.28)	0.023

Seroprevalence figures at specific values of age and BMI were obtained by predictive margins with linearised standard errors from a logistic model. BMI, body mass index; s.d., standard deviation.

^aSurvey design adjusted F statistics. For continuous variables (age, BMI), the P-value was obtained by the adjusted Wald test with linearised standard errors.

^bSurvey design adjusted F statistics, multiply adjusted for sex, age, BMI, smoking habit, main activity and municipality. For continuous variables (age, BMI), the P-value was obtained by the adjusted Wald test with linearised standard errors.

^cOdd ratios (ORs), 95% confidence intervals (95% CIs) and related adjusted P-values were obtained by linearised standard errors and logit transformation.

^dThere were 16 missing values.