Table 2.

Association of patient characteristics and other factors with the incidence of self-reported COVID-19-like illness in the Netherlands

Factor	n	Person-weeks	Incidence rate	Unadjusted RR (95% CI)	Adjusted RRa (95% CI)
(All)	7060	131 404	54	–	–
Sex
Male	2403	52 556	46	0.78 (0.74–0.82)	0.80 (0.76–0.84)
Female	4657	78 848	59	Ref.	Ref.
Age group (years)
15–24	280	4878	57	1.01 (0.89–1.15)	0.93 (0.82–1.06)
25–34	1344	24 119	56	0.97 (0.91–1.04)	1.01 (0.94–1.08)
35–44	1753	30 804	57	Ref.	Ref.
45–54	1686	30 094	56	0.99 (0.93–1.06)	1.01 (0.94–1.08)
55–64	1344	30 804	54	0.96 (0.89–1.03)	1.00 (0.93–1.08)
65+	663	16 833	39	0.70 (0.64–0.77)	0.77 (0.70–0.85)
Education level
None/primary	338	4685	72	1.18 (1.05–1.32)	1.13 (1.01–1.27)
Middle	3047	49 887	61	Ref.	Ref.
Higher	3675	76 832	48	0.78 (0.74–0.82)	0.84 (0.80–0.88)
Ever smoker	1426	19 034	50	1.50 (1.41–1.59)	1.36 (1.28–1.44)
Pre-existing health condition
Asthma	948	8920	106	2.15 (2.01–2.30)	1.65 (1.54–1.77)
Allergy(s)/hay fever	3232	46 680	69	1.53 (1.46–1.60)	1.37 (1.31–1.44)
Diabetes	250	3590	70	1.33 (1.17–1.50)	1.36 (1.20–1.54)
Chronic lung disease	308	2808	110	2.09 (1.86–2.34)	1.69 (1.50–1.90)
Cardiovascular disease	540	7513	72	1.36 (1.24–1.49)	1.46 (1.33–1.60)
1+ children <5 years in household	1059	18 705	57	1.06 (0.99–1.13)	1.11 (1.04–1.19)
1+ children 5–18 years in household	3915	109 678	52	0.82 (0.77–0.87)	1.39 (1.30–1.48)

CI, confidence interval.

^aAdjusted for all covariates, including province of residence (not shown in the table).

Associations with incidence were estimated as RRs using multivariable Poisson regression analysis and the generalised estimating equation approach. The numerator (n) for the incidence rate (per 1000 person-weeks) is the number of self-reported episodes of symptoms matching the COVID-19-like illness case definition; the denominator is the number of person-weeks at risk.