Table 3.

Dose–response relationship between four exposure variables related to public playgrounds and developing HFMD in Binyang County, Guangxi, China

Variable	Crude OR (95% CI)	Adjusted OR* (95% CI)	P value
Number of public playgrounds visited in previous 2–7 days
0 (reference)
1	5·40 (2·91–10·02)	5·44 (2·45–12·10)	<0·001
⩾2	9·51 (3·57–25·38)	8·12 (2·57–25·68)
Frequency of visits in previous 2–7 days
0 (reference)
1–3	2·13 (0·95–4·76)	1·77 (0·63–4·95)
4–7	3·27 (1·30–8·24)	4·82 (1·28–18·07)	<0·001
⩾8	16·31 (6·37–41·71)	13·58 (4·78–38·54)
Average duration per exposure in previous 2–7 days (min)
0 (reference)
1–14	2·88 (0·55–15·15)	1·23 (0·16–9·71)
15–60	5·52 (2·95–10·33)	6·43 (2·84–14·53)	<0·001
>60	11·02 (3·84–31·60)	8·75 (2·47–31·08)
Total exposure duration in previous 2–7 days (min)
0 (reference)
1–240	2·01 (0·96–4·21)	2·13 (0·83–5·44)
241–600	16·18 (4·72–55·48)	14·53 (3·58–58·90)	<0·001
>600	16·82 (5·75–49·16)	16·51 (4·65–58·68)

OR, Odds ratio; CI, confidence interval.

^*Adjusted for the exposure variables shown in Table 2.