Table 4. ORs (95% CIs) for hearing loss^a by joint effect between earphone use time and blood lead level (n = 1,036).

Variables	Low lead	High lead	Lead within strata of using time
Low using time	Ref.	1.14 (0.42, 3.13)	1.14 (0.42, 3.13)
High using time	1.79 (0.66, 4.85)	3.23 (1.44, 7.27)	1.93 (0.75, 4.96)
Using time within strata of lead	1.79 (0.66, 4.85)	2.48 (0.97, 6.38)

^aHearing loss was defined as pure-tone average ≥ 25 dB.

Measure of interaction on additive scale: RERI (95% CI) = 1.30 (−0.83 to 3.43); p = 0.232.

Measure of interaction on multiplicative scale: ratio of ORs (95% CI) = 1.58 (0.42 to 5.97); p = 0.499.

Models were adjusted for age, sex, monthly income, education levels, smoking status, BMI, occupational noise, loud noise, firearm noise, hypertension, and diabetes. Earphone use time models were further adjusted for lead, and blood lead models were further adjusted for earphone use time.