AbstractThis research investigated the association between prolonged disposable diaper (DD) wearing in infancy and primary enuresis (PNE). As a case–control study, we collected data from 376 children with enuresis and 379 healthy children who were sex- and age-matched at three tertiary care institutions in mainland China from August 2017 to July 2018. The results of adjusted logistic regression showed the odds ratios (95% confidence intervals) for PNE across the categories of age of daytime DD use cessation were as follows: ≥ 25 months: 1.00, 18–24 months: 0.25 (0.17–0.37), and ≤ 17 months: 0.11 (0.06–0.20), independent of age, mother education, residence, toilet training approach, breastfeeding duration, UTI, constipation, anaphylactic disease and family history. After a similar multivariable adjustment, increased age of daytime DD use (per-month) had a positive correlation with PNE, OR = 1.17, 95% CI 1.13–1.20 and non-linear relationship was detected, whose point was 21 months (the effect sizes and the 95%CI on the left and right sides of inflection point were 1.04 (0.99–1.10), P = 0.131 and 1.25 (1.18–1.31), P < 0.001). Subgroup analysis found that the effect of duration of disposable diaper exposure for each additional month, those children had accepted assisted infant toilet training/elimination communication (AITT/EC) practice had a lower risk of PNE (OR = 1.08, 95% CI 1.04–1.12), compared with those without AITT/EC practice (OR = 1.20, 95% CI 1.14–1.27), P for interaction < 0.001. In conclusion, the children diagnosed with primary enuresis after age 5 stopped using disposable diapers at daytime later than the control group. Association between duration of DD exposure and the risk of childhood enuresis is modified by AITT/EC practice. Timely cessation use of disposable diaper and practice AITT/EC may shorten the time to nocturnal continence, and the prospective cohort studies are needed to verify the discoveries.