Birth month is associated with learning capacity in childhood in Northeast China.

It is difficult to evaluate long-term ventilation and indoor-outdoor temperature variation on-site in the birth residence so as to investigate their associations with learning capacity from childhood through adolescence. Here, we conducted a questionnaire-based retrospective cohort study in ten schools from two northeast China cities with warm summers and severe cold winters when residences had very low air exchange rates. Scores for Chinese, Mathematics, and English in the final exams of the summer semester in June 2018 were collected to evaluate learning capacity. We surveyed 6238 students aged 14.7 (SD: 2.1) years old. Using the 2nd quarter (April-May-June) birth as reference, 4th quarter (October-November-December) birth consistently was significantly associated with lower scores in Chinese in bivariate (β, 95%CI: -3.2, -4.3 to -2.0) and multivariate (-1.8, -2.4 to -0.8) linear regression analyses. Stratified sub-analyses showed significant associations for male (-2.4, -3.7 to -1.1), urban (-2.4, -3.4 to -1.4), and primary students (-2.9, -4.5 to -1.4). Since household ventilation and indoor-outdoor temperature variation had great differences between the 2nd and 4th quarter of year, our results suggest that these two factors in the birth residence could be associated with learning capacity in childhood, especially for male and primary students in northeast China.