Exploring risk factors for axial length elongation: a population-based cohort study of 9195 eyes in Japan.

To investigate long-term axial length (AL) changes in adults and to identify risk factors contributing to excessive AL elongation, which is associated with high myopia, we analysed a large dataset of adults without ocular pathology from the Tohoku Medical Megabank Project Community-based Cohort Study in Japan. We conducted a longitudinal investigation of 9195 participants aged ≥20 years with several years of follow-up (mean 3.5 years). Based on the upper quartile of AL elongation for people aged in their 20s, we defined AL elongation exceeding 0.033 mm per year as high AL elongation (HALE). We used multiple logistic regression analyses to assess potential risk factors for HALE. A longitudinal investigation revealed that AL can fluctuate and even become elongated during adulthood, particularly among middle-aged and older individuals. Notably, HALE occurred in 618 out of 9195 eyes (6.7%). The proportion in each age group, comprising people aged in their 20s, 30s, 40s, 50s, 60s, 70s and 80s, was 24.7%, 12.7%, 9.4%, 5.2%, 4.5%, 4.0% and 1.4%, respectively. In addition, we also observed that younger age (OR 1.45 per 10 years older), female gender (OR 1.63), high myopia (OR 2.74) and serum immunoglobulin E (IgE) levels >171 IU/mL (OR 1.27) were associated with HALE. Findings from a large prospective cohort study confirmed that in Japanese individuals, HALE was significantly associated with high serum IgE levels, as well as with younger age, female gender and pre-existing high myopia.