Early Life Influences on Hearing in Adulthood: a Systematic Review and Two-Step Individual Patient Data Meta-Analysis.

All included studies were conducted in affluent UK or Scandinavian populations; the findings may not generalise to low- and middle-income countries where early-life nutritional and environmental exposures differ substantially. The meta-analysis could only adjust for age at testing and sex. Gestational age, socioeconomic position at birth, and other potential confounders were not available for the pooled analysis, so residual confounding is possible. Only 2 studies were pooled for birth weight and 4 for height, limiting the robustness of the pooled estimates despite the large total sample sizes. The studies used different hearing measures (pure tone audiometry, speech-in-noise recognition, self-report) and did not distinguish between sensorineural and conductive hearing loss. The design is observational. The authors note that the associations may reflect shared socioeconomic or environmental factors rather than a direct causal effect of early development on hearing. The authors state that the evidence is suggestive rather than definitive and call for further research to address these gaps.

The authors declare no conflict of interest. No funder or sponsor is named in the text.

Do not read these associations as proof that a specific person's birth weight or height caused their hearing loss. The meta-analysis controlled only for age and sex, not for socioeconomic position at birth, gestational age, or other confounders. The effect sizes are small (3% per cm of height, 13.5% per kg of birth weight) and describe population-level shifts, not individual risk. The authors themselves describe the evidence as suggestive rather than definitive.