SynthesisJournal of global health2026
Associations between month/season of birth and health outcomes: an umbrella review of systematic reviews and meta-analyses.
Synthesis in Journal of global health, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
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Corrections and comments
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Authors and funding
5 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Background: The relationship between month or season of birth and long-term health outcomes remains an important but underexplored topic in public health. Evidence suggests that birth timing may influence disease susceptibility and broader health trajectories, reflecting interactions between biological and ecological factors. Clarifying these associations is essential for advancing prevention and a holistic view of health shaped by temporal exposures. Methods: We conducted an umbrella review of systematic reviews and meta-analyses indexed in PubMed, Embase, and Web of Science up to 2 July 2025. Eligible studies reported quantitative estimates for associations between birth month/season and objectively measured health outcomes. We used random-effects models to produce pooled estimates and evaluated heterogeneity, small-study effects, and bias. We graded associations using established class-of-evidence criteria and assessed methodological quality with AMSTAR 2. Results: We included 10 meta-analyses, comprising 614 unique associations (defined as individual pairwise analyses between a specific birth month/season exposure and a distinct health outcome). Of these, 45 associations were statistically significant, and 25 were eligible for evidence grading. No association met class I criteria, but one (January birth and schizophrenia) reached class II. The most consistent findings involved neurodevelopmental and psychiatric outcomes, with winter births linked to a modest increase in schizophrenia risk (odds ratio (OR) = 1.05) and spring births to multiple sclerosis. Most autoimmune, oncological, and perinatal associations were graded as weak (class III-IV) due to small effect sizes or heterogeneity. Conclusions: The strongest evidence for associations between month/season of birth and long-term health outcomes was restricted to specific neuropsychiatric outcomes, with most other associations graded as weak. Grading the credibility of these associations helps distinguish robust signals from exploratory findings, and provides a clear framework for future mechanistic and epidemiological investigations. Registration: PROSPERO: CRD420251110595.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.