Environmental factors associated with incidence of developmental dysplasia of the hip: a systematic review and meta-analysis

BACKGROUND: Established associated factors for DDH include female sex, breech presentation, family history, congenital malformations, oligohydramnios, and maternal hyperthyroidism. However, evidence for environmental factors that may contribute to DDH is limited and inconsistent. METHODS: A systematic review of medical literature was conducted to collect data on environmental factors, including latitude, longitude, average yearly precipitation, average yearly temperature, minimum monthly temperature, and maximum monthly temperature, from all institutions that published articles on DDH. Univariate linear regression analysis was used to examine the correlation between environmental factors and DDH incidence, while multiple regression analysis was conducted to identify significant associated factors for DDH incidence. RESULTS: Data from a total of 93 unique manuscripts were analyzed, revealing a significant negative correlation between DDH incidence and temperature, including average yearly temperature (r = -0.27, p = 0.008), minimum monthly temperature (r = -0.28, p = 0.006), and maximum monthly temperature (r = -0.23, p = 0.029). Additionally, there was a significant positive correlation between DDH incidence and latitude (r = 0.27, p = 0.009), and a significant negative correlation between DDH incidence and average yearly precipitation (r = -0.29, p = 0.004). In the final multiple regression analysis, temperature, including average yearly temperature, minimum monthly temperature, and maximum monthly temperature, were identified as significant associated factors for DDH incidence. CONCLUSION: The findings of this study suggest an association between cold weather and DDH incidence. Further research should explore the link between cold weather and DDH incidence, offering insights into potential interventions for cold climates.