Higher buccal mtDNA content is associated with residential surrounding green in a panel study of primary school children.

Background: Mitochondria are known to respond to environmental stressors but whether green space is associated with mitochondrial abundance is unexplored. Furthermore, as exposures may affect health from early life onwards, we here evaluate if residential green space is associated with mitochondria DNA content (mtDNAc) in children.

Methods: In primary schoolchildren (COGNAC study), between 2012 and 2014, buccal mtDNAc was repeatedly (three times) assessed using qPCR. Surrounding low (<3m), high (≥3m) and total (sum of low and high) green space within different radii (100m-1000m) from the residence and distance to the nearest large green space (>0.5ha) were estimated using a remote sensing derived map. Given the repeated measures design, we applied a mixed-effects model with school and subject as random effect while adjusting for a priori chosen fixed covariates.

Results: mtDNAc was assessed in 246 children with a total of 436 measurements (mean age 10.3 years). Within a 1000m radius around the residential address, an IQR increment in low (11.0%), high (9.5%), and total (13.9%) green space was associated with a respectively 15.2% (95% CI: 7.2%-23.7%), 10.8% (95% CI: 4.5%-17.5%), and 13.4% (95% CI: 7.4%-19.7%) higher mtDNAc. Conversely, an IQR increment (11.6%) in agricultural area in the same radius was associated with a -3.4% (95% CI: 6.7% to -0.1%) lower mtDNAc. Finally, a doubling in distance to large green space was associated with a -5.2% (95% CI: 7.9 to -2.4%) lower mtDNAc.

Conclusion: To our knowledge, this is the first study evaluating associations between residential surrounding green space and mtDNAc in children. Our results showed that green space was associated with a higher mtDNAc in children, which indicates the importance of the early life environment. To what extent these findings contribute to later life health effects should be further examined.