Inbreeding and learning disability in Croatian island isolates

Area of Science:

• Human Genetics
• Developmental Pediatrics
• Population Studies

Background:

• Isolated populations can exhibit unique genetic characteristics.
• Inbreeding may influence the prevalence of genetic disorders.
• Learning disability (LD) has a complex etiology, potentially involving genetic factors.

Purpose of the Study:

• To investigate the correlation between inbreeding coefficients (F) and the prevalence of learning disability (LD).
• To assess the genetic contribution to LD in isolated populations on Croatian islands.

Main Methods:

• Prevalence of LD and inbreeding coefficients were determined in 10 villages across five Croatian islands.
• LD was defined as the inability to attend the public school system, assessed at age six.
• Inbreeding coefficients were estimated using Wright's path method based on four ancestral generations in a random adult sample.

Main Results:

• Learning disability prevalence ranged from 0.43% to 2.47%, with inbreeding coefficients from 0.8% to 4.9%.
• A strong positive correlation (r=0.80, p<0.01) was found between inbreeding (F) and LD prevalence.
• The genetic effect of inbreeding (GEI) was 0.69%, contributing to 76.6% of the population-attributable fraction for LD.

Conclusions:

• A significant genetic component, likely involving numerous recessive factors, contributes to learning disability susceptibility in these isolated populations.
• Inbreeding significantly increases the risk and prevalence of learning disabilities in the studied island communities.
• These findings highlight the impact of genetic factors and population structure on neurodevelopmental outcomes.