Digit ratio in autism spectrum disorder versus down syndrome: An anthropometric study in special needs schools of port Harcourt, Nigeria

Background: The second-to-fourth digit ratio (۲D:۴D), obtained by dividing the length of the index finger by that of the ring finger, varies significantly by sex, race, and ethnicity. This ratio has previously been associated with both autism spectrum disorder and Down syndrome. The current study, therefore, examined the ۲D:۴D digit ratio in individuals with these two neurodevelopmental conditions recruited from special needs schools in Port Harcourt, Rivers State, Nigeria. Methods: This cross-sectional descriptive study involved ۲۰۰ participants: ۱۰۰ with Down syndrome and ۱۰۰ with autism. Participants met specific inclusion criteria, including the absence of hand deformities and a confirmed diagnosis. The lengths of the ۲nd and ۴th digits were measured with a digital vernier calliper. SPSS software, version ۱۹, was used for data analysis. Results: Male autistic subjects showed a normal right-hand digit ratio (۰.۹۸ ± ۰.۱۲) but an elevated left-hand ratio (۱.۰۰ ± ۰.۰۱), whereas female autistic subjects displayed normal ratios bilaterally (۱.۰۰ ± ۰.۰۱ left; ۱.۰۰ ± ۰.۰۰ right). Males with Down syndrome exhibited higher-than-normal ratios on both hands (Left: ۱.۰۲ ± ۰.۰۳; right: ۱.۰۱ ± ۰.۰۱), and females showed ratios of ۱.۰۱ ± ۰.۰۱ (Left) and ۱.۰۰ ± ۰.۰۰ (Right). Mean comparisons revealed significant differences (P-Value < ۰.۰۵) between autistic and Down syndrome subjects of both sexes, with individuals with Down syndrome consistently demonstrating higher digit ratios than autistic individuals. Conclusion: Subjects with Down syndrome had significantly higher digit ratios than autistic subjects. This finding confirms that digit ratios are sexually dimorphic and suggests hypermasculinity in autistic males because of their lower digit ratios.

کلیدواژه ها:

Digit Ratio ، Autistic Disorder ، Down Syndrome