Autism Spectrum Disorder (ASD) is a neurodevelopmental condition that affects communication, behavior, sensory processing, and daily functioning. Recent research suggests that the gut microbiome, the community of microorganisms living in the gastrointestinal tract, may influence brain development and function through the gut-brain and gut-motor axes. Alterations in gut microbiome characteristics have been reported in children with ASD and may be associated with differences in neurodevelopmental outcomes. This observational study aims to investigate the association between gut microbiome characteristics and neurodevelopmental functioning in children with ASD. The study will evaluate multiple domains of functioning, including motor performance, sensory processing, behavior, cognition, sleep, and participation in daily activities. Gut microbiome characteristics will be assessed using stool sample analysis, and neurodevelopmental outcomes will be measured using standardized assessments and validated questionnaires. The findings of this study may improve understanding of the relationship between the gut microbiome and neurodevelopmental functioning in children with ASD and provide insights into the role of the gut-motor axis in shaping functional outcomes. This knowledge may support future research and contribute to the development of more personalized approaches to assessment and rehabilitation in ASD.
Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by impairments in social communication, restricted and repetitive behaviors, sensory processing differences, and variable functional abilities across developmental domains. Increasing evidence suggests that the gut microbiome may play a role in neurodevelopment through bidirectional communication pathways linking the gastrointestinal system and the central nervous system. These interactions, commonly described as the gut-brain axis, have been implicated in behavioral, cognitive, sensory, and motor processes. More recently, the concept of the gut-motor axis has emerged, highlighting potential relationships between gut microbial composition and motor functioning. Several studies have reported alterations in gut microbiome composition among children with ASD compared with typically developing peers. However, existing research has largely focused on autism symptom severity, behavioral manifestations, or gastrointestinal symptoms, while the association between gut microbiome characteristics and broader neurodevelopmental functioning remains insufficiently explored. Furthermore, few studies have examined multiple functional domains simultaneously within a rehabilitation framework. The present study aims to investigate the association between gut microbiome characteristics and neurodevelopmental functioning in children with ASD. A multidomain assessment approach will be employed to evaluate neurodevelopmental outcomes encompassing motor performance, sensory processing, behavioral function, cognitive functioning, sleep, and participation in daily activities. Gut microbiome characteristics will be assessed through stool sample analysis using established microbiological methods. Neurodevelopmental outcomes will be evaluated using standardized assessments and validated caregiver-reported instruments. By examining the relationship between gut microbiome characteristics and multidimensional functional outcomes, this study seeks to enhance understanding of the gut-motor axis in ASD and identify potential microbiome-related factors associated with neurodevelopmental functioning. The findings may contribute to the growing body of evidence on microbiome-neurodevelopment interactions and inform future translational and rehabilitation research in children with ASD.
Study Type
OBSERVATIONAL
Enrollment
600
Saveetha Medical College and Hospital
Chennai, Tamil Nadu, India
Indian Scale for Assessment of Autism
Autism severity will be assessed using the Indian Scale for Assessment of Autism (ISAA). The ISAA total score ranges from 40 to 200, with higher scores indicating greater autism symptom severity (worse outcomes) and lower scores indicating less severe autism-related impairments (better outcomes). The total score will be used to determine the severity of autism symptoms and examine associations with gut microbiome characteristics.
Time frame: Baseline
Gut Microbiome Diversity and Composition
Gut microbiome characteristics will be assessed from stool samples using 16S rRNA gene sequencing. Primary microbiome outcomes will include alpha diversity indices (Shannon Diversity Index, Simpson Diversity Index, and Chao1 Richness Index), beta diversity measures, and the relative abundance of bacterial taxa. These measures will be used to characterize gut microbial diversity and composition in children with Autism Spectrum Disorder.
Time frame: Baseline (single stool sample collected at study enrollment)
Gross Motor Function Measure-88 Total Score
Gross motor function will be assessed using the Gross Motor Function Measure-88 (GMFM-88). The GMFM-88 evaluates gross motor performance across five dimensions: lying and rolling, sitting, crawling and kneeling, standing, and walking, running, and jumping. Scores range from 0 to 100%, with higher scores indicating better gross motor function (better outcomes) and lower scores indicating poorer gross motor function (worse outcomes). Total scores and dimension scores will be used to evaluate motor performance and its association with gut microbiome characteristics.
Time frame: Baseline
Gastrointestinal Symptom Severity Score
Gastrointestinal symptoms, including constipation, diarrhea, abdominal pain, and bloating, will be assessed using a structured Gastrointestinal Symptom Questionnaire (total score range: 0-100, with higher scores indicating greater gastrointestinal symptom severity). Stool consistency will be assessed using the Bristol Stool Form Scale (BSFS), a 7-point scale ranging from Type 1 (separate hard lumps, indicating severe constipation) to Type 7 (entirely liquid stool, indicating severe diarrhea), with higher scores reflecting looser stool consistency.
Time frame: Baseline
Strengths and Difficulties Questionnaire Total Difficulties Score
Emotional and behavioral difficulties will be assessed using the Strengths and Difficulties Questionnaire (SDQ) Total Difficulties Score. The total difficulties score ranges from 0 to 40, with higher scores indicating greater emotional and behavioral difficulties (worse outcomes) and lower scores indicating fewer difficulties (better outcomes).
Time frame: Baseline
Patient-Reported Outcomes Measurement Information System Sleep Disturbance Scale Score
Sleep disturbance will be assessed using the Patient-Reported Outcomes Measurement Information System Sleep Disturbance Scale (PROMIS Sleep Disturbance Scale). The scale evaluates perceived sleep quality, sleep difficulties, sleep satisfaction, and sleep-related concerns. Scores range from 8 to 40, with higher scores indicating greater sleep disturbance (worse sleep outcomes) and lower scores indicating better sleep quality. Associations between sleep disturbance and gut microbiome characteristics will be examined.
Time frame: Baseline
Participation Questionnaire for Preschoolers With Autism Score
Participation will be assessed using the Participation Questionnaire for Preschoolers with Autism (PPA). The questionnaire evaluates participation in home, preschool, community, play, and social activities. The total score ranges from 0 to 100, with higher scores indicating greater participation in everyday activities (better outcomes) and lower scores indicating reduced participation. Associations between participation outcomes and gut microbiome characteristics will be examined.
Time frame: Baseline
Sensory Experiences Questionnaire Total Score
Sensory processing will be assessed using the Sensory Experiences Questionnaire Version 2.1 (SEQ-2.1), a caregiver-reported measure designed to evaluate sensory experiences in children with Autism Spectrum Disorder. The questionnaire assesses sensory hyperreactivity, hyporeactivity, and sensory-seeking behaviors across multiple sensory modalities. The total score ranges from 0 to 145, with higher scores indicating greater sensory processing difficulties (worse outcomes) and lower scores indicating fewer sensory processing difficulties. Associations between sensory processing outcomes and gut microbiome characteristics will be examined.
Time frame: Baseline
PROMIS Parent Proxy Cognitive Function Score
Cognitive functioning will be assessed using the Patient-Reported Outcomes Measurement Information System Parent Proxy Cognitive Function Measure (PROMIS Parent Proxy Cognitive Function Measure). The instrument evaluates caregiver-reported difficulties related to attention, memory, concentration, learning, and thinking abilities in children. Scores are reported as standardized T-scores (mean = 50, standard deviation = 10), with higher scores indicating better perceived cognitive functioning (better outcomes) and lower scores indicating poorer cognitive functioning (worse outcomes). Associations between cognitive function and gut microbiome characteristics will be examined.
Time frame: Baseline
Dietary Intake Score
Dietary intake will be assessed using parent proxy-reported 24-hour dietary recalls collected on 2-3 non-consecutive days, including at least one weekend day, using the multiple-pass recall method. Information on daily energy intake (kcal/day), macronutrient intake (g/day), dietary fiber intake (g/day), and consumption of key food groups (servings/day) will be recorded. A supplementary Food Frequency Questionnaire (FFQ) will assess the habitual consumption of fruits and vegetables, whole grains, fermented foods, sugar-sweetened beverages, and ultra-processed foods. Composite Healthy Diet Score and Unhealthy Diet Score will be derived to characterize dietary patterns, with higher Healthy Diet Scores indicating healthier dietary patterns and higher Unhealthy Diet Scores indicating less healthy dietary patterns. Dietary intake variables will be used as covariates in analyses examining associations between gut microbiome characteristics and neurodevelopmental functioning in children with
Time frame: Baseline
Pediatric Quality of Life Inventory Total Score
Quality of life will be assessed using the Pediatric Quality of Life Inventory (PedsQL). The instrument evaluates physical, emotional, social, and school functioning in children. Scores range from 0 to 100, with higher scores indicating better health-related quality of life (better outcomes) and lower scores indicating poorer health-related quality of life (worse outcomes). Associations between quality of life and gut microbiome characteristics will be examined in children with Autism Spectrum Disorder.
Time frame: Baseline
Anthropometric Nutritional Status Score
Anthropometric nutritional status will be assessed using standardized measurements of height (cm), weight (kg), and body mass index (BMI; kg/m²). Age- and sex-specific z-scores for weight-for-age, height-for-age, BMI-for-age, and weight-for-height (where applicable) will be calculated according to the World Health Organization (WHO) Child Growth Standards and Growth Reference charts. For z-score indicators, a value of 0 represents the WHO reference population median, positive values indicate measurements above the reference median, and negative values indicate measurements below the reference median. Nutritional status categories, including undernutrition, normal nutritional status, overweight, and obesity, will be determined using WHO classification criteria. Associations between anthropometric nutritional status and gut microbiome characteristics will be examined in children with Autism Spectrum Disorder.
Time frame: Baseline
Body Mass Index-for-Age Z-Score
Body mass index (BMI) will be calculated as weight (kg) divided by height squared (m²). BMI-for-age z-scores will be derived using World Health Organization (WHO) age- and sex-specific growth references. A z-score of 0 represents the WHO reference population median, positive z-scores indicate BMI values above the reference median, and negative z-scores indicate BMI values below the reference median. BMI-for-age z-scores will be used to evaluate nutritional status and examine their association with gut microbiome characteristics and neurodevelopmental functioning.
Time frame: Baseline
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