International children's accelerometry database (ICAD): design and methods

Area of Science:

• Pediatric physical activity research
• Objective measurement of physical activity
• Public health and epidemiology

Background:

• Accelerometers are increasingly used for objective physical activity measurement in children.
• Objective measures are more effective than subjective tools in detecting physical activity-health associations.
• The International Children's Accelerometry Database (ICAD) project standardized raw accelerometer data from global studies.

Purpose of the Study:

• To describe contributing studies to the ICAD project.
• To outline standardized methods for processing accelerometer data.
• To establish a novel data repository for future research on physical activity and health in children.

Main Methods:

• Collected 46,131 raw Actigraph data files from 20 international studies (2008-2010).
• Included anthropometric, demographic, and health data for children aged 3-18 years.
• Reduced data using standardized analytical methods.

Main Results:

• With wear time criteria of ≥ 8, ≥ 10, and ≥ 12 hours/day, 96%, 93.5%, and 86.2% of males, respectively, had valid data.
• Correspondingly, 96.3%, 93.7%, and 86% of females had at least one valid day of data.

Conclusions:

• Pooling accelerometer and phenotypic data increases statistical power and sample representativeness.
• Standardized methods optimize outcome variable generation and allow study of inter-study variability.
• Challenges include variability in accelerometry measurements and non-accelerometer data collection methods.