Impairment, Disability, and Participation
Quantifying the impacts of LDD and their preventive interventions is complicated by the fact that these disorders can exist and be measured at multiple levels, including three levels distinguished by the World Health Organization (WHO) in International Classification of Functioning, Disability, and Health (WHO 2001):
-
impairment, which refers to physiological or psychological defects or abnormalities, such as failure of the neural tube to close
-
function or disability, which refers to the ability of an individual to perform a task, such as walking, seeing, hearing, learning language, and reading
-
participation, which refers to the degree to which an individual participates in school, employment, social role, and recreational activities.
A given impairment may be associated with a range of functional outcomes. Some but not all of these may be recognized as disability. Disability is context specific and may vary from culture to culture. For example, conditions such as dyslexia, attention deficit and hyperactivity disorder (ADHD), and mild MR may be especially disabling in school but not as noticeable in nonacademic settings and environments where schooling is optional. Environmental factors and social stigma may determine the participation of people with disabilities more than do the functional deficits themselves. Some interventions may be designed to enhance participation (for example, ramps, accessible public toilets, inclusive education), whereas others may target impairment and disability (for example, nutritional fortification, surgery, rehabilitation, special education, newborn screening, and early treatment).
