limb). The small research literature on disability and environmental factors reflects this.

For the 2005 IOM workshop on disability in America, Keysor (2006) summarized the ICF and other taxonomies of the environment, described instruments for measuring the relationship between the environment and disability, and reviewed research on how the environment influences disability. She found a limited amount of research, especially prospective, controlled studies, that directly evaluated people’s functioning and participation in the community. Of the studies that she identified, most involved mobility limitations and the built environment (e.g., buildings and pedestrian spaces).

In her review, Keysor pointed to evidence suggesting “that some environments that are more facilitative are associated with less disability, whereas other environments that are facilitative are associated with more disability” (Keysor, 2006, p. 98). This seeming paradox may reflect a complex and dynamic process of human adaptation to or modification of the environment. For example, people with greater levels of physical impairment and more difficulty getting around may modify their environments to reduce barriers and make life easier; they may also choose their home or work environment, or both, to minimize barriers. Studies that can untangle such causal relationships are important but difficult.

In general, research has tended to examine how or whether people perceive environmental features as barriers and has less often attempted to observe directly the effects of environmental features on such outcomes as functioning, social participation, and costs. Assessments of interventions to modify the environment are uncommon. A few controlled studies have evaluated home modifications (see e.g., Mann et al. [1999], Gitlin [1995], and Gitlin et al. [2006]). Each of these types of research is important, although some strategies are more difficult to design and implement than others. Assessing people’s perceptions of the effects of environmental barriers on activities and participation is usually easier and less expensive than directly measuring the effects of environmental features on these outcomes and, especially, undertaking controlled studies of interventions to modify these features. The final section of this chapter includes recommendations about directions for further research on environmental factors.

Reis et al. (2004, p. 2)