"We were shocked to find such high rates of hardship among upper-income families," lead investigator Susan L. Parish of the University of North Carolina at Chapel Hill School of Social Work said in a statement.

The study is based on 2002 data from the National Survey of American Families that analyzed 28,141 households.

The study, published in the journal Exceptional Children, finds families across all income levels raising disabled children are significantly more challenged by food, housing and health issues compared to families without disabled children. Many struggled to pay their bills.

The data indicated that a significant percentage of those struggling are higher-income households but federal poverty guidelines, which have remained unchanged since the 1960s, are used to determine eligibility for many income, food, health and disability-related programs. In 2002, the federal poverty level for a family of four was $18,100.

Forty percent of the surveyed families with disabled children earning $36,200 to $54,300 for a family of four experienced at least one food hardship.