This New York Times article from 1998 profiles one man caring for his elderly mother and explores the culturally specific commitment to family-provided elder care, as well as discussing probably historical roots.
A cross sectional survey of 600 middle-aged black and white adults with both children and aging parents found that although both races felt obliged to help their parents, black adults tended to provide greater support to their elders. The study published in 2010 in The Gerontologist concludes that the reported sense of obligation to parents is what explained the difference.