The likely SSI cut will affect not just younger adults with disabilities such as Down syndrome and severe autism who are still living at home with their low-income parents, but also older people with health or financial problems who have had to move in with their adult children on tight budgets. All told, as many as 400,000 poor and disabled people and indigent older people across the United States could have their support cut or eliminated, according to a ProPublica analysis of actuarial figures from the Social Security Administration. Supplemental Security Income, which serves 7.5 million Americans who are unable to make a living because of severe disabilities or destitution in old age, has never been easy to qualify for. Fewer than a third of applicants are approved, and the process often takes years.