National Death Index

National Death Index (NDI) is a United States resource available to researchers from the USA National Center for Health Statistics to obtain death status (regular NDI) or cause of death (NDI Plus) for deaths of USA citizens occurring within the USA. National Death Index (NDI) is a United States resource available to researchers from the USA National Center for Health Statistics to obtain death status (regular NDI) or cause of death (NDI Plus) for deaths of USA citizens occurring within the USA.