What is the burden of establishing a disability in the context of medical malpractice?

In order to qualify for disability benefits, an applicant must show that: (1) he or she suffers from a medically determinable physical or mental impairment that can be expected to result in death, or that has lasted or can be expected to last for a continuous period of not less than twelve months; and (2) the impairment renders the applicant incapable of performing the work that he or she previously performed or any other substantially gainful employment that exists in the national economy. See 42 U.S.C. 423(d)(1)(A), (2)(A). An applicant must meet both requirements to be "disabled." Id. The applicant has the burden to establish disability. Terry v. Sullivan, 903 F.2d 1273, 1275 (9th Cir. 1990).