Protecting Older Workers Against Discrimination Act (Sec. 2) This bill amends the Age Discrimination in Employment Act of 1967 to establish as an unlawful employment practice that age or participation in investigations, proceedings, or litigation under such Act were a motivating factor for any unlawful employment practice, even though other factors also motivated the practice (thereby allowing what are commonly known as mixed motive claims). The bill (1) permits a complaining party to rely on any type or form of admissible evidence, which need only be sufficient for a reasonable trier of fact to find that an unlawful practice occurred; and (2) declares that a complaining party shall not be required to demonstrate that age or retaliation was the sole cause of the employment practice (thereby rejecting the Supreme Court's decision in Gross v. FBL Financial Services, Inc. , which requires a complainant to prove that age was the but-for cause for the employer's decision). The bill authorizes a court to grant declaratory and injunctive relief, but prohibits a court from awarding damages or issuing an order requiring any admission, reinstatement, hiring, promotion, or payment. The bill applies the same standard of proof to other employment discrimination and retaliation claims, including claims under the Civil Rights Act of 1964, the Americans With Disabilities Act of 1990, and the Rehabilitation Act of 1973. (Sec. 5) The Government Accountability Office shall report on how the Equal Employment Opportunity Commission (EEOC) investigates mixed motive age discrimination claims arising under all such Acts amended by this bill. (Sec. 6) The Department of Labor and the EEOC shall jointly conduct a study to determine the number of claims pending or filed, in addition to cases closed, by women who may have been adversely impacted by age discrimination as a motivating factor in workplace discrimination or employment termination. (Sec. 7). The EEOC, for a five-year period, shall submit to Congress a report at one-year intervals on the number of age discrimination in employment claims brought under this bill. (Sec. 8) The EEOC shall report on the status of federal mixed motive age discrimination in employment claims made against federal agencies.