NEW YORK, Aug 6 (Reuters) - U.S. hospitals urged antitrust regulators this week to consider whether health insurer Anthem Inc's planned acquisition of rival Cigna Corp would boost healthcare costs. In a letter to the Department of Justice, the hospital industry's largest lobbying group said combining the No. 1 and No. 5 health insurers threatens to reduce competition in 817 geographic markets serving 45 million consumers. In many of those markets, the American Hospital Association said, there are no strong competitors to buy assets that Anthem or Cigna might want to sell to pass muster with federal authorities. State insurance regulators will also look at the deal. A Cigna spokesman did not have an immediate comment. An Anthem spokeswoman also did not have an immediate... More