The North American life insurance industry generally enjoys strong balance sheets and improving earnings, says Fitch Ratings in a new report.

The rating agency issued a report on the U.S. and Canadian life insurance companies, which finds that the industry is continuing to maintain balance sheet strength and improved debt-servicing capacity.

Generally, life insurers’ operating earnings improved modestly through 2014, Fitch says; and, it notes that their operating-based coverage metrics improved, too. “Continued run-up in equity market valuations, if sustained, and an uptick in interest rates would be primary drivers of further improvements in coverage,” it says.

However, in the longer term, Fitch says that it believes life insurers “face an uphill battle to materially improve operating earnings-based interest coverage metrics due to a continuation of historically low interest rates and uncertainty tied to market returns.”

Additionally, it says that a rapid uptick in interest rates could have a more immediate impact on capital and liquidity.