LifePlans Inc. has picked John Hancock Life Insurance Company to help with a study on ways to improve older Americans’ health.

Researchers at LifePlans, Waltham, Mass., will be working with Hancock, Boston, a unit of Manulife Financial Corp., Toronto, to develop and test strategies for keeping older people from falling.

Researchers estimate fall injuries involving Americans ages 65 and older cost the country about $35 billion per year, Hancock says.

The U.S. Department of Health and Human Services hired LifePlans to conduct fall prevention research in an effort to improve older Americans’ lives and reduce the amount of federal and state dollars going to treat fall injuries.

The 5,000 Hancock policyholders who choose to participate in the study will get telephone evaluations conducted by nurses; an in-home visit by a nurse, to look for conditions that might contribute to a fall; a personalized fall-reduction action plan; and a fall prevention tool kit, including a pedometer and an exercise video.