Walmart Inc. is in talks with health insurer Humana Inc. for a closer partnership to provide healthcare to consumers at home and prevent illness, according to a person familiar with the matter.

Healthcare spending accounted for about 18% of the U.S. economy last year, and continues to surge with an aging population, pricey medications and a complex regime of reimbursements and middlemen. Companies have been trying to address some of the market's inefficiencies by forging alliances or getting bigger: Cigna Corp. is acquiring Express Scripts Holding Co. for $54 billion, and CVS Health Corp. is buying Aetna Inc. for $68 billion.