Yes, in most states you can, within limits. Federal rules allow insurers to charge older adults (e.g., in their sixties) up to three times the premium they would charge younger adults (e.g., in their early twenties).
This limit on age rating applies to all non-group and small-group health insurance policies, whether sold in the Marketplace or outside of the Marketplace. 
Some states prohibit insurers from adjusting premiums for age, or limit the age adjustment to less than three-to-one.
Source: KFF
