Way behind were the many other password-protected staples of 21st century life: Personal contact information (24 percent), social media accounts (11 percent), Wi-Fi or internet log-in (10 percent), work email (4 percent) and online dating accounts (3 percent).

Vormetric responded to the survey by strongly urging people to consider the importance of protecting their medical records. It cited a recent study by the Ponemon Institute, a data security research group, that found that the average victim of medical data theft spent $13,500 to resolve the problem.

The FBI reports that medical data fetches a price many times higher than credit card data on the black market, Vormetric pointed out.

"Health care data sets contain extremely detailed personal information. Enough to not only apply for credit cards or loans, but also to generate huge sums from fraudulent medical charges," Tina Stewart, vice president of marketing for Vormetric, said in a statement. "The public's lack of awareness of their potential exposure to this is troubling. Few seem to realize that having their medical data lost is much more dangerous to their financial health than a stolen credit card number and address."

Hospitals and other medical providers have been a constant target of hackers in recent years. This summer UCLA Health, a major provider, reported that up to 4.5 million people may have had their data compromised by a cyberattack. 

Unfortunately, most Americans don't understand the most effective measures to protect against hacking. The survey found that 91 percent would still feel vulnerable if an encrypted file was stolen, even though encryption is the most effective way to keep data from being accessed.

"Essentially, it makes data totally inaccessible to those without the key required to decode it," Stewart said. "Without the key, encrypted data is meaningless to hackers, and when combined with strong access controls, encryption is one of the best tools available for safeguarding sensitive data in this environment."