Americans overestimate how healthy they really are, according to a survey of 8,000 workers by Research Now and Aflac.

According to the 2012 Aflac WorkForces Report, 62 percent of workers said they do not think it’s likely they or a family member will be diagnosed with a serious illness such as cancer. More than half (55 percent) said they believe it is unlikely they will be diagnosed with a chronic illness, like heart disease or diabetes.

Compare these numbers to actual statistics, and the difference is staggering. While survey takers were right about diabetes—only 8.3 percent of Americans currently have the disease, according to the American Diabetes Assn.—they were wrong about everything else. One-third of women and one-half of men will be diagnosed with cancer at some point in their lives, according to the American Cancer Society. And about 1 in 6 U.S. deaths are caused by coronary heart disease every year, according to the American Heart Assn..

“The fact that American workers aren’t aware of their medical risks and the potential financial impact of those risks is a very real concern that is only compounded when workers don’t take full advantage of available benefits options or adjust their savings strategies to be more prepared,” said Audrey Boone Tillman, Aflac executive vice president of corporate services, in a press release.

And because so many Americans have a false sense of security, the study reveals, many are financially unprepared should they be diagnosed with a serious illness. The report found the following:

• Nearly 58 percent of American workers don’t have a financial plan to handle unexpected illnesses
• Only 8 percent strongly agree their family will be financially prepared in the event of an unexpected emergency
• About one-third have less than $500 in savings for emergency expenses.

The majority (57 percent) of respondents said they would need to tap into savings to pay for an unexpected illness, 30 percent would use a credit card, and 19 percent would have to withdraw funds from their 401(k) plans.

The report also showed a desire among Americans to increase their preparedness, though. Nearly 60 percent of workers said they would purchase voluntary health insurance plans—critical illness, short-term disability, or accident—if offered by their employer.