Health insurance providers have a long history of telling individual policyholders — and people shopping for individual policies — that their care isn’t covered or their policy is voided because of a pre-existing condition. Starting in 2014, that is all supposed to stop when a condition of the Affordable Care Act kicks in, making it illegal for health insurers in the individual market to deny coverage, increase premiums, or restrict benefits because of a pre-existing condition. Question is: Just how many people are we talking about?

That’s why the federal calculator-heads at the Government Accountability Office recently undertook a study to look at which pre-existing conditions could put people on insurance providers’ Have Fun Paying The Hospital Bill Yourself List (a name we just made up but which we would not be shocked to find out is accurate), and what that means in terms of the U.S. population.

Since there is no set list of pre-existing conditions for which insurers will deny coverage, GAO rounded up those conditions that are most frequently associated with denied coverage, increased premiums or restricted benefits.

Topping that list is hypertension, which afflicts more than 33 million Americans between the ages of 19-64. That was followed by mental health disorders, diabetes, asthma, arthritis, COPD, cancer (excluding skin cancer). rheumatoid arthritis, heart attack, and stroke.

GAO then looked at five separate studies to estimate the possible range of Americans who have had a condition (not just limited to the above list) that could prevent them from receiving proper coverage.

Because each study looked at a different number of possible high-risk conditions, those studies demonstrate a wide range of results. On the low end, a study that only asked people about eight different pre-existing conditions comes up with an estimate of around 36 million people. Another study asked about more than 60 conditions and came up with 60 million affected Americans. Finally, the study that resulted in an estimate of 122 million people looked at 417 separate conditions considered to be chronic.

Of interest is that all the studies found that women are more likely to have a pre-existing condition, with anywhere from 21% to 72% of the female population affected (the midpoint is 37%). Meanwhile, 18% to 59% of males (28% midpoint value) may have a condition the insurance companies shake their heads at.

We doubt it will shock may people that the rate of pre-existing conditions also goes up dramatically once people hit their mid-50s. Between the ages of 55-64, anywhere from 43% to 84% of people (48% midpoint) are believed to have a chronic condition, a big increase over the 23% to 72% (midpoint 37%) range for people ages 45 to 54.

GAO notes that the groups reporting the lowest level of pre-existing conditions, are those who have individual insurance policies and those without any health insurance.

The report explains:

The lower reporting of pre-existing conditions among the uninsured, in part, may reflect the fact that they are less likely than the insured to receive timely preventive care and some common health problems such as hypertension and diabetes often go undetected without routine checkups. In addition, the uninsured are also less likely to have regular preventive care, including cancer screenings.

The lower reporting of pre-existing conditions among those with private individual insurance may be a reflection of the fact that insurers try to limit the number of people with pre-existing conditions that they accept into their plan.

You can expect these numbers to come into play by both sides of the health care debate. Defenders of the Affordable Care Act will likely say the data shows the sheer number of people who are going out-of-pocket (or not getting the care they need) if insurers are allowed to continue denying coverage for pre-existing conditions. Meanwhile, insurance companies can likewise point to the GAO study and use it to justify such policies, as they can not be expected to cover so many millions of unprofitable policyholders.

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