Keith Speights

The Motley Fool

Americans include two health-related issues among the 10 most important problems facing the U.S., according to a recent Gallup survey. Healthcare in general ranked fourth on the list, with Ebola coming in at no. 8. But is Ebola really among the biggest health problems for Americans? Not when we look at the chances of actually being infected.

So, what are the actual biggest health problems that Americans face? One way to answer this question is to look at what drugs are prescribed the most. Here are the seven top health problems based on the most-prescribed drugs in the U.S., according to Medscape's analysis of data provided by IMS Health.

1. Hypothyroidism

AbbVie's (ABBV) Synthroid ranks at the top of the list of most-prescribed drugs. Synthroid is used to treat hypothyroidism, a condition caused by an underactive thyroid gland.

The American Thyroid Association estimates that 2%-3% of Americans have pronounced hypothyroidism, while 10%-15% have a mild version of the disease. Hypothyroidism occurs more frequently in women, especially women over age 60. Around half of Americans with the condition don't realize that they have hypothyroidism.

2. High cholesterol and high triglycerides

Coming in at a close second on the list is AstraZeneca's (AZN ) Crestor. The drug is used to help control high cholesterol and high triglyceride levels.

According to the American Heart Association, nearly 99 million Americans age 20 and over have high cholesterol. Elevated cholesterol levels are one of the major risk factors for heart attacks and strokes. The problem is that you won't know if you have high cholesterol unless you get tested -- and around one in three Americans haven't had their cholesterol levels checked in the last five years.

3. Heartburn and gastroesophageal reflux disease

AstraZeneca also claims the third most prescribed drug in the nation -- Nexium. The "purple pill" helps treat hearburn and gastroesophageal reflux disease, or GERD, also commonly referred to as acid reflux.

Around 20% of Americans have GERD, according to the American Society for Gastrointestinal Endoscopy. A lot of people take over-the-counter medications, but that's not enough for many others. Medscape reported that over 18.6 million prescriptions of Nexium were filled between July 2013 and June 2014.

4. Breathing disorders

The next two highly prescribed drugs treat breathing disorders. GlaxoSmithKline's (GSK ) Ventolin HFA is used by asthma patients, while the company's Advair Diskus treats asthma and chronic obstructive pulmonary disease, or COPD.

More than 25 million Americans have asthma. Around 7 million of these patients are children. Meanwhile, COPD, which includes chronic bronchitis and emphysema, ranks as the third-leading cause of death in the U.S.

5. High blood pressure

Novartis (NVS) claims the next top-prescribed drug with Diovan. The drug treats high blood pressure by relaxing and widening blood vessels, thereby allowing blood to flow more readily.

Around one-third of American adults have high blood pressure. Many don't know that they are affected, because the condition doesn't usually manifest symptoms for a long time. However, high blood pressure can eventually lead to other serious health issues, including heart and kidney problems.

6. Diabetes

Several highly prescribed drugs combat diabetes, with Sanofi's (SNY) Lantus Solostar taking the top spot for the condition. Lantus Solostar is a long-acting basal insulin that is used for type 1 and type 2 diabetes mellitus.

According to the National Diabetes Statistics Report released in June 2014, 29.1 million Americans had diabetes in 2012. That's a big jump from just two years earlier, when 25.8 million Americans had the disease. Diabetes ranks as the seventh leading cause of death in the U.S.

7. Depression and anxiety

Eli Lilly's (LLY) Cymbalta fell just below Lantus Solostar in number of prescriptions. Cymbalta is the leading treatment for depression and generalized anxiety disorder.

The Anxiety and Depression Association of America estimates that 14.8 million Americans ages 18 and older suffer from a major depressive disorder each year. Around 3.3 million have persistent depressive disorder, a form of depression that lasts for two or more years. Generalized anxiety disorder affects around 6.8 million adults in the U.S.

Common thread for common diseases

One thing that stands out about several of these common diseases affecting millions of Americans is that many people have one or more of these conditions -- but don't know it. This underscores the importance of getting a checkup on a regular basis.

Regardless of what the Gallup survey found, the odds of you getting Ebola are very low. On the other hand, the chances of you or someone in your family already having one of these seven conditions could be higher than you might think. Perhaps the truly biggest healthcare challenge facing Americans is knowing the status of their own health.

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