by Phyllis Hanlon, Contributing Writer

According to a statement from the American Heart Association (www.heart.org) and published in the medical journal Circulation, (http://circ.ahajournals.org/content/96/9/3248) obesity has been associated with several other medical conditions, including heart disease. But an unusual phenomenon called the “obesity paradox” is when obese people with certain cardiovascular disorders are found to have better survival than those who are non-obese. A recent research project looked at the impact of obesity on outcomes for patients with WHO Group 1 PH (PAH, pulmonary arterial hypertension) (https://www.ncbi.nlm.nih.gov/pubmed/28601194)

This study pulled data from the National Inpatient Sample (NIS) (https://www.hcup-us.ahrq.gov/nisoverview.jsp) database for the years 2003 to 2011 on patients over the age of 18 who were admitted to the hospital with a primary (or first) diagnosis of PAH (the diagnosis that led to hospitalization). They then classified whether or not the patients were likely to be obese based on additional diagnosis billing codes. The researchers wanted to look at how many patients with PAH and obesity had died while in the hospital compared to their non-obese counterparts.

Manyoo Agarwal, M.D., and colleagues explained that the NIS provides a wealth of information on patients admitted to the hospital, including patient demographics, characteristics related to the hospitalization, insurance status, other medical conditions, length and cost of hospital stay and result of the hospitalization.

A total of 18,450 patients met the researchers’ criteria. Since obesity has been shown in other studies to have negative effects on heart and lung functioning, the researchers expected that obese PAH patients would have worse survival compared to non-obese PAH patients. However, their analysis found that obese PAH patients had a mortality of 3.5 percent while hospitalized versus 8.1 percent for non-obese PAH patients in the hospital. This difference remained statistically significant even after ensuring the researchers compared obese/non-obese PAH patients of similar demographics, hospital characteristics, and clinical co-morbidities. They attributed the results to the “obesity paradox.” And several other studies support their conclusion.

A 2013 study examining the effects of obesity in pulmonary hypertension (PH) patients found that obese PH patients had better survival than non-obese patients in the study when followed for an average of about 1.5 years. (http://www.resmedjournal.com/article/S0954-6111(12)00404-0/fulltext) A second study reported a observed reduction in the ten-year mortality for those with a high body mass index (BMI) who had been taking subcutaneous (i.e., under the skin) treprostinil (Remodulin®) (http://www.jhltonline.org/article/S1053-2498(11)00873-4/fulltext).

While researchers have no specific explanation for the “obesity paradox,” some have offered speculation. One theory as to why PAH, or certain other cardiovascular or pulmonary disease, patients who are obese seem to have better survival could relate to a protective effect from excess fat tissue. Excessive adipose tissue (i.e., fat) could serve as a buffer between the proteins that affect interaction and communication between cells. Other researchers believe that patients who are obese might see a physician earlier due to worse symptoms of their condition; other medical problems could be revealed during visits, leading to earlier treatment.

Although this study provides further evidence of an “obesity paradox” in PAH patients, it had several limitations. First, the definitions of obesity and PAH were based on a coding system, ICD-9, so the researchers could not confirm these with body mass index or clinical variables, and PAH may have been misclassified. Also, obesity is underreported in the NIS database compared with other nation-wide surveys. Finally, information on medications, physical activity, exercise or fitness were unavailable.

In spite of the results of this study, the authors caution that weight gain in those who are not obese should not be encouraged. Rather, this “obesity paradox” should foster more research to find out the underlying factors behind this phenomenon and use the information to improve patient care and outcomes.

Each PH patient is different. It is essential that you talk to your own doctor about what treatment options are best for you. For more information on finding a doctor or an accredited care center, visit https://www.phassociation.org/PHCareCenters/Patients.