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Predicting Survival in People with Parkinsonís

Certain demographic and clinical factors can influence survival of people with Parkinson’s disease (PD), according to a report in the January issue of the Archives of Neurology. In particular, people with dementia were significantly less likely to survive over a six-year period.

Some previous studies suggested that people with Parkinson’s disease have a higher risk of death than the general population, but other studies found no such difference. It is possible that different groups of people with Parkinson’s have different life expectancies, leading to these conflicting results.

To identify demographic, geographic, and clinical factors that may influence survival of people with Parkinson’s, Allison Willis, M.D., and her colleagues at the Washington University School of Medicine examined the health records of over 29 million Medicare beneficiaries with Parkinson’s. They identified 138,000 individuals who were diagnosed with Parkinson’s in 2002 and followed their medical charts through 2008. Dr. Willis and her coworkers gleaned data such as demographics, health service use, and survival from Medicare Beneficiary Annual Summary Files. Then they compared six-year survival rates among different groups of people with Parkinson’s.

Results

  • 64 percent of people with Parkinson’s died during the six-year study.
  • Sex and race significantly predicted survival. Women with Parkinson’s had a 26 percent lower adjusted risk of death than men. African-Americans had the highest crude death rate (66.4 percent), followed by whites (64.6 percent), Hispanics (55.4 percent), and Asians (50.8 percent).
  • 69.9 percent of the people with Parkinson’s developed dementia by the end of the six-year study. People with dementia had a higher death rate (71.9 percent) than those without dementia (46.1 percent).
  • Survival rates were similar across the United States – across states, regions of the country, and rural/urban classifications. However, people with Parkinson's living in urban areas where high levels of manganese were released into the environment had a modestly increased death risk.
  • After adjusting the data for age, race, and sex, people with Parkinson’s had a nearly four times greater risk of death than people with no disease and nearly double the risk of death than for those living with other common diseases such as colorectal cancer, stroke and ischemic heart disease.  People with Parkinson’s had nearly the same risk of death as those who had experienced a heart attack or suffered a hip fracture.

 

What Does It Mean?

These findings suggest that Parkinson’s is associated with a reduced life expectancy compared with no disease or with other diseases common in elderly people. Dementia, which is common among people age 65 and over, had the strongest effect on age-adjusted survival among the variables studied. Women, Hispanics, or Asians had a lower risk of death than white men. The study provides some of the first evidence that environmental factors, such as industrial manganese output, may influence risk of death after Parkinson’s diagnosis.

One strength of this study is its large sample population, which included groups such as women and minorities that are often underrepresented in these types of studies. This study also has some limitations. One is that the study relied entirely upon diagnosis codes, which were not validated with spot checks. Diagnoses are recorded on a person’s medical records, and thus can be helpful in assessing who has Parkinson’s. But there is room for error. For instance, both the diagnosis of Parkinson’s itself as well as predictors of mortality like dementia may be under-diagnosed or over-diagnosed in selected populations. Nevertheless, these results are consistent with those seen in other, smaller studies.

In summary, this study highlights the fact that a PD diagnosis likely affects life span; and, among people affected by PD, dementia is a predictor of a shorter life span. As a significant non-motor feature of Parkinson’s disease, it is clear that additional research is needed to develop ways to diagnose and treat cognitive impairment in PD.


Reference: Allison W. Willis; Mario Schootman; Nathan Kung; Bradley A. Evanoff; Joel S. Perlmutter; Brad A. Racette, Predictors of Survival in Patients With Parkinson Disease, Arch Neurol. 2012; Published online January 2, 2012. http://dx.doi.org/10.1001/archneurol.2011.2370

Source Date: Jan 04 2012