People with Parkinson’s disease might want to pay extra attention to that cough or chest pain. A large retrospective U.S. study, appearing online January 2 in the Archives of Neurology, reports—perhaps not surprisingly—that elderly people with PD have a greatly increased risk of dying compared to seniors without the condition. Of particular note, however, death is frequently associated with complications such as infection, cardiovascular disease, and dementia, some of which may be preventable. The researchers, led by Allison Willis and Brad Racette at Washington University School of Medicine, St. Louis, Missouri, also found hints that exposure to environmental toxins could hasten decline in PD patients. The results point to the importance of screening people with PD for other health conditions, and to the need for more research on the effect of environmental exposures on the disease course, Willis told ARF.

To investigate factors affecting survival in PD, Willis and colleagues searched nationwide Medicare claims data from 2002, identifying more than 138,000 Americans with PD whom they followed through 2008. This represents the largest such cohort studied to date and, since Medicare is used by nearly all Americans 65 or older, the sample should reflect the general population, the authors note. The six-year death rate for people with PD was almost four times higher than that in the general elderly population. Notably, the PD death rate equated to that seen for heart attacks, Alzheimer’s disease, and hip fractures. (Hip fractures are particularly devastating for elderly people due to the associated complications and loss of mobility.) The PD death risk was slightly lower in women, Asians, and Hispanics compared to white and African American men.

Having dementia nearly doubled the death risk. About 70 percent of the PD patients in the study had dementia, compared to a nationwide dementia prevalence of around 15 percent for people over 70 (see Plassman et al., 2007). Previous estimates of dementia prevalence in PD had varied from about 25 to 90 percent. Parkinson’s disease frequently progresses to Parkinson’s dementia (see, e.g., ARF related news story), but people with PD may also get other dementias such as AD or vascular dementia. Although the Medicare data does not distinguish dementia type, in this cohort more women and African Americans were diagnosed than other groups, mirroring AD demographics and suggesting that at least some of the cases might be due to AD, the authors observe. The finding highlights the importance of screening for dementia in people with PD and taking preventive measures, Willis said. For example, undertreated heart disease could lead to vascular dementia.

Additionally, the authors found that PD patients living in urban areas with high industrial manganese output had about 20 percent higher death risk than those in low-manganese counties. In a previous study, Racette’s group reported abnormalities in the dopaminergic system in welders, who are occupationally exposed to manganese (see ARF related news story on Criswell et al., 2011), implying the metal could be a risk factor for PD. “We should probably start thinking about how environmental exposures to all kinds of pollutants can affect disease progression,” Willis said. In ongoing work, she is setting up a large prospective study that will collect data on several types of pollution exposure in PD patients and correlate this with disease progression.

“The good thing about these types of studies is that they generate a lot of questions,” said Jane Ann Driver at Brigham and Women’s Hospital, Boston, Massachusetts. She was not involved in the study. Driver is particularly intrigued by the link to manganese toxicity. “We don’t know what causes most cases of PD, so anything that sheds light on a risk that hasn’t been appreciated before, and is potentially reversible, is important.”

Driver noted that, because PD affects so many aspects of health (see, e.g., ARF related news story), it makes sense that people with the disease are more susceptible to infections and other complications. The study raises the question of whether cardiovascular problems are underdiagnosed or undertreated in PD patients, Driver said. For their part, the authors speculate that symptoms of heart trouble such as fatigue or weakness could be mistaken for PD symptoms and overlooked. Willis suggested that people with Parkinson’s may need extra time with their physician to make sure their basic health is being managed as well as possible.—Madolyn Bowman Rogers

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  1. This study by Willis et al. is highly informative about demographics and life expectancy in Parkinson's disease. The main findings are that life expectancy is shorter than might have been reported before, and that dementia is very common and is a significant contributor to mortality risk.

    Previous estimates of dementia in PD have ranged from 25-75 percent (Buter et al., 2008; Emre, 2003; and others). The current report suggests it is closer to the 75 percent estimate. Also, this study now gives an estimate of how much dementia contributes to mortality. In fact, it appears that dementia is a leading contributor to mortality in PD. It has been reported by us and others that cognitive and functional decline are related in PD, and that cognitive decline is a risk factor for functional decline, but how it contributed to mortality had not been reported.

    The study has a PD population that is older than other PD cohorts. The average onset is age 60, and the mean age is around 67. This cohort has a mean age (estimated, not reported) of around 75. The age might contribute to a shortened life expectancy and an increase risk of dementia. Parkinson's disease dementia (PDD) seems to have many etiologies. Our group previously reported that AD pathology represents about half of PDD. This report represents around two-thirds. AD is well known to be associated with an increased risk of mortality.

    References:

    . Dementia and survival in Parkinson disease: a 12-year population study. Neurology. 2008 Mar 25;70(13):1017-22. PubMed.

    . Dementia associated with Parkinson's disease. Lancet Neurol. 2003 Apr;2(4):229-37. PubMed.

    View all comments by Marwan Sabbagh

References

News Citations

  1. Barcelona: Taking Parkinson’s Research From Movement to Mind
  2. Is Manganese a Risk Factor for PD?
  3. Parkinson’s: Thinking Outside the Brain’s Black Box

Paper Citations

  1. . Prevalence of dementia in the United States: the aging, demographics, and memory study. Neuroepidemiology. 2007;29(1-2):125-32. PubMed.
  2. . Reduced uptake of [¹⁸F]FDOPA PET in asymptomatic welders with occupational manganese exposure. Neurology. 2011 Apr 12;76(15):1296-301. PubMed.

Further Reading

Primary Papers

  1. . Predictors of Survival in Patients With Parkinson Disease. Arch Neurol. 2012 Jan 2; PubMed.