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Year : 2022  |  Volume : 25  |  Issue : 6  |  Page : 1181-1182

Parkinson's disease: The dirty truth about the air – Authors' reply

1 Department of Neurology, Tokyo Metropolitan Neurological Hospital, 2-6-1 Musashidai, Fuchu, Tokyo, 183-0042, Japan
2 Department of Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-higashi, Kodaira, Tokyo, Japan

Date of Submission01-Nov-2022
Date of Acceptance02-Nov-2022
Date of Web Publication22-Nov-2022

Correspondence Address:
Hidehiro Mizusawa
Department of Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawa-Higashi, Kodaira, Tokyo 187-8551
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/aian.aian_878_22

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How to cite this article:
Saitoh Y, Mizusawa H. Parkinson's disease: The dirty truth about the air – Authors' reply. Ann Indian Acad Neurol 2022;25:1181-2

How to cite this URL:
Saitoh Y, Mizusawa H. Parkinson's disease: The dirty truth about the air – Authors' reply. Ann Indian Acad Neurol [serial online] 2022 [cited 2023 Jan 29];25:1181-2. Available from:

Dear Editor,

We thank the readers, Dr. Scorza and colleagues, for their interest in our recent work entitled “Current evidence for the association between air pollution and Parkinson's disease”.[1] In their comment, they raised an important issue regarding the relationship between air pollution and cardiovascular dysfunction in Parkinson's disease (PD) that may cause a clinical entity called sudden and unexpected death in PD (SUDPAR). Bäckström et al.[2] reported that cardiovascular disease was a common cause of death in PD patients, even though the most common cause was pneumonia. As Dr. Scorza and colleagues mentioned, the cause of SUDPAR is still unknown but a cardiac dysfunction such as fatal arrhythmia or coronary heart disease could be one of its causes. Considering air pollutants usually penetrate the lung and cardiovascular system via respiration, we agree that air pollution could be associated with SUDPAR through the deterioration of cardiovascular dysfunction. Recent evidence by Jin et al.[3] indicated that long-term exposure to various air pollutants was associated with the incidence of cardiovascular diseases, even at low pollutant concentration levels. Park et al.[4] conducted a nationwide, population-based cohort study that revealed that PD was associated with a higher risk of developing cardiovascular diseases. However, conflicting evidence regarding the association between PD and the risk of cardiovascular events exists. Alves et al.[5] reported a meta-analysis on the topic that the risk of cardiovascular events was not different in PD and non-PD patients. Additionally, Posada et al.[6] also reported that cardiovascular diseases were the most frequent cause of death in PD patients, which was similar to the general population. Interestingly, Nishida et al.[7] reported two cases of sudden unexpected death in elderly individuals in whom post-mortem examination revealed early changes of Lewy pathology. They identified Lewy pathology in the heart and peripheral autonomic nervous systems, implying that autonomic dysregulation could be a risk of sudden unexpected death,[7] whereas many cases of incidental Lewy bodies without sudden death were reported.[8]

Although some literature showed a positive association between air pollution and mortality in PD patients, we did not find the specific cause of death in our review.[1] We would like to briefly emphasize the several difficulties in analyzing the specific cause of death in the large cohort study. First, multimorbidity is common in elderly persons. Most of the population over the age of 65 years were multimorbid, and the number of chronic disorders increased with age.[9] This multimorbidity could be eventually the cause of SUDPAR. Second, it is difficult to prove the real cause of SUDPAR because it occurs “suddenly” and “unexpectedly”. If PD patients died from coronary artery disease, cerebrovascular disease, and pulmonary embolism, those are common causes of sudden death, then the post-mortem examination could identify abnormalities in the involved organs. However, in PD patients who died from some fatal arrhythmia, post-mortem examination could not identify the abnormalities of the cardiac anatomy.

Indeed on rare occasions, we encounter some PD patients who died suddenly, even though their stage of PD was not advanced. Therefore, prospective studies adjusted for potentially confounding factors we mentioned in the literature[1] and in this letter are warranted to elucidate the impact of air pollution on cardiovascular dysfunction in PD patients and SUDPAR. As we stated in our recent work,[1] we also highlight that policymakers of both developing and industrialized countries should collaborate to reduce air pollution and prevent overall health problems. Once again, we thank Dr. Scorza and colleagues for their insightful comments and discussions.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Saitoh Y, Mizusawa H. Current evidence for the association between air pollution and Parkinson's disease. Ann Indian Acad Neurol 2022;25:S41-6.  Back to cited text no. 1
Bäckström D, Granåsen G, Domellöf ME, Linder J, Jakobson Mo S, Riklund K, et al. Early predictors of mortality in parkinsonism and Parkinson disease: A population-based study. Neurology 2018;91:e2045-56.  Back to cited text no. 2
Jin T, Di Q, Réquia WJ, Danesh Yazdi M, Castro E, Ma T, et al. Associations between long-term air pollution exposure and the incidence of cardiovascular diseases among American older adults. Environ Int 2022;170:107594.  Back to cited text no. 3
Park JH, Kim DH, Park YG, Kwon DY, Choi M, Jung JH, et al. Association of parkinson disease with risk of cardiovascular disease and all-cause mortality: A nationwide, population-based cohort study. Circulation 2020;141:1205-7.  Back to cited text no. 4
Alves M, Pita Lobo P, Kauppila LA, Rebordao L, Cruz MM, Soares F, et al. Cardiovascular and cerebrovascular risk markers in Parkinson's disease: Results from a case-control study. Eur J Neurol 2021;28:2669-79.  Back to cited text no. 5
Posada IJ, Benito-Leon J, Louis ED, Trincado R, Villarejo A, Medrano MJ, et al. Mortality from Parkinson's disease: A population-based prospective study (NEDICES). Mov Disord 2011;26:2522-9.  Back to cited text no. 6
Nishida N, Yoshida K, Hata Y. Sudden unexpected death in early Parkinson's disease: Neurogenic or cardiac death? Cardiovasc Pathol 2017;30:19-22.  Back to cited text no. 7
Miki Y, Mori F, Wakabayashi K, Kuroda N, Orimo S. Incidental Lewy body disease restricted to the heart and stellate ganglia. Mov Disord 2009;24:2299-301.  Back to cited text no. 8
Barnett K, Mercer SW, Norbury M, Watt G, Wyke S, Guthrie B. Epidemiology of multimorbidity and implications for health care, research, and medical education: A cross-sectional study. Lancet 2012;380:37-43.  Back to cited text no. 9


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