Epidemiological approaches to the etiology of Parkinson's disease

A predictive model of neurodegeneration in idiopathic REM-sleep behavior disorder

OBJECTIVE

To investigate whether Parkinson's disease (PD) and dementia are competing risks in subjects with idiopathic rapid-eye-movement sleep behavior disorder (RBD).

METHODS

The number of incidental PD cases observed in 11 longitudinal RBD studies was compared with the corresponding expected number as estimated by a simple mathematical model based on population parameters for PD age-of-onset.

RESULTS

The expected number of incidental PD cases exceeded observed PD cases (p-value < 0.001) but was in agreement with the sum of observed PD cases and observed mild cognitive impairment/dementia cases (p-value = 0.34). Sensitivity analyses confirmed the results.

CONCLUSION

In the RBD population, PD and dementia cases are competing risks, suggesting that alpha-synuclein pathology occurs simultaneously in substantia nigra and neocortex. This observation has implications for the design and analysis of trials of neuroprotection.

Evidence for environmental causation of Parkinson's disease

To address the question of whether Parkinson's disease (PD) is a genetic or an environmental disorder; (i) we modeled the hazard of PD using two-parameter hazard functions; and (ii) we investigated whether the hazard rate of index cases depended on the age of symptom onset in the affected parent (genetic model) or depended on the age of the index case at the time the affected parent developed PD (environmental model). We found that the hazard of PD increased monotonically with age according to a Weibull function. The risk associated with the presence of maternal PD did not depend on the age of onset of the affected mother but on the child's age at the time, the affected mother developed symptoms. The younger the child when the mother began to have symptoms, the higher the risk for the child. When the affected parent was the father, both models provided similar results. Whichever parent had PD, the age at onset of index cases correlated with their age at the time the affected parent developed PD, but not with the age of onset in the affected parent. Since the degree of environmental exposure shared by parents and children decreases as the child's age increases, these results indicate that PD is usually caused by an accumulation of transient environmental events. We provide evidence that this is not only true for sporadic cases but also for the majority of familial ones.

Accumulation of acid-fast lipochrome bodies in glial cells of the midbrain nigral lesion in Parkinson's disease

To confirm or refute the proposed link between nocardiae and Parkinson's disease (PD), we investigated the presence of acid-fast spherical structures similar to filterable nocardiae at the midbrain nigral lesions of three patients with PD. Many clusters of acid-fast lipochrome bodies were dense around blood vessels in the two patients with Hoehn and Yahr stage II and III PD. These clusters were present in the vicinity of melanin-pigmented neurons in the three PD patients studied. Examination of adjacent hematoxylin-and-eosin-stained sections indicated that they consisted of yellow-green granules, bodies, and aggregates in ballooned glial cells. On the other hand, no clusters of acid-fast lipochrome bodies were observed at the compacta region of three control patients. Our results suggest that the immunological and genetic relationship between the acid-fast lipochrome bodies and filterable nocardiae should be investigated.

Age-standardized incidence and prevalence of Parkinson's disease in a Swedish community

Parkinson's disease (PD) shows a geographical variation. All prescriptions for anti-parkinsonian drugs were recorded for a half-year in a region with low L-dopa consumption. Hospital and outpatient records were studied and physicians were asked to supply details of PD patients in the region, with 147,777 inhabitants. The crude prevalence was 115 PD per 100,000 inhabitants, based on 170 cases. In contrast to other studies we report an age-standardized prevalence, which was 76 per 100,000, using the European Standard Population as reference. The corresponding approximate incidences were 11.0 (crude) and 7.9 (age-standardized) per 100,000 person-years. Male preponderance appeared in all age groups. Mean age at onset was 65.6 years, the highest figure reported. Variation between studies for age at onset, differences in prevalence, and male preponderance suggest environmental risk factors to be of importance for PD.

Parkinson's disease epidemiology in the Northampton District, England, 1992

In a population of 302,000, in a Midlands district of England, the estimated prevalence of idiopathic Parkinson's disease (IPD) increased from 108 to 121 per 100,000 from 1982 to 1992. Individual general practice prevalence ranged quite widely. Webster ratings were significantly more often scored in 1992, but at a lower level of severity, suggesting earlier diagnosis. Incidence in 1992 was estimated as 12 per 100,000 per annum. Micrographia, when copying interlocking pentagons, was significantly related to Hoehn & Yahr scores. Over the 10-year period, there has been a considerable change in prescribing: a positive response to medication was confirmed as a good diagnostic indicator. Progression of symptoms and an increase of physical disability was noted in those of the 1982 study alive in 1992.

Prevalence of Parkinson's disease in the elderly: a population study in Gironde, France

We investigated the prevalence of Parkinson's disease in a representative sample of the elderly population living in the Gironde département, France. Among 3149 people over age 65, the prevalence ratio for Parkinson's disease was 1.4%, without significant difference between men and women. We found that age-specific prevalence ratios increased with age from 0.5% in the age group 65 to 69 to 6.1% in individuals over age 90. This age pattern is consistent with that found in other population-based studies. Interestingly, the slope of age-specific prevalence ratios for Parkinson's disease was similar to that previously reported for Lewy bodies. Our study showed that a high proportion (42%) of Parkinson's disease cases in elderly subjects living in institutions were undiagnosed.

Prevalence of anti-parkinson drugs' use in Ferrara, northern Italy, 1988

INTRODUCTION

The period prevalence rate for anti-parkinson drugs (APD) use was reported in the Local Health Service of Ferrara (USL 31), Northern Italy, in 1988 (resident population: 177,000 inhabitants).

MATERIAL AND METHODS

The study was performed through the analysis of the complete list of APD prescriptions in the USL 31 area provided by the computerized archives of USL 31 and the identification code of the patients which is unique for each resident of USL 31. The patients treated with neuroleptics known to be potential parkinsonism-inducing drugs were excluded.

RESULTS

The period prevalence rate for APD users was 456.9 per 100,000 population. The prevalence rate for dopa derivatives users was 391.3 per 100,000. The prevalence did not varied between rural and urban zones of USL 31 both for APD and dopa derivatives users. A higher prevalence was obtained in a small rural commune of USL 31 both for APD users (758.5 per 100,000) and dopa derivatives users (718.6 per 100,000) than in the other 4 communes in which the study area is subdivided.

CONCLUSION

The reported prevalence could provide information on the occurrence of most parkinsonisms in the study area and some suggestion on the role of possible environmental factors.

A case control study of CSF copper, iron and manganese in Parkinson disease

To elicit possible variations in the CSF concentrations of copper, iron and manganese due to Parkinson disease (PD) or to the stage reached, we tested 11 patients with idiopathic PD, 6 untreated and 5 on long term L-dopa, versus 22 age and sex matched patients with other neurological disorders (control group-CG). The CSF levels of the three metals, measured by electrothermal atomization, did not differ significantly between the PD group and CG or between either of the PD subgroups and CG. Our findings therefore do not support the hypothesis that CSF Cu is a marker of PD.