Parkinson's disease is not a long-latency illness

Depression and the subsequent risk of Parkinson's disease in the NIH-AARP Diet and Health Study

We conducted a case-control study to examine the association between depression and Parkinson's disease (PD). Participants included 992 PD cases diagnosed after 2,000 and 279,958 individuals without PD from the NIH-AARP Diet and Health Study follow-up survey. Physician-diagnosed depression and PD were self-reported with information on the year of diagnosis in the following categories: before 1985, 1985-1994, 1995-1999, and 2000-present. Only PD cases diagnosed after 2000 were included in the analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were derived from logistic regression models, adjusted for age, gender, educational level, marital status, smoking, and coffee drinking. Individuals with depression diagnosed after 2000 were more likely to report a concurrent diagnosis of PD than those without depression (OR = 4.7, 95% CI = 3.9, 5.7). Depression diagnosed before 2000 was also associated with higher odds of PD diagnosed after 2000 (OR = 2.0, 95% CI = 1.6, 2.4). This association was stronger for depression diagnosed in 1995-1999 (OR = 2.7, 95% CI = 2.0, 3.6), but was also noted for depression diagnosed in 1985-1994 (OR = 1.6, 95% CI = 1.1, 2.3) or even before 1985 (OR = 1.7, 95% CI = 1.3, 2.3). This association was not modified by other factors and persisted in an analysis excluding participants who reported poor health status. The results suggest that depression may either be a very early symptom of PD or share common etiological factors with PD.

Risk of Parkinson's disease after tamoxifen treatment

Background

Women have a reduced risk of developing Parkinson's disease (PD) compared with age-matched men. Neuro-protective effects of estrogen potentially explain this difference. Tamoxifen, commonly used in breast cancer treatment, may interfere with the protective effects of estrogen and increase risk of PD. We compared the rate of PD in Danish breast cancer patients treated with tamoxifen to the rate among those not treated with tamoxifen.

Methods

A cohort of 15,419 breast cancer patients identified from the Danish Breast Cancer Collaborative Group database was linked to the National Registry of Patients to identify PD diagnoses. Overall risk and rate of PD following identification into the study was compared between patients treated with tamoxifen as adjuvant hormonal therapy and patients not receiving tamoxifen. Time-dependent effects of tamoxifen treatment on PD rate were examined to estimate the likely induction period for tamoxifen.

Results

In total, 35 cases of PD were identified among the 15,419 breast cancer patients. No overall effect of tamoxifen on rate of PD was observed (HR = 1.3, 95% CI: 0.64-2.5), but a PD hazard ratio of 5.1 (95% CI: 1.0-25) was seen four to six years following initiation of tamoxifen treatment.

Conclusions

These results provide evidence that the neuro-protective properties of estrogen against PD occurrence may be disrupted by tamoxifen therapy. Tamoxifen treatments may be associated with an increased rate of PD; however these effects act after four years, are of limited duration, and the adverse effect is overwhelmed by the protection against breast recurrence conferred by tamoxifen therapy.

How valid is dopamine transporter imaging as a surrogate marker in research trials in Parkinson's disease?

To use functional imaging data as indices of disease progression, it is essential that methods are valid. It is not possible for that validation to come from pathology and the methods can only gain validity from the relationship to clinical indices of progression. Validity as a measurement of disease progression depends upon sensitivity to clinical progression, low scan-to-scan error, and resilience to confounding effects. Data from the available dopamine transporter (DAT) positron emission tomography (PET) and single photon emission computed tomography (SPECT) studies are examined for these three key factors. Presently, there are insufficient data to enable the satisfactory design of neuroprotection studies and to enable statements on their relevance to disease progression and neuroprotection. The recently completed CALM-PD neuroimaging study is examined. There is sufficient doubt surrounding the sensitivity, reproducibility, and confounding effects in this study that these data should not be used to formulate a decision on de novo therapy in Parkinson's disease.

123I-IPT brain SPECT study in essential tremor and Parkinson's disease

OBJECTIVE

To investigate nigral neuronal damage in patients with isolated postural tremor and those with postural and rest tremor without parkinsonism.

METHODS

Using [123I]-N-(3-iodopropen-2-yl)-2 -carbomethoxy-3beta-(4-chlorophenyl) tropane SPECT, we measured the basal ganglia-occipital cortex/occipital cortex ([BG-OCC]/OCC) uptake ratios in 21 control subjects and patients with isolated postural tremor (n = 9), postural and rest tremor (n = 6), and PD (n = 11).

RESULTS

In the patients with PD, the means (+/-SD) of the (BG-OCC)/OCC ratios of the ipsilateral (2.35+/-0.37) and the contralateral (1.97+/-0.33) sides to the more severely affected limbs were significantly lower than the mean of the bilateral (BG-OCC)/OCC ratios of the age-matched control subjects (3.83+/-0.66). The mean (+/-SD) of the bilateral (BG-OCC)/OCC ratios of the patients with isolated postural tremor (3.60+/-0.83) was comparable with that of the age-matched control subjects. However, the mean (+/-SD) of the bilateral (BG-OCC)/OCC ratios of the patients with postural and rest tremor (2.61+/-0.18) was lower than that of the control subjects (p < 0.05). The mean of the bilateral (BG-OCC)/OCC ratios of the patients with postural and rest tremor was comparable with that of the side ipsilateral to the severely affected limbs of the patients with PD. However, it was higher than that of the side contralateral to the limbs more severely affected by PD. Four of the six patients with postural and rest tremor had (BG-OCC)/OCC ratios lower than 2 standard deviations from the mean of the age-matched control subjects.

CONCLUSIONS

Later in their clinical courses, some patients with postural tremor may acquire rest tremor in association with mild substantia nigra neuronal loss.

Neuroprotective therapies

Though effective symptomatic therapies for Parkinson's disease exist, currently no treatment is proven to slow the progression of the underlying disease. Our growing understanding of the mechanisms of neuronal models, however, offers hope that neuroprotective strategies will soon be a standard part of the treatment of PD. Current approaches to the development of neuroprotective strategies are based on the hypothesized roles of oxidative stress and excitotoxicity in the degenerative process. In this article, we review evidence in support of these hypotheses as well as attempts to achieve neuroprotection in PD based on these and other mechanisms.