Hypertension May Increase Risk of Parkinson’s, Study Reports

hypertension, Parkinson's risk

Patients with hypertension may be at a higher risk for Parkinson’s disease, according to a review of population-based studies.

The review, “Association between Hypertension and the Risk of Parkinson’s Disease: A Meta-Analysis of Analytical Studies,” appeared in the journal Neuroepidemiology.

Hypertension may cause damage in blood vessels in specific brain areas, such as the basal ganglia, which contain the substantia nigra and the striatum. In Parkinson’s, the substantia nigra experiences progressive loss of dopamine-producing neurons while the striatum has low levels of this neurotransmitter. This suggests a link between hypertension and greater prevalence of Parkinson’s.

However, previous studies have had contradictory findings, with some reporting a greater risk and others suggesting a lower risk for Parkinson’s.

To clarify this link, scientists from Qingdao University in China conducted a meta-analysis — a statistical study that combines the results of various studies — and a systematic review of the available literature.

Seven online databases were searched for literature up to July 13, 2018. From these databases, 27 observational studies were included, nine of which were population-based cohort studies (with a total of 1,230,085 participants) and 18 were case-control studies (32,121 participants). All but one study were from either North America, Europe, or Asia.

Five studies assessed hypertension by medical record, 11 through questionnaire, and two by measuring blood pressure.

In the cohort studies — prospective analyses where groups are followed to compare the risk of a specific outcome — patients with hypertension were at a significantly greater risk for Parkinson’s than participants with normal blood pressure. This was confirmed after excluding the two studies that were leading to high variability of results.

“Based on population-based cohort studies, this meta-analysis indicated hypertension might increase the risk of [Parkinson’s],” the researchers wrote.

In contrast, case-control studies — retrospective analyses where participants with or without hypertension are known from the start — suggested that hypertension might lower the risk for Parkinson’s. However, a subgroup analysis based on non-hospital records revealed no association. The variability observed in these studies was mainly due to different results in controls, depending on whether they were from hospital settings or not.

According to the team, the contradictory results in the two types of studies may have been due to a higher proportion of elderly controls with hypertension in case-control studies, particularly those conducted in the hospital setting.

Due to the link between aging and both hypertension and Parkinson’s, these studies are not suitable for exploring the risk of Parkinson’s in hypertension, the researchers said.

Among the study’s limitations, they mentioned not accounting for the use of anti-hypertensive medications as well as not being able to calculate an overall risk for Parkinson’s combining the two types of studies.

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Exercise Can Raise BDNF Levels, Alleviate Depression in Parkinson’s Patients, Review Shows

BDNF levels

Levels of brain-derived neurotrophic factor (BDNF) — a protein important in promoting the survival of dopaminergic neurons — are abnormally low in patients with Parkinson’s disease, regardless of whether these patients also have depression, a common non-motor symptom associated with the disease, a systematic review study reveals.

The study also revealed that exercise can increase BDNF levels in Parkinson’s patients, highlighting exercise’s potential not only to treat depression, but also motor symptoms typically associated with Parkinson’s disease.

The systematic review, “Plasma levels of brain-derived neurotrophic factor in patients with Parkinson disease: A systematic review and meta-analysis,” was published in Brain Research.

BDNF is an abundant protein whose main function is to protect dopaminergic neurons located in the substantia nigra — a region of the brain responsible for movement control — that are gradually lost in the course of Parkinson’s disease.

Although no literature consensus exists, some studies have shown that blood serum BDNF levels decrease in patients with depression and increase after intense exercise in healthy adults.

In this systematic review, the authors focused on gathering and discussing data from previous studies assessing blood serum levels of BDNF in Parkinson’s patients.

After a thorough screening in three different databases (MEDLINE, EMBASE and SCOPUS), 12 eligible studies were selected, including five comparing serum BDNF levels of Parkinson’s patients to those of healthy control subjects and three comparing serum BDNF levels of depressed and non-depressed Parkinson’s patients.

Data revealed that Parkinson’s patients tend to have lower levels of BDNF in their serum, compared to healthy control individuals (mean difference of 2.99 ng/mL). Parkinson’s patients who also had depression had even lower levels of BDNF compared to healthy control subjects (mean difference of 4.83 ng/mL).

No differences in BDNF levels were found between depressed and non-depressed Parkinson’s patients.

There was also a positive correlation between serum BDNF levels and patients’ male gender, disease duration and Hoehn and Yahr motor score — a commonly used system to describe the progression of Parkinson’s symptoms.

There is “a direct relationship between [Parkinson’s disease] progression and worsening of motor symptoms and higher serum BDNF. We believe that this could be a result of a compensatory mechanism in response to progressive loss of dopaminergic neurons of the substantia nigra and progressive [reduction] of neurotrophin expression in the remaining neurons. This could also reflect a possible effect of medications, namely antidepressants and dopamine replacement therapy,” researchers said.

Four studies also analyzed the effects of exercise on serum BDNF levels, while two others focused on the relationship between Parkinson’s disease severity and patients’ physical capacity and serum BDNF levels.

While there was no relationship between patients’ physical capacity and serum BDNF levels, a significant increase in BDNF levels was seen in patients with mild to moderate Parkinson’s after four or eight weeks of physical training, which was accompanied by an improvement of UPDRS motor scores and patients’ performance on the 6-minute walking test, used to assess aerobic capacity and endurance.

Another study reported similar findings in depressed Parkinson’s patients who participated in a 12-week exercise program.

“Our results proved that PD is of equal potential to [decrease] BDNF expression as depression, which is a common co-morbid condition in PD. The potential for exercise to induce BDNF expression in PD patients justifies that physical training might prove useful to treat depressive symptoms as well as motor complications of PD patients,” researchers concluded.

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Lack of Exercise Increases Parkinson’s Risk in Men, Review Study Confirms

Men who lack physical activity have a higher risk of developing Parkinson’s disease at some point in their lives, a systematic review has found. Importantly, findings revealed that even moderate exercise can be enough to counteract this effect.
The review, “Association of Levels of Physical Activity With Risk of Parkinson Disease,” was published in JAMA Network Open.
Parkinson’s disease, the second most prevalent neurodegenerative disease of the elderly (after Alzheimer’s disease), is characterized by the gradual loss of muscle control, sometimes accompanied by cognitive deficits.
The underlying causes of Parkinson’s disease are still poorly understood by scientists, but likely involve a combination of genetic and environmental risk factors. In the past 20 years, several prospective studies have focused on the effect of lifestyle factors, such as exercise, on Parkinson’s.
Although physical activity is known to decrease the risk of developing several conditions, including cardiovascular disease, stroke and diabetes, systematic studies addressing the impact of physical activity on Parkinson’s risk are few in number and often inconsistent regarding their methodology and data interpretation.
This systematic review focused on gathering data from previously published prospective studies to quantify the dose-response association between physical activity and Parkinson’s risk.
Following an initial period of literature research performed by two independent investigators, a total of eight prospective studies involving 544,336 participants — including 2,192 Parkinson’s patients with a median follow-up period of 12 years — focused on the relationship between physical activity and Parkinson’s risk, were included in the review.
Pooled data from all the studies showed that participants included in the highest category of total physical activity had a 29% lower risk of developing Parkinson’s compared to those who did not engage in any moderate-to-vigorous physical activity. Conversely, light physical activity was not linked to Parkinson’s risk.
Further subgroup analyses revealed that the relationship between physical activity and Parkinson’s risk was not influenced by geographic region, follow-up duration, population size, or study quality. They were  affected, however, by gender, as the link between exercise and Parkinson’s risk was more robust among men, regardless of physical activity levels, compared to women.
Finally, the dose-response analysis showed that for each increase of 10 metabolic equivalents of task (MET) — a method to measure the energy cost of physical activities — of hours per week in total or moderate-to-vigorous physical activity, Parkinson’srisk in men decreased by 10% and 17%, respectively. This dose-response effect was not observed among women.
“[O]ur pooled analysis of more than half a million adults revealed that higher levels of physical activity —particularly moderate to vigorous activity — are associated with a lower risk of developing PD [Parkinson’s disease]. These benefits were significant among men, but were less robust among women,” researchers wrote.
“These findings may help guide physicians and health care policy makers in making recommendations and developing guidelines with respect to the degree of physical activity that can help reduce the risk of PD at both the individual level and the population level. More epidemiological studies with large sample size and detailed quantification of physical activity will help establish more precise information regarding this association,” they concluded.
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Source: Parkinson's News Today