Black tea helps one type of Parkinson's, but soda and pesticides worsen another

Black tea helps one type of Parkinson's, but soda and pesticides worsen another

Researchers discover subtype-specific effects of tea, soda and pesticides on Parkinson's disease, showing how lifestyle and environment can influence the severity of motor symptoms long after diagnosis.

In a recent article published in the JournalNPJ Parkinson's diseaseResearchers examined how lifestyle factors and environmental exposures influence the severity of motor symptoms in patients with Parkinson's disease over time.

They found that black tea consumption was associated with milder motor symptoms in one form of the disease. At the same time, pesticide exposure and consumption of caffeinated soda have been implicated in worsening motor symptoms in another disease type.

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The role of sugar suggested: Diet caffeinated soda, which lacks the high sugar of regular soda, showed no association with motor severity. This suggests that sugar may be the primary driver of regular soda's negative effects.

Parkinson's disease is a neurodegenerative disease that currently affects approximately 12 million people worldwide. From 1990 to 2021, cases increased by over 60%. The lack of a cure means the burden on society continues to grow.

Approximately 15% of Parkinson's cases are caused by single gene mutations or strong risk factors, with the LRRK2 G2019S variant being the most common for autosomal dominant Parkinson's disease (LRRK2-PD).

Previous research suggests that LRRK2-PD patients often experience more severe motor problems but less severe non-motor symptoms compared to idiopathic Parkinson's disease (IPD) patients.

Environmental and lifestyle factors also play a significant role in the development and progression of this condition. Pesticide exposure is an established risk factor associated with earlier disease and more rapid progression.

Other environmental risks such as air pollution, solvents and heavy metals show mixed results. Drinking coffee and smoking appear consistently protective and delay onset in both IPD and LRRK2-PD, while caffeinated soda may initiate in LRRK2-PD.

However, the impact of these factors on motor severity over time remains unclear, particularly with smoking and caffeine intake. Cross-sectional studies suggest that smoking could worsen symptoms after onset, creating a paradox in which a factor that is protective against disease development could be detrimental after diagnosis.

Therefore, more robust longitudinal studies with large cohorts are needed to clarify how environment and lifestyle impact motor symptom progression, particularly the distinction between LRRK2-PD and IPD.

About the study

Gender-specific susceptibility: Women with IPD who drank caffeinated soda experienced a much greater worsening of motor symptoms than men.

This study used data from two large online cohorts. Participants with Parkinson's disease were recruited and followed through routine online assessments of non-motor and motor symptoms as well as detailed questionnaires on lifestyle habits and environmental exposures.

Ethical approval and informed consent were recorded for both cohorts.

To ensure consistency, only participants with an age greater than 25 years, disease duration less than 50 years, and at least three motor assessments were included. This resulted in 5,134 IPD patients and 81 LRRK2-PD patients.

Motor symptom severity was measured using a cumulative score collected consistently in both cohorts. Follow-up lasted up to 35 months for one cohort and 60 months for the second, divided into discrete periods for analysis.

Environmental and lifestyle factors, including pesticide exposure, smoking, and caffeine intake, were measured using standardized Parkinson's disease risk factor questionnaires.

Linear mixed effects models were used to assess the relationship between these factors and progression of motor symptoms over time. Models were adjusted for baseline, disease duration, experience of off-episodes, and sex, with patient identification number as a random effect.

Significance thresholds were adjusted for multiple comparisons in pesticide exposure analyses. Other analyzes were exploratory. This approach ensured a robust, longitudinal assessment of how environment and lifestyle may influence motor outcomes in PD.

Key Findings

Unique susceptibility of LRRK2-PD: The beneficial effect of black tea was specific to LRRK2-PD, with a significant interaction between PD type and tea consumption (P = 0.045), meaning that black tea not only helped, but helped differentially in this genetic subtype.

In multiple assessments, motor symptoms gradually worsened in both groups, but IPD patients generally showed more severe progression than LRRK2-PD patients.

Notably, exposure to pesticides at work was associated with greater motor severity in IPD patients in the PPMI-Online cohort, with a similar but non-significant trend observed in the Fox Insight cohort. This union persisted after adaptation to sex. No such association was found in LRRK2-PD patients.

Smoking was also associated with increased motor symptom severity over time in IPD patients. This effect was significant in the PPMI online cohort, but only a subtle trend was observed in the Fox Insight cohort. This effect held after controlling for sex.

Regarding caffeinated beverages, black tea consumption did not influence motor severity in IPD but was associated with milder symptoms in LRRK2-PD patients. While the authors caution that this subgroup was small, they strengthened this preliminary finding by replicating it in a second, independent cohort of LRRK2-PD patients.

Conversely, caffeinated soda consumption was associated with more severe motor symptoms in IPD patients and showed a similar trend in LRRK2-PD, although less robust. The paper notes that caffeinated diet soda, which lacks high sugar content, showed no such association.

Interestingly, the association between caffeinated soda intake and worse motor symptoms was stronger in women than in men with IPD. Coffee and green tea consumption showed no clear influence on motor symptom progression in either group.

Conclusions

This study highlights the impact of environmental and lifestyle factors on the progression of Parkinson's disease. Pesticide exposure and caffeinated soda intake were found to be associated with worse motor symptoms in IPD, while smoking showed a weaker association that was not consistent across both study cohorts.

For LRRK2-PD, black tea consumption appeared protective, although this effect was not observed in IPD, suggesting subtype-specific effects. This finding is notable because it was observed in two independent cohorts, although both were small.

The study's strengths include its large sample size, long follow-up period, and use of two independent cohorts, supporting robust results. However, small LRRK2-PD samples limit generalizability, and other monogenic forms have not been thoroughly investigated. Lack of data on drug doses, dietary details (e.g., sugar intake), and potential recall bias are additional limitations.

Still, the study highlights that environmental exposures, which are harder to control than lifestyle choices, can worsen Parkinson's symptoms even after the disease begins. The results also underscore how a factor like smoking can be protective before initiation but potentially harmful afterward, and suggest how ingredients like sugar in soda may play a role of caffeine.

Future research should confirm these results in larger, diverse genetic groups and use objective measures of exposure. Understanding these relationships may help inform prevention and management strategies for different subtypes of Parkinson's disease.

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