Exploring the relationship between caffeine intake and essential tremor

Association of Diet With Essential Tremor: A Narrative Review

Essential tremor is a neurological disorder categorized by the rhythmic shaking of the upper limbs, lower limbs, neck, or head. The etiology of essential tremor is believed to be genetic variations, environmental factors, lifestyle, etc. Poor lifestyle and diet are important factors contributing to the onset of various disorders. Environment and lifestyle play a significant part in the dietary habits of an individual. Some diet components may probably be associated with the etiopathogenesis or progression of the essential tremor. Dietary habits may be a key influence on the commencement of tremors in healthy individuals. Typically, the diet of essential tremor patients is not supervised. It may also intensify the tremors in essential tremor patients. Association of the diet with the essential tremor can shed light on the root of tremor aggravating aspect and aid in diet modification in essential tremor patients. The aim of the review is to establish a relation between the diet with etiopathogenesis and the progression of essential tremor. The review includes studies providing information about essential tremor and correlating essential tremor with diet, lifestyle, environment, and genetic factors. Studies that did not provide a link to the association of essential tremor were excluded. The interpretation of the research indicated that genetic variations might be triggered due to enzymatic changes triggered by dietary patterns. Dietary components showed ambiguous, weak, strong, or no association. Essential tremor may be influenced by diet. Further research must be carried out on essential tremor patients in the nutritional domain. Physicians may monitor the diet of the essential tremor patients and record the progress of the disorder on its basis to manage the patients with essential tremor and provide better services.

The Pathophysiology and Treatment of Essential Tremor: The Role of Adenosine and Dopamine Receptors in Animal Models

Essential tremor (ET) is one of the most common neurological disorders that often affects people in the prime of their lives, leading to a significant reduction in their quality of life, gradually making them unable to independently perform the simplest activities. Here we show that current ET pharmacotherapy often does not sufficiently alleviate disease symptoms and is completely ineffective in more than 30% of patients. At present, deep brain stimulation of the motor thalamus is the most effective ET treatment. However, like any brain surgery, it can cause many undesirable side effects; thus, it is only performed in patients with an advanced disease who are not responsive to drugs. Therefore, it seems extremely important to look for new strategies for treating ET. The purpose of this review is to summarize the current knowledge on the pathomechanism of ET based on studies in animal models of the disease, as well as to present and discuss the results of research available to date on various substances affecting dopamine (mainly D3) or adenosine A1 receptors, which, due to their ability to modulate harmaline-induced tremor, may provide the basis for the development of new potential therapies for ET in the future.

Essential tremor

Essential tremor (ET) is one of the most common movement disorders, with a reported >60 million affected individuals worldwide. The definition and underlying pathophysiology of ET are contentious. Patients present primarily with motor features such as postural and action tremors, but may also have other non-motor features, including cognitive impairment and neuropsychiatric symptoms. Genetics account for most of the ET risk but environmental factors may also be involved. However, the variable penetrance and challenges in validating data make gene-environment analysis difficult. Structural changes in cerebellar Purkinje cells and neighbouring neuronal populations have been observed in post-mortem studies, and other studies have found GABAergic dysfunction and dysregulation of the cerebellar-thalamic-cortical circuitry. Commonly prescribed medications include propranolol and primidone. Deep brain stimulation and ultrasound thalamotomy are surgical options in patients with medically intractable ET. Further research in post-mortem studies, and animal and cell-based models may help identify new pathophysiological clues and therapeutic targets and, together with advances in omics and machine learning, may facilitate the development of precision medicine for patients with ET.

Etiologic links between environmental and lifestyle factors and Essential tremor

Essential tremor (ET) is one of the most common adult movement disorders, characterized by clinical tremor and other nonmotor symptoms. It is a progressive disease that shares features with other neurodegenerative diseases. ET is a complex disease with both genetic and environmental underpinnings. While genetic forms of ET are well recognized, the role of environmental and lifestyle factors in ET has been debated. Studies suggest that exposure to neurotoxic compounds such as β-carboline alkaloids and ethanol are potential risk factors for ET, while antioxidant intake may be protective. In addition, smoking acts as a protective factor in ET, parallel to its effects in other neurological diseases. New evidence points to pesticide and lead exposure as potential risk factors. There is growing evidence to suggest that environmental and lifestyle factors play a role in ET but additional research is needed in order to completely understand their cause and effect association. There is also a need for larger case-control and prospective cohort studies across different populations to further evaluate the etiological importance of these factors in ET.

Elevated brain harmane (1-methyl-9H-pyrido[3,4-b]indole) in essential tremor cases vs. controls

BACKGROUND

Harmane (1-methyl-9H-pyrido[3,4-β]indole), a potent neurotoxin that has tremor-producing properties in animal models, is present in many foods; although we have demonstrated a difference in tissue harmane concentrations in ET cases vs. controls, all work to date has involved blood samples.

OBJECTIVES

We quantified harmane concentrations in human cerebellum, a brain region of particular pathogenic interest in essential tremor (ET), comparing ET to control brains.

METHODS

Cerebellar cortex was snap frozen and stored at -80°C in aliquots for biochemical analyses. Harmane concentration was assessed using high performance liquid chromatography.

RESULTS

Geometric mean brain harmane concentrations (adjusted for postmortem interval [PMI] and freezer time) were higher in ET cases than controls: 1.0824 (95% confidence interval=0.9405-1.2457) vs. 0.8037 (0.6967-0.9272), p=0.004. Geometric mean of brain harmane concentrations (adjusting for PMI and freezer time) was highest in ET cases who reported other relatives with tremor (1.2005 [0.8712-1.6541]), intermediate in ET cases without family history (1.0312 ([0.8879-1.1976]), and both were significantly higher than controls (p=0.02).

CONCLUSIONS

This study provides additional evidence of a possible etiological importance of this toxin in some cases of the human disease ET.

Wine drinking and essential tremor: a possible protective role

The purpose of this study was to evaluate the possible association of cigarette smoking, coffee drinking, and wine consumption with essential tremor using a matched case-control design. Cases and controls were enrolled from 6 Movement Disorder centers in central-southern Italy. Essential tremor was diagnosed according to Bain's criteria. Three unrelated healthy controls (not affected by neurological disorders) per each enrolled case, matched by sex and age (± 5 years), were selected. A standardized questionnaire was administered to record demographic, epidemiological, and clinical data. All cases and controls underwent a standard neurological examination. Adjusted odds ratios and 95% confidence intervals were estimated using conditional logistic regression for the matched cases and controls. Eighty-three patients with essential tremor (38 men and 45 women; mean age, 68.2 ± 8.6 years) and 245 matched control subjects (113 men and 132 women; mean age, 68.4 ± 9.7 years) were enrolled in the study. Multivariate analysis showed a significant negative association between essential tremor and wine consumption preceding the onset of disease (adjusted odds ratio, 0.23; 95% confidence interval, 0.08-0.64; P = .0005) with a significant dose effect (1-2 glass of wine per day: odds ratio, 0.32; 95% confidence interval, 0.10-0.95; P = .04; more than 3 glass of wine per day: odds ratio, 0.14; 95% confidence interval, 0.03-0.62; P = .01). In our sample no association between essential tremor and cigarette smoking or coffee drinking was found. Our data suggest a negative association between wine drinking and essential tremor, which could be explained by the long-term neuroprotective effect of its antioxidant components.

Environmental epidemiology of essential tremor

BACKGROUND

Essential tremor (ET) is one of the most common neurological disorders. Despite this, the disease mechanisms and etiology are not well understood. While susceptibility genotypes undoubtedly underlie many ET cases, no ET genes have been identified thus far. As with many other progressive, degenerative neurological disorders, it is likely that environmental factors contribute to the etiology of ET. Environmental epidemiology is the study in specific populations or communities of the effect on human health of physical, biologic and chemical factors in the external environment. The purpose of this article is to review current knowledge with regards to the environmental epidemiology of ET.

RESULTS

As will be discussed, a series of preliminary case-control studies in recent years has begun to explore several candidate toxins/exposures, including harmane (1-methyl-9H-pyrido[3,4-b]indole), lead and agricultural exposures/pesticides.

CONCLUSIONS

While several initial results are promising, as will be discussed, additional studies are needed to more definitively establish whether these exposures are associated with ET and if they are of etiological importance.

Population-based prospective study of cigarette smoking and risk of incident essential tremor

BACKGROUND

Smoking cigarettes is associated with lower risk of Parkinson disease (PD). Despite the clinical links between PD and essential tremor (ET), there are few data on smoking in ET. One study showed an association between smoking and lower ET prevalence. We now study whether baseline smoking is associated with lower risk of incident ET.

METHODS

Using a population-based, cohort design, baseline cigarette smoking habits were assessed in 3,348 participants in an epidemiologic study in Spain, among whom 77 developed incident ET.

RESULTS

There were 3,348 participants, among whom 397 (11.9%) were smokers at baseline. Five (6.5%) of 77 incident ET cases had been smokers at baseline, compared with 392 (12.0%) of 3,271 controls (p = 0.14). Baseline pack-years were lower in incident ET cases than in controls (9.2 +/- 17.7 vs 15.7 +/- 28.4, p = 0.002). Participants were stratified into baseline pack-year tertiles, and few incident ET cases were in the highest tertile (4 [5.2%] cases vs 431 [13.2%] controls, p = 0.039). In Cox proportional hazards models, the highest baseline pack-year tertile was associated with lower risk of incident ET; those in the highest pack-year tertile were one-third as likely to develop ET when compared with nonsmokers (relative risk [RR] 0.37, 95% CI 0.14-1.03, p = 0.057 [unadjusted model] and RR 0.29, 95% CI 0.09-0.90, p = 0.03 [adjusted model]).

CONCLUSIONS

We demonstrated an association between baseline heavy cigarette smoking and lower risk of incident essential tremor. The biologic basis for this association requires future investigation.

Dietary epidemiology of essential tremor: meat consumption and meat cooking practices

BACKGROUND/AIM

Harmane [1-methyl-9H-pyrido(3,4-b)indole] is a tremor-producing neurotoxin. Blood harmane concentrations are elevated in essential tremor (ET) patients for unclear reasons. Potential mechanisms include increased dietary harmane intake (especially through well-cooked meat) or genetic-metabolic factors. We tested the hypothesis that meat consumption and level of meat doneness are higher in ET cases than in controls.

METHODS

Detailed data were collected using the Lawrence Livermore National Laboratory Meat Questionnaire.

RESULTS

Total current meat consumption was greater in men with than without ET (135.3 +/- 71.1 vs. 110.6 +/- 80.4 g/day, p = 0.03) but not in women with versus without ET (80.6 +/- 50.0 vs. 79.3 +/- 51.0 g/day, p = 0.76). In an adjusted logistic regression analysis in males, higher total current meat consumption was associated with ET (OR = 1.006, p = 0.04, i.e., with 10 additional g/day of meat, odds of ET increased by 6%). Male cases had higher odds of being in the highest than lowest quartile of total current meat consumption (adjusted OR = 21.36, p = 0.001). Meat doneness level was similar in cases and controls.

CONCLUSION

This study provides evidence of a dietary difference between male ET cases and male controls. The etiological ramifications of these results warrant additional investigation.