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Journal of Alzheimer’s Disease 20 (2010) S205–S220 S205
DOI 10.3233/JAD-2010-091459
IOS Press
Review Article
Effects of Caffeine in Parkinson’s Disease:
From Neuroprotection to the Management of
Motor and Non-Motor Symptoms
Rui D.S. Prediger∗
Departamento de Farmacologia, Centro de Ci ˆencias Biol´ogicas, and Centro de Neuroci ˆencias Aplicadas (CeNAp),
Hospital Universit ´ario; Universidade Federal de Santa Catarina, UFSC, Florian ´opolis-SC, Brazil
Accepted 23 December 2009
Abstract. Parkinson’s disease (PD) is the second most common neurodegenerative disorder affecting approximately 1% of
the population older than 60 years. Classically, PD is considered to be a motor system disease and its diagnosis is based
on the presence of a set of cardinal motor signs (rigidity, bradykinesia, rest tremor) that are consequence of a pronounced
death of dopaminergic neurons in the substantia nigra pars compacta. Nowadays there is considerable evidence showing that
non-dopaminergic degeneration also occurs in other brain areas which seems to be responsible for the deficits in olfactory,
emotional and memory functions that precede the classical motor symptoms in PD. The present review attempts to examine results
reported in epidemiological, clinical and animal studies to provide a comprehensive picture of the antiparkinsonian potential
of caffeine. Convergent epidemiological and pre-clinical data suggest that caffeine may confer neuroprotection against the
underlying dopaminergic neuron degeneration, and influence the onset and progression of PD. The available data also suggest
that caffeine can improve the motor deficits of PD and that adenosine A2A receptor antagonists such as istradefylline reduces
OFF time and dyskinesia associated with standard ‘dopamine replacement’ treatments. Finally, recent experimental findings
have indicated the potential of caffeine in the management of non-motor symptoms of PD, which do not improve with the
current dopaminergic drugs. Altogether, the studies reviewed provide strong evidence that caffeine may represent a promising
therapeutic tool in PD, thus being the first compound to restore both motor and non-motor early symptoms of PD together with
its neuroprotective potential.
Keywords: Adenosine receptors, animal models, caffeine, learning and memory, motor deficits, neuroprotection, olfactory system,
Parkinson’s disease
INTRODUCTION
At the beginning of the nineteenth century, when
James Parkinson first described the disorder that bears
his name [1], life expectation was no longer than 45
years. Nowadays, life expectancy is near 80 years, and
∗Correspondence to: Rui D.S. Prediger, PhD, Departamento de
Farmacologia, Universidade Federal de Santa Catarina, Campus
Trindade, 88049-900, Florian´opolis, SC, Brazil. Tel.: +55 48 3721
9491; Fax: +55 48 3337 5479; E-mail: ruidsp@hotmail.com.
the prevalence of Parkinson’s disease (PD) is generally
estimated at 0.3% of the entire population and about
1% in people over 60 years of age [2]. Since the incidence
of the disease increases with age (the most important
risk factor), it is likely that the number of people
suffering from PD will rise steadily in the future.
Classically, PD is considered to be a motor system
disease and its diagnosis is based on the presence of
a set of cardinal motor signs (e.g., rigidity, bradykinesia,
rest tremor and postural reflex disturbance). These
symptoms of PD mainly result from the progressive de-
ISSN 1387-2877/10/$27.50 2010 – IOS Press and the authors. All rights reserved
S206 R.D.S. Prediger / Effects of Caffeine in Parkinson’s Disease
generation of dopamine neurons of the substantia nigra
pars compacta (SNc),which causes a consequent reduction
of dopamine levels in the striatum [3]. Dopaminereplacement
therapy has dominated the treatment of PD
since the early 1960s and although the currently approved
antiparkinsonian agents offer effective relief of
the motor deficits, especially in the early stages of the
disease, they have not been found to alleviate the underlying
dopaminergic neuron degeneration, and drug
efficacy is gradually lost [4]. Moreover, another major
limitation of chronic dopaminergic therapy is the
numerous adverse effects such as the development of
abnormal involuntarymovements (namely dyskinesia),
psychosis and behavioral disturbance (e.g., compulsive
gambling, hypersexuality) [5].
Dopamine replacement therapy is based on the importance
of nigral dopaminergic cell loss and the ensuing
striatal dopamine depletion for the onset of motor
symptoms. However, the neurodegenerative processes
that lead to sporadic PD begin many years before the
appearance of the characteristic motor symptoms, and
additional neuronal fields and neurotransmitter systems
are also involved in PD, including the anterior olfactory
structures, dorsal motor nucleus of vagus, caudal raphe
nuclei, locus coeruleus, the autonomic nervous system,
hippocampus, and the cerebral cortex [6] (Fig. 1).
Accordingly, cholinergic, adrenergic, and serotoninergic
neurons are also lost, which seems to be responsible
for the non-motor symptoms of PD encompassing
olfactory and memory impairments, sleep abnormalities,
and depression, as well as gastrointestinal disturbance,
which precede the classical motor symptoms [7].
Non-motor features of PD invariably do not respond to
dopaminergic medication and are probably the major
current challenge faced in the clinical management of
PD [7].
Therefore, the limitations of the current pharmacological
treatments of PD have led to extensive investigation
of novel non-dopaminergic drugs that may provide
alternative or adjunctive treatment for the relief of
both motor and non-motor symptoms with a reduced
profile of side-effects, as well as to the discovery of
compounds to modify the course of PD. Over the last
decade, several lines of evidence have suggested the potential
of caffeine in the treatment of PD and an increasing
number of studies have tested the potentially beneficial
effects of caffeine (and more selective adenosine
A2A receptor antagonists) in different animal models
and PD patients (Fig. 2).
Convergent epidemiological and pre-clinical data
suggest that caffeine may confer neuroprotection
Fig. 1. Schematic illustration of the potential spread of dysfunction
in different brain regions in Parkinson’s disease during the first three
stages, using the Braak’s staging system [6], until the substantia nigra
pars compacta is affected.
against the underlying dopaminergic neuron degeneration
and can influence the onset and progression of
PD. Indeed, the available data also suggest that caffeine,
through the blockade of adenosine A2A receptors
in striatopallidal neurons, can improve the motor
deficits of PD and that A2A receptor antagonists such
as istradefylline reduce OFF time and dyskinesia associated
to standard ‘dopamine replacement’ treatments.
Finally, recent experimental findings have indicated the
potential of caffeine in the management of non-motor
symptoms (e.g., depression, olfactory and memory dysfunction)
of PD, which do not improve with the current
dopaminergic drugs. The present review attempts
to examine results reported in epidemiological, clinical
and animal studies to provide a comprehensive picture
of the antiparkinsonian potential of caffeine.
CAFFEINE AS A NEUROPROTECTIVE
STRATEGY IN PARKINSON’S DISEASE
Current research on PD is largely devoted to investigating
the etiology of the disease with the aim of
identifying preventive rather than merely symptomatic
treatments. Convergent epidemiologic and experimental
evidence have suggested caffeine and selective
adenosine A2A receptor antagonists as novel potential
strategies to attenuate dopaminergic neurodegeneration
in PD. In a 30-year follow-up study of 8,004 Japanese-
American men in the Honolulu Heart Program, Ross
and colleagues [8] reported an inverse relationship between
consumption of the non-selective adenosine antagonist
caffeine and the risk of developingPD 20 years
later. The age- and smoking-adjusted risk of PD was
five times higher among men who reported no coffee
R.D.S. Prediger / Effects of Caffeine in Parkinson’s Disease S207
A
B
C
Fig. 2. Number of publications containing the keywords “Parkinson’s disease” (PD), “caffeine”, “PD plus caffeine” and “PD plus adenosine
antagonists” found in the main databases analyzed. Panel A illustrates the total number of publications (time spam “all years”) obtained for
the queries comparing ISI Web of KnowledgeSM and SCOPUS. A time-line concerning the publications from year 2000 until October 23rd
of the year 2009 obtained from ISI Web of KnowledgeSMand SCOPUS databases are shown in panels B and C, respectively. In the ISI Web
of KnowledgeSM, data were generated using the keyword “Parkinson disease” rather than “Parkinson’s disease”, which caused a syntax error
because of the apostrophe in this database; This did not occur with SCOPUS.
S208 R.D.S. Prediger / Effects of Caffeine in Parkinson’s Disease
consumption compared with men who reported a daily
consumption of 28 oz or more of coffee [8]. This
finding was subsequently reinforced by further large
prospective studies, which observed a similar inverse
relationship between the consumption of caffeinated
(but not decaffeinated) coffee and the risk of developing
PD. These included the Health Professionals’
Follow-Up Study and the Nurses’ Health Study, involving
47,351 men and 88,565 women [9], and the
Finnish Mobile Clinic Health Examination Survey, involving
19,518 men and women [10]. Men with consumption
of tea and other caffeinated beverages had
reduced risk of PD compared with men who were not
regular caffeine drinkers (< 1 cup/day), whereas no
association was found with the consumption of decaffeinated
coffee [8]. Interestingly, a 50% reduction of
the risk of developing PD was observed among men
with consumption of as low as one cup of caffeine per
day when compared with men consuming n
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