Levodopa in Parkinson disease: a long-term appraisal of mortality

Mortality in levodopa-treated Parkinson's disease

Parkinson's disease (PD) is associated with increased mortality despite many advances in treatment. Following the introduction of levodopa in the late 1960's, many studies reported improved or normalized mortality rates in PD. Despite the remarkable symptomatic benefits provided by levodopa, multiple recent studies have demonstrated that PD patients continue to die at a rate in excess of their peers. We undertook this retrospective study of 211 deceased PD patients to determine the factors associated with mortality in levodopa-treated PD. Our findings confirm that PD is associated with increased mortality in both men and women. Unlike the majority of other mortality studies, we found that women have a greater reduction in lifespan compared to men. We also found that patients with early onset PD (onset at the age of 50 or before) have reduced survival relative to PD patients with later ages of onset. A final important finding is that survival is equal in PD patients treated with levodopa early (within 2 years or less of PD onset) versus later.

Disease modification in Parkinson’s disease: are we there yet with currently available therapies?

SUMMARY Management of Parkinson’s disease (PD) is currently based primarily on dopamine-replacement therapy for the alleviation of motor symptoms. Current medical and surgical therapies can provide long-lasting symptomatic benefit, but they do not modify progression of the disease. Research is ongoing to find a therapy that can provide neuroprotection, defined herein as preventing vulnerable neurons from dying. Studies of neuroprotection are limited by a lack of adequate biomarkers of PD progression and by the confounding symptomatic effects of many putative neuroprotective therapies. Studies have shown that levodopa prolongs life, but they have not clearly shown that it modifies disease progression. Trials of dopamine agonists have demonstrated symptomatic effect but no unequivocal neuroprotective benefits. While some studies of monamine oxidase B inhibitors have been promising, they have not conclusively proven disease modification. Exercise provides many benefits to patients with PD, may modify the progression of the disease and should be part of each patient’s treatment plan.

Seniors with Parkinson's disease: initial medical treatment

Parkinson's disease most often presents after age 60, and patients in this age group are best managed with levodopa therapy as the primary treatment modality. Unlike young-onset parkinsonism (onset <age 40), this older age group is much less prone to subsequent development of levodopa responsive instability (dyskinesias, fluctuations). When these problems do occur in seniors, they usually can be managed by medication adjustments. The treatment goal is to keep patients active and engaged; levodopa dosage should be guided by the patients' responses and not arbitrarily limited to low doses, which may compromise patients' lives.

Estimated life expectancy of Parkinson's patients compared with the UK population

OBJECTIVE

To calculate the best possible estimates for age specific life expectancy (LE) and anticipated age at the time of death (AAD) in patients with Parkinson's disease (PD) compared with the general population in the UK. These may be of greater value to patients than standardised mortality ratios (SMRs), which are usually reported in studies on mortality in PD.

METHODS

A literature review identified articles with data on age stratified life expectancy or SMRs to calculate estimations of LE using the Gompertz function and data on mortality and LE in the UK from the Office of National Statistics and Actuarial Department for the year 2003.

RESULTS

Two UK studies and four from Western Europe were used to estimate LE and AAD for patients with PD from SMRs. The mean LEs of patients with PD compared with the general population were: 38 (SD 5) years for onset between 25 and 39 years compared with 49 (SD 5) years; 21 (SD 5) years for onset between 40 and 64 years compared with 31 (SD 7) years; and 5 (SD 4) years for onset age > or = 65 years compared with 9 (SD 5) years. The average AAD of patients with PD with onset between 25 and 39 years was 71 (SD 3) years and considerably lower than that of the general population (82 (SD 2) years). The difference between average AAD for older individuals with PD (onset > or = 65 years) and the general population was smaller, with an AAD of approximately 88 (SD 7) years compared with 91 (SD 5) years.

CONCLUSIONS

The calculations showed that LE and AAD in PD are reduced for all onset ages but this reduction is greatest in individuals with a young onset. While the results are average estimates, these can provide useful indications of LE and AAD.

Prognosis of Parkinson's disease: Time to stage III, IV, V, and to motor fluctuations

We report a long-term outcome on a large cohort of Japanese patients with Parkinson's disease (PD). A total of 1,768 (793 men, 975 women) consecutive patients visited our clinic from 1 January 1989 to 31 December 2002. Among them, 1,183 patients (531 men, 652 women) came to our clinic within 5 years from the onset of disease and at the Hoehn & Yahr Stage III or less at the first visit. Long-term outcome was evaluated in this subcohort of the patients. We examined the duration to reach Stage III, IV, and V, and the duration to develop wearing off and dyskinesia. Time to reach Stage III was slightly but significantly shorter in women, in that 23.8% of men and 35.3% of women reached Stage III by the end of the 5th year; 49.7% of men and 63.3% of women reached Stage III by the end of the 10th year, and 88.9% of men and 79.9% of women by the end of the 15th year (P < 0.001). Also, durations to develop wearing off and dyskinesia were shorter in women compared to men. These data suggest that the disease progression may be slightly faster for women. Young-onset patients showed significantly longer duration to reach Stage III, IV, and V but shorter duration to develop wearing off and dyskinesia. Not many studies are available in the literature on the long-term outcome of PD, and our data would be useful as a reference.

Challenging conventional wisdom: the etiologic role of dopamine oxidative stress in Parkinson's disease

Oxidative stress is well documented in Parkinson's disease (PD) and has been attributed to dopamine oxidative metabolism. However, evidence of oxidative stress is found in a variety of neurodegenerative disorders, suggesting that more general factors are responsible or that cytodestructive processes secondarily generate oxyradical products. Increasing evidence points away from dopamine metabolism as an important contributor to PD neurodegeneration. Predictions from the dopamine oxidative stress hypothesis of PD reveal multiple inconsistencies. Although the clinical and therapeutic importance of the nigrostriatal dopaminergic system is undeniable, PD neuropathology is much more widespread.

Parkinson's disease: medical and surgical treatment

It has been over three decades since the introduction of L-dihydroxyphenylalanine or levodopa therapy for Parkinson's disease (PD). The early levodopa trials were driven by recognition of a profound cerebral dopamine deficiency state in this disorder. Whereas dopamine fails to cross the blood brain barrier and hence is ineffective as therapy, the amino acid precursor, dopa, is transported across this barrier and provides a substrate for dopamine synthesis. Levodopa is converted to dopamine within the brain by dopa decarboxylase, replenishing central dopamine stores and potentially reversing the motor symptoms of PD.

Levodopa in Parkinson's disease: neurotoxicity issue laid to rest?

Orally administered levodopa remains the most effective symptomatic treatment for Parkinson's disease. The introduction of levodopa therapy is often delayed, however, because of the fear that it might be toxic for the remaining dopaminergic neurons, and thus accelerate the deterioration of the patient's condition. Evidence for levodopa toxicity comes mainly from in vitro studies which have demonstrated that levodopa can damage dopaminergic neurons by a mechanism that probably involves oxidative stress. It is widely accepted, however, that levodopa is not toxic for healthy animals and humans who do not have Parkinson's disease. It has been argued that the lesioned mesostriatal dopaminergic system could be more vulnerable to levodopa-induced toxicity, because the brain extracellular concentrations attained by levodopa are higher when the dopaminergic system is damaged, and remaining dopaminergic neurons experience a process of compensatory hyperactivity. Evidence for in vivo levodopa toxicity in animal models of Parkinson's disease is scarce and contradictory. A comprehensive recent study failed to find any evidence of levodopa toxicity in rats with either moderate or severe lesions of the mesostriatal dopaminergic system. Concerning the hypothesis of toxicity, some recent reports have shown that levodopa can have trophic effects on dopaminergic neurons in vitro, and our own work has shown that long term levodopa therapy promotes recovery of striatal dopaminergic markers in rats with moderate nigrostriatal lesions. Given that neither epidemiological nor clinical studies have ever provided evidence to support that long term levodopa administration can accelerate the progression of Parkinson's disease, we believe that levodopa therapy should not be delayed on the basis of an unconfirmed hypothesis.

The sydney multicentre study of Parkinson's disease: progression and mortality at 10 years

OBJECTIVES

To report on a 10 year follow up of patients with idiopathic Parkinson's disease, particularly with respect to mortality and the effect of early treatment with bromocriptine.

METHODS

The patients are from the 149 new patients recruited for a double blind, randomised study of low dose levodopa-carbidopa versus low dose bromocriptine. Patients were examined neurologically at least yearly. Neuropsychological examinations were performed at 0, 3, 5, and 10 years. Mortality and cause of death in these patients were compared with the Australian population using standardised mortality ratios (SMRs). Mortality and disease progression were compared by sex and treatment group. Predictors of death within 10 years, nursing home admission, and progression in Columbia score of >/=20 points were examined by logistic regression analysis.

RESULTS

Thirteen patients were excluded as having atypical Parkinsonism and six were lost to follow up. All available patients have been followed up for 10 years. Fifty patients (38%) were dead by 10 years and 63 by the last follow up. The SMR was 1.58 for all patients (p<0. 001). There was no significant difference in SMRs between the sexes. The mean duration of disease until death was 9.1 years. Parkinson's disease was thought to have contributed substantially to the death of 30 patients. The most common cause of death was pneumonia. Women progressed at a similar rate to men until 8 years, when the severity of their disease as measured by Hoehn and Yahr stage became greater (p<0.05). Older age of onset correlated with increased risk of death but the SMR was increased even in those aged <70 years (SMR 1.80, p=0.03). Early use of bromocriptine did not reduce mortality or slow progression of disease. One quarter of all patients had been admitted to nursing homes by 10 years. Only four patients were still employed.

CONCLUSIONS

Mortality in Parkinson's disease remains increased despite low dose levodopa-carbidopa therapy and no additional benefit was gained from early use of bromocriptine. Duration of disease was similar to that in the era before levodopa.

Chronic levodopa is not toxic for remaining dopamine neurons, but instead promotes their recovery, in rats with moderate nigrostriatal lesions

Orally administered levodopa remains the most effective symptomatic treatment for Parkinson's disease (PD). The introduction of levodopa therapy is often delayed, however, because of the fear that it might be toxic for the remaining dopaminergic neurons and, thus, accelerate the deterioration of patients. However, in vivo evidence of levodopa toxicity is scarce. We have evaluated the effects of a 6-month oral levodopa treatment on several dopaminergic markers, in rats with moderate or severe 6-hydroxydopamine-induced lesions of mesencephalic dopamine neurons and sham-lesioned animals. Counts of tyrosine hydroxylase (TH)-immunoreactive neurons in the substantia nigra and ventral tegmental area showed no significant difference between levodopa-treated and vehicle-treated rats. In addition, for rats of the sham-lesioned and severely lesioned groups, immunoradiolabeling for TH, the dopamine transporter (DAT), and the vesicular monoamine transporter (VMAT2) at the striatal level was not significantly different between rats treated with levodopa or vehicle. It was unexpected that quantification of immunoautoradiograms showed a partial recovery of all three dopaminergic markers (TH, DAT, and VMAT2) in the denervated territories of the striatum of moderately lesioned rats receiving levodopa. Furthermore, the density of TH-positive fibers observed in moderately lesioned rats was higher in those treated chronically with levodopa than in those receiving vehicle. Last, that chronic levodopa administration reversed the up-regulation of D2 dopamine receptors seen in severely lesioned rats provided evidence that levodopa reached a biologically active concentration at the basal ganglia. Our results demonstrate that a pharmacologically effective 6-month oral levodopa treatment is not toxic for remaining dopamine neurons in a rat model of PD but instead promotes the recovery of striatal innervation in rats with partial lesions.

Mortality in a population-based cohort of patients treated with antiparkinsonian drugs

OBJECTIVES

A number of studies have been focused on the mortality of parkinsonian patients, as compared with the rest of the population. In these studies, a mortality greater than expected on the basis of mortality of the general population has been shown. Nevertheless, just a few of these studies have investigated in detail the specific causes of death, probably as a consequence of both small cohort sizes and a short time period of observation. The aim of this study was to estimate cause-specific mortality in a cohort of patients treated with antiparkinsonian drugs.

METHODS

The study was performed on a wide population-based cohort of patients identified and followed-up through the computerized health databases of the Italian province of Rome (about 3,800,000 inhabitants). The follow-up lasted from January 1987 to December 1994. Standardized Mortality Ratios (SMR) were calculated for each specific cause of death, using the Rome province population as reference.

RESULTS

A cohort of 10,322 subjects, receiving antiparkinsonian drugs, were identified. There were 4328 deaths on an average follow-up of 5.7 years. This figure was 17% higher than was expected. A gradual decrease in SMR was observed in the oldest age groups. Statistically significant (95%) excesses of death were related to the nervous system (SMR = 1037; 95% CI 964-1110), mental disorders (SMR = 182; 95% CI 129-246), and endocrine and metabolic diseases (SMR = 117; 95% CI 102-133). Lower than expected mortality was found to be caused by malignant neoplasms (SMR = 56; 95% CI 51-61).

CONCLUSIONS

Apart from deaths specifically related to Parkinson's disease, the main differences between our cohort of patients and the general population were related to mortality due to malignant neoplasms and mental disorders. The gradual decrease in SMR for the oldest age groups, seems to indicate a greater reduction of life expectancy for patients with early onset of symptoms. This age-related trend could explain the relatively small excess of mortality, as in our cohort the median age of patients at entry was 74 years.

Treatment of early Parkinson's disease: are complicated strategies justified?

A variety of medical treatment strategies have been proposed as a means of slowing the progression of Parkinson's disease. This includes administration of selegiline (deprenyl) therapy, early use of bromocriptine or pergolide, and delay of levodopa therapy or restriction of the dose. There is no compelling evidence supporting the use of any of these treatment strategies for this purpose. Carbidopa-levodopa remains the most potent medication for symptomatic treatment of Parkinson's disease. Although starting levodopa therapy with the controlled-release formulation is advocated, this does not appear to have any major advantages over standard carbidopa-levodopa. Further studies are needed to identify other means of halting the progression of Parkinson's disease.

Does levodopa therapy delay death in Parkinson's disease? A review of the evidence

Studies examining the mortality from Parkinson's disease have been reviewed to assess the impact of levodopa therapy. These include national mortality data taken from death certificate returns, cohort studies comparing the deaths observed in a group of patients with those expected from population statistics, and case-control studies comparing deaths in patients with those in a matched control group. It is concluded that the decrease in crude mortality rate in the early 1970s in several western countries was mirrored by a decrease in observed to expected mortality rates in cohort studies over the same period. The rise in crude mortality in the late 1970s and early 1980s paralleled an increase in observed to expected mortality in cohort studies. These trends are compatible with the hypothesis that levodopa delayed the death of a cohort of frail elderly parkinsonian patients who succumbed approximately 5 years later, leading to an apparent "catch-up" increment in national mortality data. Whilst crude mortality in England and Wales does not appear to be increasing as fast as before the introduction of levodopa, recent cohort and case-control studies report mortality ratios comparable to those seen in the prelevodopa era. Further case-control studies are required to determine the position with current treatment regimens.

Survival and cause of death in a cohort of patients with parkinsonism: possible clues to aetiology?

Most previous studies that have examined the survival of patients with parkinsonism have recruited them from specialist centres. No previous study has ever reported cause specific mortality. We report on the mortality of a cohort of 220 parkinsonian patients recruited between 1970 and 1972 from 40 primary health care practices all over England and Wales and matched to 421 controls. At 20 years of follow up, 195 cases (88.6%) and 295 controls (70.1%) were no longer alive (P < 0.001). The median age at death for cases was 77.6 (range 53.8-97.3) and 83.5 (range 55.0-100.1) for controls (P < 0.001). The all cause hazard ratio for cases compared with controls was 2.6 (95% confidence interval (95% CI) 2.2-3.2) controlling for age, sex, and geographical region. There was little difference between men and women. Differences for cause specific mortality also emerged. Both ischemic heart disease (2.3, 95% CI 1.5-3.4) and cerebrovascular disease (3.6, 95% CI 2.2-6.1) showed significantly increased hazard ratios. Possible reasons for these findings are discussed in terms of (a) competing causes of death, (b) a secondary effect of drug treatment, and (c) common aetiological factors for both parkinsonism and cardiovascular disease.

Effect of physical exercise on mortality in patients with Parkinson's disease

Public health nurses visited and followed up for more than one year 438 patients with Parkinson's disease living in Osaka. The follow-up period averaged 4.1 years, during which 71 deaths were observed. The patients were classified according to the degree of physical exercise they performed, and the ratios of observed to expected deaths were calculated. The exercising group showed the lowest ratio of 1.68 (1.45 for patients able to walk independently, and 1.89 for those could not) while all patients exhibited a ratio of 2.47. Multivariate analysis using Cox's proportional hazard model, adjusted for age, sex, walking ability and duration of disease at study entry, showed that, compared with the exercising group, the non-exercising patients had a hazard ratio of 1.83.

Is the prevalence of Parkinson's disease in New Zealand really changing?

The prevalence of idiopathic Parkinson's Disease (IPD) in Dunedin, New Zealand on 31st July 1990 was 110.4/100,000. When corrected to a standard population based on the 1960 U.S. census, the prevalence fell to 76.0/100,000 due to changes in the age structure of the population. The corrected prevalence in Wellington (another New Zealand city), in 1962 was 99.6 (before the introduction of levodopa), and in Aberdeen, Scotland in 1984 was 102.7. The principal difference was fewer people under 65 years of age in our study. Case finding methods and diagnostic criteria were similar in all three studies, and case ascertainment was adequate. Under representation of younger people could be due to either a lower incidence rate or poorer survival due to treatment with high doses of levodopa compounds. Prospective research is required to explain our findings.

Parkinson's disease in Aberdeen: survival after 3.5 years

The increasing age of the general population and of patients suffering from Parkinson's disease suggests that a reappraisal of mortality rates and factors related to increased mortality should be carried out. A 3.5 year follow-up of a whole population sample of 267 patients and 233 controls matched by age, sex and general practitioner, yielded a relative mortality rate of 2.35 (99%-confidence interval: 1.60-3.43). Factors predicting death within the follow-up period were: cognitive impairment, old age, late age of onset, long history of smoking, lower blood pressure, and a variety of signs, symptoms and sequelae of Parkinson's disease associated with decreased mobility. However, age less than 70 years, age of onset before 66 years, absence of kyphosis or normal Webster posture score, mild impairment on the Hoehn & Yahr scale (1-2), or no impairment in a 10-question mental status questionnaire (9-10), were not associated with an increased risk of death.

Multi-center study of Parkinson mortality with early versus later dopa treatment

Four geographically diverse centers provided data on mortality in 359 patients with Parkinson's disease, the majority of whom began dopa treatment during the early experimental trials of 1968 to 1970. Patients were classified into three groups based on the duration of symptoms prior to starting dopa treatment: Group 1, 1 to 3 years; Group 2, 4 to 6 years; Group 3, 7 to 9 years. After 15 years of treatment and 3,689 person-years of observation, Group 1 had an observed-to-expected mortality ratio of 1.43; Group 2, 2.44; and Group 3, 2.95 (p less than 0.05). This result confirmed that increased duration of disease was associated with increased mortality risk. To examine the effect of the time of initiation of dopa treatment, duration of disease was held constant at 17 years for all three groups. Observed-to-expected mortality ratios were 1.43 for Group 1; 2.66 for Group 2; 2.63 for Group 3. This statistically significant advantage for Group 1 (p less than 0.0001) led to the conclusion that early treatment with dopa has a beneficial effect on life expectancy. After 17 years of disease, causes of death in Group 1 were less likely (p = 0.027) to be due to Parkinson's disease than was found in the other groups.

Parkinsonism--drug treatment: Part I

The purpose of this two-part review is to explain current drug treatment in part I and discuss investigational drug therapy and miscellaneous drugs in the management of parkinsonism in part II. The medical approach to this disease is still based on the imbalance between a deficiency of dopamine and a functional increase in acetylcholine. Anticholinergic agents are used to treat the tremors in the early stages of the disease.

Carbidopa dosage modifies L-dopa induced side effects and blood levels of L-dopa and other amino acids in advanced parkinsonism

Thirty-four patients with advanced Parkinson's disease showing intolerance to therapeutic doses of L-DOPA were treated with L-DOPA plus carbidopa at two different proportions. Ten patients preferred medication containing 10% carbidopa while 24 preferred 25% carbidopa. The increase of carbidopa reduced gastrointestinal disturbances and psychiatric side effects related to L-DOPA, but improvement of disability when measured according to objective tests was modest. Higher doses of carbidopa reduced peripheral DOPA metabolism and increased blood levels of tryptophan, 3-OM-DOPA and DOPA in relation to the administered dose.

Effect of L-dopa on course of Parkinson's disease

A review of the progress of 176 patients with Parkinson's disease who were given maximum tolerated doses of L-dopa between November, 1969, and December, 1972, showed that the ratio of observed to expected deaths after 12 years' sustained therapy was 2.59 (2.14 for males and 3.64 for females). This contrasts with the overall 6-year follow-up figure for the same patients of 1.45 (1.29 for males and 1.85 for females). These findings indicate that although L-dopa may improve life expectancy during the first 6 years of therapy the protective effect subsequently declines.

Problems associated with long-term levodopa treatment of Parkinson's disease

Levodopa treatment improves significantly not only the parkinsonian disability but also the mortality rate. However, during long-term levodopa treatment the therapeutic benefit gradually declines. Furthermore, most cognitive skills improve initially, but long-term levodopa treatment is associated with declining intellectual capacity and dementia. In patients on long-term levodopa treatment there seems to be a low threshold for certain clinical side-effects, especially postural hypotension, psychiatric disturbances and various types of fluctuations in disability. Low age at onset of Parkinson's disease, and at the commencement of levodopa therapy, the duration of levodopa treatment and a high dose of levodopa seem to be significant risk factors for the development of response fluctuations, but not the pretreatment duration of Parkinson's disease nor the disability of the patients. A readjustment of the levodopa dosage, and as an adjuvant drug treatment, deprenyl, a specific inhibitor of MAO type B, or a direct-acting dopamine agonist may prove helpful in the management of fluctuations in disability. It is important, moreover, to try to prevent these phenomena by taking into account the predictive risk factors of response fluctuations in the treatment strategy of Parkinson's disease.

Diagnosis and epidemiology of Parkinson's disease

The diagnosis of Parkinson's disease is purely a clinical diagnosis. The most common types of diagnostic error are a failure either to recognize the early, or unusual symptoms, or to differentiate other tremors and extrapyramidal syndromes from Parkinson's disease. The prevalence of Parkinson's disease is increasing. This has resulted from the reduction of the excess mortality by levodopa treatment. In the near future, there will be more older parkinsonian patients with a more prolonged duration of the disease.

The management of Parkinson's disease

It is useful to divide Parkinsonian patients into those whose signs are confined to tremor, rigidity and akinesia, and those with evidence of a more diffuse disturbance. The treatment of choice in the former is levodopa combined with a peripheral decarboxylase inhibitor. At the onset of the disease, when disability is minimal, amantadine or anticholinergic drugs may suffice. Bromocriptine is useful in some patients who derive only short-lived benefit from each dose of levodopa. The role of stereotactic surgery is now confined to patients with an incapacitating unilateral tremor which has not improved with drug therapy. In elderly patients with evidence of diffuse cerebral dysfunction such as dementia, grasp reflex, hyper-reflexia or severe postural hypotension, the beneficial effect of these drugs is often outweighed by the side effects. Small doses of levodopa alone may be tried. Anticholinergic drugs and amantadine should be avoided in such patients.

Epidemiology of Parkinson's disease--an overview

Among the white races, the prevalence rates of Parkinson's disease range from 66 to 187 per 100,000 population, through without any obvious geographical pattern. A similar variation is found in the annual incidence rates with estimates from 5 to 24 per 100,000 population. The black races may be partially protected against the disease. Both sexes are probably equally affected by the disease. Parkinson's disease usually begins after the age of 50 years, and the risk of the disease steeply rises with advancing age. Parkinson's disease is often omitted in death certificates; mortality rates with Parkinson's disease as an underlying cause of death vary from 0.5 to 3.8 per 100,000. Levodopa treatment, by reducing the excess mortality accompanying the natural course of Parkinson's disease, may increase the number of patients living with this disease in the near future. Postencephalitic Parkinson's disease, developing as a sequel to lethargic encephalitis and accounting for some two thirds of parkinsonian cases shortly after the epidemic, has probably been a transient phase in the epidemiology of Parkinson's disease and is now disappearing. Data from epidemiological investigations have advanced our understanding of the cause of Parkinson's disease only to a small extent. No other characteristic than race has been found to influence the susceptibility to the disease. The environmental risks for Parkinson's disease have not been unequivocally demonstrated. Highly conflicting information is available as to the contribution of hereditary to the pathogenesis of Parkinson's disease. Seroepidemiological investigations have shown an increased antibody response against herpes simplex virus in parkinsonian patients, but attempts to detect herpes virus specific products or DNA sequences in the brain material have been unsuccessful.

Treatment of Parkinson's disease: problems with a progressing disease

Long-term follow-up of parkinsonian patients has shown that although levodopa treatment significantly improves the parkinsonian symptoms and the quality of life of parkinsonian patients for several years, various distressing difficulties arise during chronic levodopa treatment, such as the loss of benefit, dyskinesias, on-off phenomena, postural instability and dementia. Clinical, neuropsychological, mortality and post-mortem brain studies indicate that levodopa as a replacement therapy does not modify the progression of the underlying pathology and the natural course of the disease. It seems that levodopa has only a limited period of optimal usefulness in the treatment of Parkinson's disease. However, at present there is no better or more potent therapeutic agent available than levodopa and it is still the primary treatment of Parkinson's disease. It would be reasonable not to begin levodopa treatment in patients with mild symptoms but to withhold levodopa until the severity of symptoms really makes its use necessary. Thus it is possible to get the maximal long functional benefit. Post-mortem brain studies have shown that in Parkinson's disease there is not only a progressive loss of dopaminergic substantia nigra neurons but there are also significant changes in the striatal dopamine receptors. In some patients a denervation supersensitivity seems to develop and in some others a loss of dopamine receptors in the striatum. However, in advanced parkinsonian patients with a deteriorating response to levodopa, there seem to be still enough dopamine receptors in the striatum for drugs stimulating the dopamine receptors directly to improve the parkinsonian disability. Indeed, recent evidence indicates that dopaminergic agonists, such as bromocriptine, seem to be a significant and valuable adjuvant therapy to levodopa in parkinsonian patients with a deteriorating response and/or the on-off phenomena. Although bromocriptine is not completely satisfactory, it is a significant opening to a new mode of treatment. In the future it will be very important to develop more potent and selective dopaminergic agonists affecting only those striatal receptors which are mainly responsible for the parkinsonian symptoms. Then a better therapeutic response is likely to occur and many central side effects can be avoided. Current difficulties in the management of Parkinson's disease greatly depend on the fact that we are dealing with a symptomatic therapy. It is hoped that future research will soon lead to a discovery of the primary cause and consequently to a causal therapy of Parkinson's disease.

Changing epidemiology of Parkinson's disease: predicted effects of levodopa treatment

Recent studies suggest that levodopa treatment reduces the excess mortality due to Parkinson's disease, found to be three times that expected in the general population. This will affect the equilibrium state of the epidemiology of Parkinson's disease. The predicted increase in prevalence of Parkinson's disease was calculated according to two mortality patterns, one the same as expected in the general population and the other 1.5 times that expected; the proportional increase in prevalence is 1.8 and 1.4, respectively. The predicted increase in the duration of the disease if 6.3 or 3.2 years. As a consequence, there will be an increase of patients with long-term levodopa treatment difficulties, and with Parkinson's disease symptoms not treatable with levodopa, e.g. dementia. This seriously warrants the research of new approaches in the treatment of Parkinson's disease.