Prevalence of Parkinson’s Disease

30 Dec
2009

Parkinsonism

INTRODUCTION

Parkinson’s disease (PD) is a common progressive neurodegenerative disorder characterized clinically by bradykinesia, resting tremor, rigidity, and postural instability. Symptomatic response to L-DOPA therapy is also often used as an additional diagnostic criterion. It affects 1-2% of the population over the age of 60 years, although the disease is seen in younger individuals as well. A recent meta-analysis of studies to date suggests an overall annual incidence of 16-19/100,000. In 1993, a review of the worldwide occurrence of PD reported that Asian and black African populations have the lowest prevalence rates of this disease in the world. Reports to date have not only suggested that the prevalence rate is lower in black Africans but, in addition, that this rate is also lower in African Americans as compared to Caucasians. We have noted a deficiency of black families among volunteers for our ongoing studies on the genetics of PD. We, therefore, undertook a literature review in order to ascertain whether a reduced prevalence of PD among African Americans might be a contributing factor to there being fewer black individuals and families affected with PD in our study.

BACKGROUND

Most studies to date have focused on the prevalence as opposed to the incidence of PD. As prevalence is a function of both incidence and survival, the reduced average life expectancy among African Americans as compared to white Americans could result in a significant inherent limitation of any measurement of prevalence of a disease affecting a predominantly older population. Most studies have examined the prevalence of PD through review of hospital records, physician registration, and review of death certificates. There have only been three community-based studies published to date: two door-to-door studies that looked at African and African-American populations in Nigeria and Mississippi, respectively, and one study that examined the prevalence of the disease in different racial groups enrolled in a health maintenance organization in California. A synopsis of the studies to date is presented below. canada pharmacy mall

Studies among Hospital Inpatients (United States)

The first study ascertaining individuals affected with PD through hospital admission records was published in 1972. In this study, Kessler looked at all patients discharged with a diagnosis of PD or Parkinsonism from all Baltimore hospitals between 1965 and 1967. A physician without specialty training in neurology reviewed the charts to confirm the diagnosis, and the study did not specify which diagnostic criteria were being used to confirm the diagnosis. It was not stated how many of the patients had been examined by a neurologist during their hospital stay, but only 20% of those identified as having PD had been admitted for problems related to PD. All individuals identified as having PD in this population were visited by an interviewer who was not medically trained, and they completed a questionnaire that included a number of questions pertaining to the diagnosis of PD, lifestyle factors, and other health conditions. They reported that PD/Parkinson-ism was significantly less common in blacks than in whites. The annual reported prevalence of 28 (per 100,000) in white males and 22.8 in white females was significantly higher than the 4.6 and 4.3 seen in black males and females, respectively. We do not know the ethnic, age, and gender breakdown of the total hospital population during that period.

In another study, medical records were reviewed for patients admitted over a 10-year period (1959— 1969) to a charity hospital in New Orleans with a patient population that is 75% black. They only included patients with unequivocal clinical evidence of PD and found that it occurred in 0.022% of black patients as compared with 0.146% of whites. The ages of the populations were not given, but if consistent with the national survival rates at the time, it is likely that the average age of the patients was lower among the black population than the white. cialis professional 20 mg

The hospital-based studies do not address the differences in delivery and uptake of medical services between African Americans and whites. Without specialty training in neurology, interviewers would be far more likely to ascertain a patient with PD when the patient already knew he carried the diagnosis, having previously sought and received outpatient medical evaluation for neurological symptoms. It is also not apparent that a hospital setting is the best place to encounter patients with PD. In Kessler’s study, only 20% of patients with PD were admitted because of problems related to the disease, and it is likely that as treatments further improve in the future even fewer PD patients will be admitted with disease-related problems.

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