Prevalence of Parkinson’s Disease: Africa

31 Dec
2009

Of the 750 inpatient and outpatient cases which Harries had seen in his neurology practice in Kenya over a five-year period, he observed 27 cases of PD (-4% of neurology patients) with an age range of 45-60 years. A survey of patients admitted to the hospital over a one-year period in what was formerly known as Rhodesia revealed three patients with a diagnosis of PD, accounting for less than 1% of all neurological admissions. Both these percentages were similar to those reported by Haddock in Ghana among 280 admissions and 192 outpatients. Col-lomb who saw inpatients and outpatients over a 10-year period in Senegal also reported that less than 1% of neurological admissions were due to PD. Interestingly, his observations of outpatients over time suggested that among patients with classical PD in 25% of cases, the disease seemed to progress more slowly in comparison to his previous clinical experience in England. Conversely, Cosnett’s experience in Natal (South Africa) led him to conclude that though Parkinsonism was common, true PD was rare. For his summary on Nigerian patients, Osuntokun reviewed 13 years of records and found 107 cases of Parkinsonian syndrome (1% of neurological admissions). He observed that the peak incidence was in sixth decade and commented that liver disease was the cause of many of the early-onset cases. A later study by the South African neurologists Cosnett and Bill involved reviewing records from all patients seen for neurological consultation during a seven-year period (1979-1985). Patients with Parkinsonian symptoms were classified as having PD or Secondary Parkinsonism (SP). They found PD in 0.15% of blacks and 2.3% of whites, whereas SP occurred in 0.5% of blacks and 1.15% of whites. Interesting is the fact that only 22.8% of black patients were over the age of 50 as opposed to 47.8% of white patients.

Osuntokun et al. also did a later retrospective review of records. He reported seeing 217 patients with Parkinsonism in his neurology clinic over a 10-year period (1966-1976). Mean age of onset for idiopathic PD was 55.6 years, and it is particularly noteworthy that two patients with idiopathic PD volunteered a positive family history.
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Lombard and Gelfand conducted a retrospective survey of cases admitted with PD to Harare Hospital in Zimbabwe between 1973-1976 and compared them with the European admissions to Andrew Fleming Hospital in the same city between 1974 and 1976. Out of 82,000 admissions in a four-year period to Harare Hospital, 17 cases of PD were reported. This was significantly lower than the 33 cases that were seen in almost 35,000 patients admitted to Andrew Fleming Hospital.

Studies among Outpatients (United States)

Convinced that the approach of identifying patients through hospital admissions was limited, Kessler set about attempting to ascertain PD cases through neurologists and general health providers in the community within Baltimore. In this study, a random sample of 6% of physicians in the community, of whom 25% were neurologists, were invited to be members of a PD panel. They were asked to register all patients that they had diagnosed with PD between 1967 and 1969 based on the four diagnostic criteria: tremor, rigidity, slowness, and immobility of the facies. Differences in incidence figures were seen, as they found 31 and 8.7 cases/100,000 in black men and women, respectively, as compared with 128 and 121 in white men and women. Such a study design, however, is open to ascertainment bias since socioeconomic factors could effect the likelihood that an African-American with symptoms of PD might seek out specialists in neurology most capable of making the diagnosis of PD. Furthermore, there is a documented reluctance among African Americans and African-American physicians to participate in clinical research, which, though understandable, could also lead to serious under-reporting of PD among African Americans. cialis canadian pharmacy

In a separate study of two New York districts, Mayeux et al. counted all individuals with a diagnosis of PD who either had sought medical services at hospitals and doctors offices or had requested medical assistance from federal and state agencies between 1988-1993. All individuals they identified were subsequently examined by a neurologist and only deemed to be affected if they had the necessary diagnostic criteria of bradykinesia and at least one other feature (muscular rigidity, resting tremor, or postural instability). Additional criteria included the presence of at least three of the following: history of unilateral onset, persistence of asymmetry of symptoms, history of improvement on levodopa, a progressive course or a history of levodopa-induced chorea. As there were clear diagnostic criteria for this study and every individual with a suspected diagnosis was examined by a neurologist, the diagnosis was clearly confirmed in individuals reported as affected. They reported a total prevalence rate of 107 per 100,000 and an average annual incidence of 13 per 100,000. Age-adjusted prevalence rates were lower for blacks (92 men and 55 women per 100,000) than for whites (172 men and 86 women) and Hispanics (187 men and 95 women). As comparable prevalence figures were seen in whites and Hispanics, socioeconomic factors and access to medical care were thought unlikely to account for the lower prevalence observed in blacks. The researchers speculated that the apparently reduced prevalence in the black population was a function of reduced survival, as the number of deaths in the incident cohort was significantly greater for blacks than for any other ethnic group. However, the study by Mayeux et al. also found that black men over age of 75 years had the highest incidence rate of any group. It is therefore possible that the age of onset or age at diagnosis was delayed in this group. The reasons for such a delay are unknown and could include biological, economic, or social factors, acting alone or in combination. As with the hospital-based studies, both of these large community-based studies required that individuals were seeking medical care and, in the case of the latter study, already carried a diagnosis of PD.

The Harlem Aging Project involved interviewing about their health status a probability sample of 164 elderly persons—65 years of age or over and living in central Harlem. Approximately, 97% identified themselves as black. Cognitive screening measure assessed cognitive functioning, neurological signs associated with PD or stroke, communication, ambulation, and mood. Nonmedical interviewers trained to conduct the survey administered the questionnaire but there were no follow-up exams by neurologists. Only 0.6% had received the diagnosis of PD, but 16.2% of the sample had three or more symptoms of PD; 7.5% had four or more symptoms. As neurologists were not involved in ascertainment or confirmation, the sensitivity and specificity of this study cannot be assessed. However, the results do suggest under-reporting of Parkinsonism.

Most recently, the incidence of PD was ascertained in patients followed at the Kaiser Permanente Medical Care Program of Northern California. The population was representative of the general population in terms of race but had above average income and higher education levels than the general population. Clinical summaries were abstracted from the medical records by medical record analysts, and neurologists reviewed these summaries to ensure that the essential diagnostic criteria were present. No clinical examinations were performed to confirm reported symptoms. Although not statistically significant, these researchers did observe fewer cases of PD in blacks (10.2/100,000) than in non-Hispanic whites (13.6/100,000).

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