Dynamics of parkinsonism-Parkinson's disease in residents of adjacent kibbutzim in Israel's Negev.

From serial studies of clinical findings and Webster's scores, we determined the incidence of Parkinson's disease and the pattern of progression of the components of parkinsonism in residents older than 40 in rural settlements with unusually high rates of Parkinson's disease in southern Israel (Negev). In 1988, the authors reported on three adjacent kibbutzim at which were identified 13 cases of Parkinson's disease in a population of 413 persons older than 50 years. In the region as a whole, there were 143 additional cases among a population of 64,185 who were 40 years of age or older. The age-standardized prevalence ratio for the kibbutz population was 5.43. By 1993, 2 of the persons with Parkinson's disease had died, and 8 new cases had been diagnosed. The age-standardized prevalence ratio in 1993 was 8.09. The crude incidence ratio for persons older than 40 was 3.4 per 1000 per year. Webster's score is used as an estimator of the severity of pre-parkinsonism. In the normal population of elderly persons from other areas in the Negev, only 20 of 110 had a score greater than 0 (11, 8, and 1 scored 1, 2, and 3, respectively). When the Webster's score was first applied systematically-in 1989 to asymptomatic persons from the kibbutzim who were older than 40-46 of 104 had scores of 2 or more, and some subjects also had impaired vibration sense. The tests were repeated by different observers on a casual sample in 1991 and 1993. Of the persons older than 60 in 1989 (n = 14), the scores increased from an average of 2.3 in 1989 to 3.9 in 1991 and to 5.7 in 1993. In a younger sample (n = 7), the mean scores were 2.3 in 1989, 3.6 in 1991, and 2.9 in 1993. These results are evidence of an age-specific peak in incidence and prevalence in the 70- to 79-year-old age group and may represent a cohort exposure phenomenon. The results may also reflect the critical role of age in the transformation of pre-parkinsonism to Parkinson's disease. Finally, in this population with high initial rates of Parkinson's disease, there was evidence of pre-parkinsonism in about half of those older than 40, and active progression of pre-parkinsonism in those older than 60. Therefore, this group is an ideal population to test for effects of preventive interventions.