All of the parkinsonism variants limit mobility, and the increased tendency for falls and dysphagia predisposes these patients to life-threatening complications (33,34). Life expectancy prior to the widespread use of levodopa was significantly reduced.
In one hospital based parkinsonism series during the 1950s and 1960s, the mean survival after onset was 10.8 years (35). Excluding postencephalitic parkinsonism, the mean survival was 9.42 years, which is frequently cited as the yardstick for the prelevodopa era life expectancy (35). Mean survival in the contemporary parkinsonism cases cannot be compared with that study. There have been significant social and health care advances leading to longer life in the general population, and one would expect that parkinsonism patients would share these survival gains. Comparisons for survival should be made matching for year of birth, gender, and region/country.
Kurtzke et al. (36) noted that patients in the 1980s were, on an average, five years older at death than those who died in the 1970s—implying that life expectancy since the widespread use of levodopa has increased by five years. Several other studies (37-40) have also reported longer life expectancy, but it is still lower than expected. At the other extreme are studies (41,42) that suggest that current parkinsonism cases survive longer than the general population. It is difficult to reconcile that individuals suffering from a progressively disabling disorder would live longer than the matched general population. The most common error in the better than expected survival studies is measuring survival from the date of onset assigned several years retrospectively. During that period, the general population would have suffered some death. That gives the parkinsonism group an artificial advantage since they survived at least to diagnosis (41). When we assessed our patients using the date of onset, the parkin-sonian patients had greater survival than the general population (40). The other reason for this error is inclusion of only the levodopa-treated cases (42). For any number of reasons, some patients may not be treated with levodopa, and those destined for longer survival may be treated with levodopa introducing significant bias. Researchers noted that survival is greater if only the levodopa-treated cases were considered (17). Restricting a study to only clinically diagnosed PD and excluding other variants introduces another source of bias as the inaccuracy of clinical diagnosis is well known (8,9) and survival is shorter in non-PD variants (10,43,44).
Ablinded study withholding modern drugs from one group of matched patients is unethical and therefore not possible. In our clinic-based study of 934 parkinson-ian cases seen between 1968 and 1990, survival measured from the date of first assessment was significantly reduced (P< 0.0001) (45). As of 1974, patients in this clinic had widespread and easy access to levodopa. Prelevodopa era reduction in survival was even more pronounced. Taken together, these indicate that widespread use of lev-odopa has improved survival. The timing of treatment with levodopa indicates that survival benefit is achieved only when the patients are treated prior to the loss of postural reflexes—Hoehn and Yahr stage III (35). Others reported similar observations of longer survival in patients with early levodopa treatment (38). It is evident that the survival gap between the current parkinsonian cases and the general population has narrowed. This gain in life expectancy is attributable exclusively to the better symptomatic control with levodopa that reduces disability and life-threatening complications (33,34). We estimate that an average patient with PD onset at age 62 now lives for approximately 20 years.
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