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Estimation of survival in Spinocerebellar Ataxia type 2 Cuban patients
Author(s) -
AlmaguerMederos LE,
Aguilera Rodríguez R,
González Zaldivar Y,
Almaguer Gotay D,
Cuello Almarales D,
Laffita Mesa J,
Vázquez Mojena Y,
Zayas Feria P,
Auburger G,
Gispert S,
Velásquez Pérez L
Publication year - 2013
Publication title -
clinical genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 102
eISSN - 1399-0004
pISSN - 0009-9163
DOI - 10.1111/j.1399-0004.2012.01902.x
Subject(s) - spinocerebellar ataxia , rehabilitation , ataxia , medicine , pediatrics , physical therapy , psychiatry
To the Editor : Spinocerebellar Ataxia type 2 (SCA2) is a neurodegenerative disorder that reaches the world’s highest prevalence in Holguín, Cuba (1). Despite the early morbidity and mortality of SCA2, there are insufficient data assessing the affect of the disease on patient survival. Here, we make use of this large sample of affected SCA2 families to evaluate disease and expanded CAG repeat number impacts on patient survival. Clinical and molecular data were obtained in the course of a nationwide survey for SCA2 families (1). The protocol was approved by the institutional board and an informed consent was obtained from each participant. A dataset was assembled consisting of two age and sex matched groups: affected individuals with molecular and clinical diagnosis whose age at death or current age could be established (n = 606, 53.3% male), and unaffected non-carrier siblings (n = 614, 47.6% male). All individuals were born between 1915 and 1991. In the affected group the age at onset had a mean of 30.3 ± 14.1 years. Corresponding figures for overall survival – years from birth to death – and survival after disease onset – years from onset to death – were 52.0 ± 17.7 and 21.8 ± 9.3 years, respectively. The expanded CAG repeat varied between 32 and 79 with a mean of 41.4 ± 5.7 units. The diagnosis was made on the basis of clinical examination and molecular testing (1). Data were processed by the Kaplan–Meier method, log-rank statistics and Cox regression. Statistics were computed in SPSS software (2). There were 177 deaths among the 606 SCA2 affected individuals (429 censored), and 23 events among their 614 unaffected siblings (591 censored). Expected survival estimates for the affected and unaffected individuals are show in Table 1. The median overall survival estimate for the affected individuals was lower than that obtained for unaffected individuals (Table 1). The survival curves corresponding to the affected and unaffected groups were significantly different from each other as a whole and by sex (Fig. 1). There were no significant differences for survival curves between male and female in the affected and unaffected groups (p > 0.70). No comparison between survivals in SCA2 affected individuals and in unaffected relatives has ever been reported, and even survival estimates for SCA2 patients were limited by the small number of individuals tested (3, 4). Previous studies overestimate the effect of SCA2 Fig. 1. Overall survival curves by clinical status and sex as assessed by Kaplan–Meier analysis. Survival probabilities were significantly lower in SCA2 affected individuals as compared with their unaffected siblings (log-rank test, p < 0.001).