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A Case-Control Study in the Azores (Portugal)

Manuela Lima, PhD; Paula Coutinho, MD, PhD; Augusto Abade, PhD; João Vasconcelos, MD; Francine M. Mayer, PhD

Arch Neurol. 1998;55:1341-1344.

Background  Machado-Joseph disease (MJD) is an autosomal dominant cerebellar ataxia of adult onset with a high prevalence in the islands of Azores (Portugal). The genetic epidemiological studies presently under way in these islands are based on the genealogical reconstruction of the affected families, thus partially depending on the reference of patients using family history. A considerable effort has been made to obtain genealogies that are as complete as possible, making use of different types of data. The utility of the death causes contained in the death registers of the patients with MJD was determined in this study.

Objectives  To estimate the extent to which the cause of death reported in the death register can confirm other reports of an individual's status for the disease (ie, oral information), and to determine the accuracy of the death certificates in listing MJD in patients whose disease was clinically diagnosed.

Design  Case-control study.

Methods  The death registers of 113 patients with MJD (82 whose disease was identified by history and 31 whose disease was clinically diagnosed) were examined and compared with those of controls matched by sex and date and place of death.

Results  There were significant differences in the causes of death between cases and controls, both for those whose disease was identified by history (²=51.69, P <.001) and for those whose disease was identified by examination (²=27.78, P =.004). However, the cause of death was in accord with the presence of the disease in only 40% of the cases reported as being identified only by family history. In the cases in which the disease was clinically diagnosed, only nearly 38% of the registers provided reliable information as to MJD being the direct cause of death.

Conclusions  The fact that only nearly 40% of the patients with clinically confirmed MJD had a cause of death compatible with MJD precludes the use of cause of death as a means of identifying affected individuals in the Azorean MJD pedigrees.

From the Department of Biology, University of the Azores (Dr Lima), and the Department of Neurology, Hospital of Ponta Delgada (Dr Vasconcelos), Azores, Portugal; the Department of Neurology, Hospital of Santo Antonio, Porto, Portugal (Dr Coutinho); the Department of Anthropology, University of Coimbra, Coimbra, Portugal (Dr Abade); and the Department of Biological Sciences, University of Quebec in Montreal (Dr Mayer).