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Huntington’s Disease Research Symposium

July 2005

Presented by Huntington's Research Group Victoria and Australian Huntington's Disease Association (Victoria)
2nd December, 2004 Conference Room, St George's Hospital, Kew, Victoria

Activity levels and age of onset in Huntington's Disease

In Huntington's disease (HD) the only proven factor to be related to onset age is the CAG repeat number, with longer repeat lengths associated with earlier average age of onset.

Nevertheless, this only explains 50-73% of the variation observed. An HD mouse model provides evidence for the protective effects of environmental stimulation. The aim of the present study was to identify and measure a series of environmental factors, including 'physical, intellectual and passive activity, occupation and education, to determine if they modify the age of symptom onset in HD.

Thirty participants with HD and a significant other completed two retrospective questionnaires. Diversity, intensity and percentage intensity of activities were calculated and linear regressions and ANCOVAs were used to investigate the correlation between these activity variables and age of onset while taking into account the effect of the CAG repeat length.

There was a significant negative correlation between passive percentage intensity of activity and age of onset in the teen years (partial correlation 0.615, R²=0.562, p=0.011), and in the early adulthood years (partial correlation 0.503, R²=0.399, p=0.047). This indicates that individuals who participated in high levels of passive activity presented with symptoms at a significantly earlier age than those with low passive activity (F(_1,15)=7.162, p=0.018).

Observed trends for physical and intellectual activity indicated that higher activity was associated with later onset although statistical significance was not reached.

This is the first direct evidence in humans that environmental factors are associated with timing of disease onset in HD and provides a potential intervention for those at risk. Important future studies based on this data include a retrospective study of a larger cohort and the implementation of a longitudinal prospective study of premorbid activity levels.

Zoe Horton¹, Veronica Collins¹, Ros Tassicker², Andrew Churchyard³ and Martin Delatycki^1,2
¹Bruce Lefroy Centre for Genetic Health Research
Murdoch Children's Research Institute, Victoria²
Genetic Health Services Victoria Huntington’s Disease Research Symposium