Effect of climatic temperature on the age of onset of Huntington's chorea.

The age of 1,403 subjects at onset of Huntington's chorea were drawn from the literature and related to the mean annual, January, and July temperatures of their place of residence. When the data were converted into mean annual, winter, and summer isotherms covering a range of 10° F (5·6° C), there was a statistically significant decrease in age of onset as the temperature increased. Over the ranges studied, winter temperatures exerted a stronger effect than summer temperatures. To reduce interference by ethnic factors, the analysis was repeated on North American subjects with similar results. It is suggested that repeated infections may provoke chorea and that the observed lowering of the age of onset is associated with increased susceptibility to infection on passing from cold to warm climates.