Motor neuron disease and multiple sclerosis mortality in Australia, New Zealand and South Africa compared with England and Wales.

There has been a marked increase in the reported mortality from motor neuron disease (MND) but not multiple sclerosis (MS) in England and Wales and in a number of other countries. A comparison has been made of the mortality from MND and from MS for two time periods in Australia, New Zealand and South Africa. An increase in MND mortality occurred in Australia and New Zealand between 1968-77 and 1978-87, greater than that which occurred in England and Wales, but there was no increase in MS mortality. Among the white population of South Africa, the MND mortality was half of that in England and Wales, Australia and New Zealand in both time periods. Both MND and MS mortality is higher in the English-speaking than in the Afrikaans-speaking white South African-born. The marked increase in MND mortality which has now been reported from many countries, is good evidence that an environmental factor is important in causing this disease. The large differences in MND mortality in different populations may be important clues to the environment factors causing the disease.