The experience of Ed. Müller in Hesse-Nassau was that not less than 96 per cent. of the total cases occurred within the first decade. Children over five years of age were relatively seldom affected: nine tenths of the cases occurred in those less than five years old. The disease incidence was markedly greatest in the latter half of the second year. Cases in the second or third decade were quite exceptional. Of seventy-six sporadic cases collected by Byrom Bramwell, forty-one occurred between 0 and 3 years; eighteen between 3 and 6; four between 6 and 9; one between 9 and 12; and four between 12 and 15; five were over 15; and in three the age was not ascertainable.
Heine-Medin's disease is therefore principally a disease of childhood. Celebrated writers have even stated that acute poliomyelitis does not occur in adults. But the statistics of Wickman and Leegaard, however, show that adults are by no means immune. Fr. Schultze, Rissler, Taylor, van Gehuchten, Wickman and others had already by pathologic anatomic examinations proved that the disease affects adults. Wickman saw a man of 46 years suffering from a typical attack, while his nine children living in the same house with him remained unaffected. It is possible that conditions change from epidemic to epidemic, so that the frequency of attacks upon adults varies. On the other hand, the great diversity of existing statements upon this point may partly be due to a lack of uniformity in the thoroughness of the reports.
Besides the age, no other predisposing factor is positively known to us. As regards sex, the cases during the various epidemics, of which I have data, occurred as follows:
| Male | Female | Total | |
| Medin (1887) | 22 | 22 | 44 |
| Medin (1895) | 15 | 6 | 21 |
| Leegaard (1899) | 31 | 23 | 54 |
| Wickman (1899) | 33 | 21 | 54 |
| Wickman (1903) | 8 | 10 | 18 |
| Wickman (1905) | 591 | 426 | 1,047 |
| Leegaard (1905) | 472 | 365 | 837 |
| Zapport (1908) | 130 | 97 | 227 |
| Lindner and Mally (1908) | 57 | 37 | 94 |
| Lovett (1907) | 131 | 103 | 234 |
| Lovett (1908) | 39 | 26 | 65 |
| Emerson (1908) | 42 | 47 | 100 |
| Ed Müller (1909) | 53 | 4 | 100 |
