Acute myeloid leukaemia affects all ages, but only abut 25% of cases occur in people under the age of 25 years. There is an exponential rise in incidence above the ages of 40 years. The average age of onset is about 65 years. The incidence is slightly higher in males than females. American studies have shown a higher incidence of one subtype called promyelocytic leukaemia (APL) in people of Hispanic descent.