Therefore, results for these classes are presented in Tables 4 and 5 stratified by age. The risk of HL was elevated and showed evidence of a positive trend by number of acetylcholinesterase inhibitors used for the younger age group, but not in the older age group (ORs for two pesticides were 3.16 (95 % CI 1.02–9.29) for40 years and 0.49 (95 % CI 0.15–1.62) for [40 years).