In total, 384 cassava/corn millers were recruited (including 1
woman), and among them, 365 male millers were eligible (exposed
group). Three hundred and sixty-five civil workers (nonexposed
group) without exposure to vibration were recruited from a population
of 446 civil workers from local public offices (Fig. 1). They
were local provincial government office workers. The office
workers matched to the millers were those involved only in office
work (typewriting, computer work, secretarial and reception services).
A large majority of millers were age-matched to nonexposed