Two different types of cellular phones were included in the study: the portable model where the antenna is located together with the battery in a box separately from the hand piece, and the handheld model which has the antenna in the hand piece in close proximity to the head during a call.
|Group 1||portable cellular telephone users|
|Group 2||handheld mobile telephone users|
23 % of the customers had a handheld mobile phone, 19 % had a portable mobile phone; telephone type was unknown for the remaining 58 %. 604 deaths occurred among the cohort members during 1994. The overall mortality rates for portable and handheld cellular phone users were similar and much lower than corresponding rates for the general population. The low mortality probably reflects the higher socioeconomic status of cellular phone customers.
A substantial proportion of the original cohort had to be excluded due to missing information. The time between exposure to cellular phones and the death endpoints was short, so the study addressed only short-term effects.