Back to Fertility Articles
Saturday 1st January, 2005
Laptops are positioned close to the scrotum, producing
direct local heat, and requiring the user to sit with his thighs close
with the scrotum between them.
US fertility experts warned teenage boys and young men to consider
limiting the time that they use laptop computers positioned on their
laps, as long-term use may affect their fertility.
The increasing popularity of laptop computers (LC), coupled with
existing evidence that elevated scrotal temperature can result in sperm
damage, prompted researchers from the State University of New York at
Stony Brook to undertake the first study into the effect of heat from LC
on scrotal temperature.
The findings are reported in Europe's leading reproductive medicine
journal Human Reproduction. They show that using an LC on the lap
increased the left scrotal temperature by a median 2.6?C and the right
by a median 2.8?C. Several previous studies have shown that increases in
testicular or scrotal temperatures of between 1?C and 2.9?C are
associated with a sustained and considerable negative effect on
spermatogenesis and fertility.
Lead researcher Dr Yefim Sheynkin, Associate Professor of Urology and
Director, Male Infertility and Microsurgery at the University, said: "By
2005, there will be 60 million laptop computers in use in the USA and a
predicted 150 million worldwide. Continued improvements in power, size
and price of LC have favored their increased use in younger people and
laptop sales now exceed those of desktop computers."
With the exception of an anecdotal report of genital burns, the
effect of portable computers on scrotal temperature when they are used
on the lap was not known, he said.
"Laptops can reach internal operating temperatures of over 70?C. They
are frequently positioned close to the scrotum, and as well as being
capable of producing direct local heat, they require the user to sit
with his thighs close together to balance the machine, which traps the
scrotum between the thighs."
The researchers worked with 29 healthy volunteers aged 21 to 35,
measuring scrotal temperatures with and without laptops. Two one-hour
sessions of scrotal temperature measurements were performed on different
days in the same room with a median room temperature of 22.28?C. The men
were dressed in the same casual clothing for each session and sessions
with and without LC were conducted at the same time of the day. Body
temperature was taken by mouth beforehand and each volunteer spent 15
minutes standing in the room to adjust to room temperature before being
seated. A non-working LC was placed on the lap so that the volunteer
could adopt the right position to balance the laptop, then removed, and
the seating position held for one hour, with scrotal temperature being
measured every three minutes. The same procedure was repeated for one
hour, with the same baselines controls, but this time with a working
laptop. The temperature of the bottom surface of the LC was also
measured at intervals.
Are you a doctor or a nurse?
Do you want to join the Doctors Lounge online medical community?
Participate in editorial activities (publish, peer review, edit) and
give a helping hand to the largest online community of patients.
Click on the link below to see the requirements:
Doctors Lounge Membership
"We found that scrotal temperatures rose by 2.1?C when the men sat with
their thighs together, which is necessary to keep LC on the lap. But,
the rise was significantly higher when the LC were used ? 2.8?C on the
right side and 2.6?C on the left," said Dr Sheynkin. " It shows that
scrotal hyperthermia is produced by both special body posture and local
heating effect of LC."
The median surface temperature of Pentium 4 computers used increased
from nearly 31?C at the start of the experiment to nearly 40?C after one
Dr Sheynkin said: "The body needs to maintain a proper testicular
temperature for normal sperm production and development
(spermatogenesis). Portable computers in a laptop position produce
scrotal hyperthermia by both the direct heating effect of the computer
and the sitting position necessary to balance the computer. The
magnitude of scrotal hyperthermia associated with abnormal
spermatogenesis is unclear. But, previous studies suggest that 1?C above
the baseline is the possible minimal thermal gradient capable of
inhibiting spermatogenesis and sperm concentration may be decreased by
40% per 1?C increment of median daytime scrotal temperature.
"We don't know the exact frequency and time of heat exposure capable
of producing reversible or irreversible changes in spermatogenesis.
Studies have shown significant but reversible changes after short-term
heating. However, LC produce significant repetitive transient scrotal
hyperthermia for years, and insufficient recovery time between heat
exposures may cause irreversible or partially reversible changes in male
"Portable computers in a
laptop position produce scrotal hyperthermia by both the direct
heating effect of the computer and the sitting position necessary to
balance the computer."
Dr Sheynkin said his team now planned further studies to evaluate the
heating effect of LC on testicular function and sperm parameters. For
now, he did not know an exact time for safe use. However, their study
showed that within the first 15 minutes of use scrotal temperatures
increased by 1?C, so it did not take long to reach a point that may
affect testicular function. Also, frequent use may cause intermittent
temperature rises, which could significantly increase a single heating
"Until further studies provide more information on this type of
thermal exposure", he said, "teenage boys and young men may consider
limiting their use of LC on their laps, as long-term use may have a
detrimental effect on their reproductive health."
Dr Sheynkin added that two LC brands were tested randomly to avoid
criticism that brands may differ. "All laptop computers generate
significant heat due to the increasing power requirements of computer
chips. New laptops with higher power requirements may produce even more
heat. So far, computer fans and 'heat sinks' are not sufficient. It's
possible that external protective devices could somewhat help, but it is
essential to confirm their protective effect in a clinical study to
prevent commercial advertising and use of inefficient and useless
European Society for Human Reproduction and