Hum. Reprod. Advance Access published December 9, 2004
Increase in scrotal temperature in laptop computer users
Yefim Sheynkin1,2, Michael Jung1, Peter Yoo1, David Schulsinger1 and Eugene Komaroff3
1Department of Urology and 3General Clinical Research Center, State University of New York at Stony Brook, Stony BrookNY 11794-8093, USA
2To whom correspondence should be addressed at: Department of Urology, SUNY at Stony Brook, HSC level 9 room 040,Stony Brook NY 11794-8093, USA. E-mail: [email protected]
BACKGROUND: Scrotal hyperthermia has been identified as a risk factor for male infertility. Laptop computers(LC) have become part of a contemporary lifestyle and have gained popularity among the younger population ofreproductive age. LC are known to reach high internal operating temperatures. We evaluated the thermal effect ofLC on the scrotum. METHODS: Right and left scrotal temperature (ScT) was measured in 29 healthy volunteersin two separate 60 min sessions. ScT was recorded from thermocouples on a digital datalogger every 3 min with theworking LC in a laptop position and in the same sitting position with approximated thighs without LC. RESULTS:ScT increased significantly on the right and left side in the group with working LC (2.88C and 2.68C, respectively;P < 0001) and without LC (2.18C, P < 0.0001). However, ScT elevation with working LC was significantly higher(P < 0.0001). CONCLUSIONS: Working LC in a laptop position causes significant ScT elevation as a result of heatexposure and posture-related effects. Long-term exposure to LC-related repetitive transient scrotal hyperthermiais a modern lifestyle feature that may have a negative impact upon spermatogenesis, specifically in teenage boysand young men. Further studies of such thermal effects on male reproductive health are warranted.
shorts and suspensories, car drivers (Mills, 1919; MacLeod,
It has been estimated that 15 – 20% of couples attempting to
1951; Kapadia and Phadke, 1955; Robinson and Rock, 1967;
achieve pregnancy are unable to conceive. A male factor is
Brindley, 1982; Brown-Woodman et al., 1984; Nistal and
the main single diagnostic category in more than half of
Paniagua, 1984; Rubben et al., 1986; Figa-Talamanca et al.,
them (Gilbaugh and Lipshultz, 1994). Gradual decline in
1992; Saikhun et al., 1999; Bujan et al., 2000). Multiple
sperm production in men has become a growing concern and
human studies have confirmed deleterious effects of scrotal
subject of widespread debates in the last decades (Carlsen
hyperthermia on spermatogenesis (Rock and Robinson, 1965;
et al., 1992; Olsen et al., 1995; Fisch et al., 1996; Lerchl and
Robinson et al., 1968; Mieusset and Bujan, 1995; Kandeel
Nieschlag, 1996; Swan et al., 1997; Jegou et al., 1999). Sev-
eral factors have been implicated as possible causes of the
Local scrotal hyperthermia can be achieved by direct heat
deterioration of the male reproductive function, including
exposure or effect of body temperature and blunted physio-
endocrine disrupters, changes in lifestyle and exposure to
logical testicular cooling mechanism (Kapadia and Phadke,
heat (Figa-Talamanca et al., 1992; Mieusset and Bujan,
1955; Robinson and Rock, 1967; Brindley, 1982).These fac-
1995; Toppari et al., 1996; Thonneau et al., 1998; Bujan
tors have been experimentally studied by various methods
including local scrotal hot water bath, direct heating with a
Testicular function is temperature dependent and requires
150 Wt electric light bulb, sitting position with thighs
a temperature 2 – 48C below body temperature (Thonneau
approximated to the scrotum, and scrotal insulation (Rock
et al., 1998). Elevated testicular temperature is a well-
and Robinson, 1965; Robinson et al., 1968; Brindley, 1982).
documented mechanism of abnormal spermatogenesis in
Recently potential exposure of male reproductive function to
common diseases associated with male infertility, e.g. varico-
certain lifestyle factors (sedentary work position, prolonged
cele, undescended testis (Mieusset et al., 1985; Goldstein and
car driving, wearing plastic lined diapers by children) has
Eid, 1989; Lerchl et al., 1993; Wright et al., 1997).
been linked to increased scrotal temperature and delayed
Numerous factors can elevate scrotal temperature either by
conception (Bujan et al., 2000; Hjollund et al., 2000, 2002a;
whole body or local scrotal heating. Elevated scrotal
temperature was found in men with febrile illness, retractile
Continued improvements in power, size and price of LC
testes, occupations associated with high temperature expo-
have favored their increased use in a younger population of
sure, hot bath and sauna users, men wearing tight jockey
reproductive age. However, LC actively generate heat and can
Human Reproduction q European Society of Human Reproduction and Embryology 2004; all rights reserved
reach internal operating temperature . 708C. Frequently posi-
tioned close to the scrotum, this device is capable of produ-
Median body temperature for both sessions was 378C (range
cing direct local heat exposure. In addition, the use of a LC
36.78 – 37.018C). There was no significant difference in
requires a special body position in order to balance the com-
median baseline scrotal temperatures of the right and left
puter on a lap when the scrotum is trapped between closely
side between groups with LC and without LC (P ¼ 0.075
and P ¼ 0.083, respectively). As shown in Figure 1, median
With the exception of an anecdotal report of penile and
left scrotal temperature increased in men with working LC
scrotal burns after LC use (Ostenson, 2002), the effect of
and without LC. Median right scrotal temperature also
portable computers in a laptop position on scrotal tempera-
increased in both groups, although it remained constant in
ture is not known. We performed the first study to investigate
men without LC after 30 min (Figure 2). Scrotal temperature
scrotal temperature changes in LC users.
elevation on the right and left side in 60 min was significantin both groups (P , 0.0001). However, this temperature
elevation (60 min gradient) on the right and left side was sig-nificantly higher in the group with working LC compared to
Twenty-nine healthy male volunteers, 21 to 35 years old (median
the group without LC (P , 0.0001; Table I).
age 24) were recruited. All subjects completed the study. The study
The median external bottom surface temperature of the
was approved by the Institutional Review Board and conducted atthe General Clinical Research Center. All men signed an informed
two working LCs increased from 30.918C (29.11 – 32.568C)
consent form, completed a health questionnaire and underwent a
at the beginning of the experiment to 39.928C (39.50 –
physical exam. Exclusion criteria included history or presence of
40.288C) at 60 min. There were no significant differences in
varicocele, cryptorchidism, scrotal surgery, skin disease, infertility,
the initial (P ¼ 0.329) and final external bottom surface
testicular size discrepancy, recent febrile illness and prolonged or
temperature (P ¼ 0.999) between two LC brands based on
occupational exposure to heat (e.g. sauna or hot bath users, pro-
fessional drivers, workers exposed to high temperature). Two 1 hsessions of scrotal temperature measurements were performed ondifferent days in the same room with median room temperature of22.288C (range 21.89 – 22.618C). Men were dressed in the samecasual attire for each session. Sessions with and without LC wereconducted at the same time of the day between 8.00 and 16.00(median time 11.37).
Body temperature was taken orally prior to each session. Each
participant spent 15 min standing in the room to adjust to the roomtemperature before being seated in the chair. Two cutaneous ther-mocouples (5SRTC-TT J type Teflon insulated wire, Omega Engin-eering Inc., Stamford, CT; maximum service temperature of 2608C)were attached to the unshaved scrotal skin anteriorly correspondingto the right and left testis using thin transparent tape to cover thesensor end of the thermocouple. Nonworking LC was positioned onthe lap. After the participant adopted the position with approximatedthighs necessary to comfortably balance the LC on the lap, the LCwas removed. This position was maintained throughout the complete
Figure 1. Median left scrotal temperature (8C) in men with working
session. The thermocouples were connected to digital thermometer/
datalogger HH84 (Omega Engineering Inc., Stamford, CT). Separatemeasurements of scrotal temperature on the right and left side wererecorded in 3 min intervals. The datalogger was calibrated daily.
Two different brand name Pentium 4 LC were used randomly.
The LC was turned on for 15 min before being positioned on thelap. Thermocouples were attached the same way and at the sameplace on the right and left side of the scrotum. Then the LC wascomfortably positioned on the lap and the participant adopted andmaintained the same sitting posture as at the previous session with-out the LC. Temperature measurements were performed at 3 minintervals. Measurements of the external bottom surface temperatureof the working LC were taken randomly at the same time intervals.
Statistical analysis was carried out in SAS version 8.2 (SAS InstituteInc, Cary, NC). Data are summarized with medians and ranges (minand max) in centigrade units. Wilcoxon signed-ranks tests for tworelated samples were used to test for differences between scrotaltemperatures for each side separately with P , 0.05 considered
Figure 2. Median right scrotal temperature (8C) in men with work-
Increase in scrotal temperature in laptop computer users
Table I. Median scrotal temperature (8C) with working LC in a laptop position and without LC
inhibiting spermatogenesis (Wang et al., 1997; Partsch,
The negative effect of exogenous scrotal heat exposure on
2000). A strong negative association was found between high
spermatogenesis has been demonstrated by numerous exper-
scrotal temperature and sperm count as well as Inhibin B,
which is considered a biochemical marker of spermatogen-
hyperthermia has been linked to certain lifestyle factors
esis. Sperm concentration decreased by 40% per 18C incre-
including use of disposable plastic lined diapers in children,
ment of median daytime scrotal temperature (Hjollund et al.,
prolonged car driving and sedentary work (Bujan et al.,
2002b). In one animal study, an increase in scrotal tempera-
2000; Hjollund et al., 2000, 2002a; Partsch, 2000). Laptop
ture resulted in impaired fertility even without any detectable
computers have become an integral part of a modern life-
changes in semen analysis (Mieusset et al., 1992).
style. By 2005, LC use in USA will grow to 60 million units,
The frequency and time of heat exposure capable of produ-
while worldwide usage is predicted to be at 150 million
cing reversible or irreversible changes in human spermato-
units. Use of LC is growing among teenagers and young men
genesis are not known. Studies of frequency of heat exposure
and durability of inhibition of spermatogenesis revealed sig-
Heat remains one of the most critical and unresolved
nificant but reversible (within weeks or months) changes
issues in computer design. Frequent use of LC in a laptop
after single or multiple short-term scrotal heating (Robinson
position directly exposes the scrotum to the dissipated high
et al., 1968; Kandeel and Swerdloff, 1988) and total body
internal operating temperature of the machine.
heating (Procope, 1965; Brown-Woodman et al., 1984).
Maintenance of a proper testicular temperature is essential
However, LC may produce significant repetitive transient
for normal spermatogenesis. Our study demonstrates statisti-
scrotal hyperthermia for years. Insufficient recovery time
cally significant elevation of scrotal temperature in LC users.
between heat exposures may cause irreversible or partially
Since scrotal skin temperature strongly correlates with testi-
reversible changes in male reproductive function. In one
cular temperature, such elevation corresponds to a testicular
study, men exposed to high temperature for 5 – 7 years were
hyperthermia (Kitayama, 1965; Kurz and Goldstein, 1986;
found to have oligoasthenoteratozoospermia, while those
Hjollund et al., 2002a). Portable computers in a laptop pos-
exposed for 12 – 15 years had azoospermia (Dada et al.,
ition produce scrotal hyperthermia by both the direct heating
2003). Another study of 449 male partners of infertile
effect of the computer and the sitting position necessary to
couples revealed that patients with ‘idiopathic’ oligoastheno-
balance computer on the lap with the scrotum trapped tightly
teratozoospermia are more exposed to genital heat stress than
between the thighs. Increased scrotal temperature in a sitting
normozoospermic men (Jung et al., 2002).
position with thighs together has been reported in previous
Our study demonstrates that working with a LC produces
studies (Rock and Robinson, 1965; Brindley, 1982; Bujan
significant elevation of scrotal temperature. While scientific
et al., 2000). However, the thermal impact of working LC in
background suggests a negative impact of scrotal hyperther-
a laptop position is significantly higher than positional scrotal
mia upon spermatogenesis, further studies of this particular
type of thermal exposure with LC are warranted. Meanwhile,
In our study, median left and right side scrotal temperature
limited use of LC in a laptop position by teenage boys and
increase in the group with working LC was 2.68C and 2.88C,
young men in reproductive age may be considered, to avoid
respectively. The magnitude of scrotal hyperthermia associ-
ated with abnormal spermatogenesis is unclear. While anincrease in scrotal temperature of 18C was sufficient to sup-press spermatogenesis in some studies, others did not confirm
those findings when scrotal temperature rose by 0.8 – 18C
This project has been supported by the Department of Urology,
(Rock and Robinson, 1965; Wang et al., 1997). Higher testi-
Stony Brook University Hospital and General Clinical research
cular or scrotal temperature elevation between 1 and 2.98C
was more consistently associated with a sustained and con-siderable negative effect on spermatogenesis and fertility
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Submitted on May 4, 2004; resubmitted on September 27, 2004; accepted on
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A 59-year-old woman was admitted for rapid health degradation, with abdominal pain, icterus and ascites. She was known for a two years long-standing breast cancer aggra-vated progressively by multi-organ metastases. The patient was treated by hormonal therapy (Tamoxifen followed by Exemestane) and chemotherapy (5-Fluorouracil – Epirubucin – Cyclophosphamide then Cisplatine – 5-Fluo