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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 (Robinson et al., 1968; Zorgniotti and MacLeod, 1973; Brindley GS (1982) Deep scrotal temperature and the effect of clothing, air Mieusset et al., 1985; Shafik, 1991). Therefore, a scrotal tem- temperature, activity, posture and paraplegia. Br J Urol 54,49– 55.
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