Are there gender differences in pain perception?
Pain (Care and treatment)
Soetanto, Angie L.F.
Chung, Joanne W.Y.
Wong, Thomas K.S.
|Publication:||Name: Journal of Neuroscience Nursing Publisher: American Association of Neuroscience Nurses Audience: Professional Format: Magazine/Journal Subject: Health care industry Copyright: COPYRIGHT 2006 American Association of Neuroscience Nurses ISSN: 0888-0395|
|Issue:||Date: June, 2006 Source Volume: 38 Source Issue: 3|
|Topic:||Event Code: 310 Science & research; 200 Management dynamics|
Abstract: Chronic pain conditions are increasingly prevalent.
However, very little is known about the relationship between pain and
gender. The purposes of this study were to determine gender differences
in pain threshold and tolerance among Chinese adults in Hong Kong and to
examine the role of anxiety in pain perception. One hundred
seventy-eight healthy, pain-free adults (89 men and 89 women) were
recruited from a local university by convenience sampling to participate
in the study. All participants completed the State and Trait Anxiety
Inventory and underwent a laboratory pain task to determine their pain
threshold and tolerance levels. Pain was assessed by using the Pain
Intensity Verbal Rating Scale-Chinese version. Compared to men, women
had a lower threshold (p < .001) and tolerance (p < .001) for
pressure pain, and women reported more pain (p < .01) at the pain
tolerance level. Higher trait anxiety scores were associated with higher
pain report in men only (r  = .22, p = .04). The study indicated
that gender differences in pain perception exist among the Chinese
population in Hong Kong. A better understanding of the factors that
contribute to gender differences in pain perception could reduce gender
bias in pain management.
It is important to investigate gender differences in pain perception because many painful diseases such as rheumatoid arthritis, migraine headache, and low back pain are more prevalent among women than among men (Berkley, 1997; LeResche, 2000). Women not only report more pain in their lifetime, they also experience more intense pain in more parts of their body than men (Riley) Robinson, Wise, Myers, & Fillingim, 1998; Unruh, 1996). In Hong Kong, there is increasing evidence to suggest that many chronic pain conditions, such as osteoporosis and musculoskeletal disease, are more prevalent among women (Ho et al., 1999; Miu, Chan, & Chan, 2004) and that women are at greater risk of experiencing chronic pain than men (Ng, Tsui, & Chang, 2002). Very little is known about the relationship between pain and gender in this culture, and the reasons for gender differences in pain perception are not clear. Physiological as well as psychosocial factors are thought to contribute to gender differences in pain perception. For example, increased cardiovascular reactivity has been reported to reduce pain sensitivity in men (Lash, Steven, & Eisler, 1995), and the interaction of gonadal hormones with pain mechanisms has been found to increase pain sensitivity in women (Berkley, 1997; Riley, Robinson, Wise, & Price, 1999). Psychosocial factors such as gender-role expectation have been reported to affect men's and women's perceptions of pain differently (Levine & De Simone, 1991; Wise, Price, Myers, Heft, & Robinson, 2002).
Evidence increasingly suggests that anxiety, in addition to physiological and psychosocial factors, may interact with gender to affect the overall perception of pain. For example, Keogh and Birkby (1999) examined the influence of gender and anxiety sensitivity on the perception of cold pressor pain. High anxiety sensitivity was associated with enhanced pain reported in women but not in men. More recently, Jones, Zachariae, and Arendt-Nielsen (2003), using the State-Trait Anxiety Inventory (STAI), found that male participants who scored above the median on anxiety reported significantly greater pain intensity and unpleasantness compared with men who scored below the median. This effect was not found in women, regardless of whether they scored above or below the median. Because anxiety may have a differential effect on the pain responses of men and women, it is important that the relationship among pain, gender, and anxiety be clarified.
This study investigated gender differences in pain perception among healthy, pain-free Hong Kong Chinese adults, using experimental pressure pain. According to Fillingim and Maixner (1995), gender-associated differences in pain sensitivity occur most consistently using experimental methods that produce pressure pain, because these sensations mimic pain experienced in the natural environment. We hypothesized that female participants would have a lower threshold and tolerance for pressure pain and that anxiety would affect pain report in male and female participants differently.
One hundred seventy-eight adults (89 men and 89 women) recruited by convenience sampling from a local university were invited to participate in the study. Participants were screened for psychological and medical symptoms using a health history questionnaire. Exclusion criteria included feelings of pain immediately before the experiment, chronic pain, and the use of over-the-counter medication within the past 6 hours. The experimental procedure was approved by the Human Subject Ethics Committee of Hong Kong Polytechnic University.
Upon arrival, all participants read and signed a consent form acknowledging that they were to participate in a pressure pain task to determine their pain threshold and pain tolerance. They also understood that they could withdraw, without prejudice, from the experiment at any time. Next, participants were asked to complete the State-Trait Anxiety Inventory-Form Y (STAI-Y; Spielberger, 1983), in its adapted Chinese version by Paul Yung and Bernard Lau. To reduce error, all procedures were administered by the same researcher in a consistent manner. The following standardized instructions were given to all participants before the pain task:
Pressure Pain Threshold and Tolerance Measures
Pressure pain threshold (PPTh) and pressure pain tolerance (PPTo) were determined on the middle joint of the middle finger of the participant's nondominant hand. Pressure stimuli were delivered via the Precision Pain Source instrument (PPS-3, manufactured by Cygnus, Inc., Paterson, NJ), which is software controlled. To determine PPTh, participants were instructed to say Painful when the pressure stimuli first became painful. To determine tolerance, participants were instructed to say Stop when they no longer felt able to tolerate the pain. The amount of pressure applied at both threshold and tolerance was recorded. The maximum pressure was set at 1,000 g. If a participant failed to report pain after reaching the maximum value, an alarm would sound and pain induction would terminate immediately.
Pain Intensity Ratings
Participants were asked to rate perceived pain intensity using a locally developed pain rating scale called the Pain Intensity Verbal Rating Scale-Chinese Version (PWRS-CV; Chung, Wong, Yang, & Wong, 1999). This scale has 10 descriptors: 0 = no pain, 1 = slight pain, 2 = quite painful, 3 = bearable pain, 4 = painful, 5 = very painful, 6 = indescribable pain, 7 = unbearable pain, 8 = excruciating pain, 9 = crushing the heart and lungs, and 10 = crucifying pain. The PIVRS-CV has been reported to be a culturally valid and reliable tool for assessing pain in the Hong Kong Chinese population (see Chung et al.  on cultural validity and Lui, Chung, & Wong  on reliability).
State and Trait Anxiety
The adapted Chinese version of the STAI-Y was thought to be most appropriate for assessing state and trait anxiety in this study. The STAI-Y is a self-report questionnaire that contains 20 items for measuring state anxiety and 20 items for measuring trait anxiety. State anxiety can be grouped as low (20-39), moderate (40-59), and high (60-80). A mean trait anxiety score exceeding 32.7 is considered as high trait anxious; a mean score below 32.7 is considered low trait anxious (Spielberger, 1983). The adapted Chinese version of the STAI-Y has been tested for validity and reliability. The results showed that the instrument is a culturally relevant (CVI = 0.9) and reliable (alpha = 0.88 [state]; 0.92 [trait]) tool for assessing state and trait anxiety among the Chinese population in Hong Kong (Soetanto, Chung, & Wong, 2004).
Chi-square analyses were performed on several variables. Results indicated that the male and female groups did not differ significantly in age, employment status, marital status, or religion (minimum [chi square] [2, N = 178] = 1.06; p = .06). A summary of the demographic data is presented in Table 1.
Gender Differences in Pain Threshold and Tolerance
Gender differences in pain threshold and pain tolerance were compared using independent t tests. Two female participants did not complete the pain tolerance tasks; their data were not included in the analysis. Results showed significant gender differences in pain threshold between men (M = 453.69 g, SD = 145.75) and women (M = 382.57 g, SD = 112.68), t(175) = 3.63, p = .001. Significant gender differences in pain tolerance between men (M = 968.64 g, SD = 153.15) and women (M = 732.57 g, SD = 218.91), t(174) = 8.27, p = .001 were also found.
The effect sizes for pain threshold and pain tolerance were calculated using the following formula: Cohen's d = M 1 - M 2 / pooled standard deviation. For pain threshold, Cohen's d = mean male threshold--mean female threshold / pooled standard deviation. Therefore, Cohen's d = 453.70 - 382.3 / 134.80 = 0.528. Similarly, for pain tolerance, Cohen's d = mean male tolerance--mean female tolerance / pooled standard deviation. Therefore, Cohen's d = 968.64 - 732.57 / 186.03 = 1.27. These results suggest that there was a medium effect size for pain threshold and a large effect size for pain tolerance.
Gender Differences in Pain Report
Gender differences in pain report were compared using independent t tests. The results showed no significant gender difference in pain report at the pain threshold level, but at the pain tolerance level, female participants rated pain as more intense (M = 5.40, SD = 1.80) compared with male participants (M -- 4.72, SD = 1.67), t(174) = 2.62, p = .01.
Gender Differences in State and Trait Anxiety
Gender differences in state and trait anxiety were assessed using independent t tests. The results showed no significant gender differences in either state or trait anxiety scores as measured by the adapted Chinese version of the STAI-Y. The mean state scores for males as measured by the STAI Y-1 (M = 39.67; SD = 9.24) and for females (M = 38.21; SD = 8.54) did not differ significantly. The mean trait score for males as measured by the STAI Y-2 (M = 42.66; SD = 8.13) and for females (M = 42.07; SD = 7.28) also did not differ significantly.
Correlational analyses were performed separately on the male and female subgroups to determine the relationship among pain, gender, and anxiety (Table 2).
The results showed that high trait scores were associated with higher pain report in men only (r  = .22; p < .05). These results suggested that more trait anxious men reported more pain. There was also a strong positive correlation between STAI Y-1 and STAI Y-2 scores for both men (r  = .81; p < .01) and women (r  = .67; p < .01), suggesting that participants with high state scores also have high trait scores.
This study confirms that there are gender differences in pain perception among Chinese adults in Hong Kong.
Consistent with previous studies (Wise et al., 2002; Riley et al., 1998), women were found to display a lower threshold and a lower tolerance for pressure pain compared with men. One possible explanation could be that women are more aware of pain sensations. According to Fillingim and Maixner (1995), women experience more pain throughout their lifetime due to biological events such as menstruation and childbirth, and, as a result, women may develop a greater awareness of pain over time.
It is likely that male participants tolerate more pain because of psychosocial factors such as gender-role expectations. In Hong Kong, traditional gender-role assumptions are endorsed and men are expected to be strong (Yip, 2003). It is likely that male participants chose to tolerate more pain to impress the female researcher. The display of "macho" behavior in experimental pain studies is not uncommon. The large effect size for pain tolerance between men and women is consistent with observations that men generally display a higher tolerance for pain in experimental settings (Riley et al., 1998).
The findings support the view that women generally report higher pain levels than men (Riley et al., 1998). One reason women report more intense pain may be early childhood socialization; girls are allowed to express pain behavior more openly, but boys are expected to be stoic (Fearon, McGrath, & Achat, 1994). It is also possible that women in this study reported more pain because they felt more pain. Several studies have suggested that increased cardiovascular reactivity may reduce pain sensitivity in men (Lash et al., 1995) and that the interaction of gonadal hormones with pain mechanisms may lead to increased pain sensitivity in women (Berkley, 1997; Riley et al., 1999). Hence, both socialization and biological factors may contribute to the higher pain report of female participants in this study.
We did not find any significant gender difference in self-reported state and trait anxiety, possibly because the male and female groups were very similar in demographic characteristics (see Table 1). However, male participants who gave higher ratings for trait anxiety reported significantly greater pain intensity compared with male participants who gave lower ratings for trait anxiety. No such effect of anxiety on pain report was observed for female participants. This observation is consistent with the findings of Jones et al. (2003). They found that women in the high-anxiety subgroup experienced a higher state of arousal during painful stimulation; this arousal might have reduced pain sensitivity, as anxiety competes with nociception for attention. This finding may explain why several Hong Kong studies found men report more pain and consume more patient-controlled analgesia than women (e.g., Lam, Lauder, Lain, & Gandek, 1999; Tsui et al., 1996). Because anxiety plays a major role in pain perception, more research is needed to understand the modulatory effects of anxiety on the experience of pain between the sexes.
The findings of this study imply that gender should be taken seriously in pain management. According to Lau (2000), women in Hong Kong live longer than men; 50% of postmenopausal women in Hong Kong are likely to suffer from chronic pain conditions. This is an alarming statistic. Greater awareness of the relationship between pain and gender will ensure that women are not at a disadvantage in pain management. The likelihood that high trait anxiety may affect the sensory aspect of pain perception in men also warrants further investigation. Since the Asian economic crisis of 1997, the incidence of anxiety disorders and depression has increased, especially among Hong Kong men (Wong, 2000). This increase in anxiety may affect pain perception. Further investigation into the relationship between anxiety and pain perception in men is needed to ensure that men are not also at a disadvantage in pain management.
The results of this study are limited by the fact that one female researcher conducted the study. In an earlier study (Levine & De Simone, 1991), the gender of the researcher was found to affect pain perception by male participants, although the effect is not consistent (Feine, Bushnell, Miron, & Duncan, 1991). Future studies should include both male and female researchers to balance any effects of researcher gender on pain report.
Gender differences in pain perception exist across cultures. The current findings add to the growing literature on gender differences in pain perception and constitute a first important step toward understanding pain and gender among Chinese adults in Hong Kong. Future studies may extend this study to different ethnic groups in mainland China.
The authors are grateful to Paul Yung, PhD, for his permission to use the adapted Chinese version of the STAI-Y in this study. This study was supported by a research grant (G-V773) from Hong Kong Polytechnic University.
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Questions or comments about this article may be directed to Angie L. F. Soetanto, PhD RN, at email@example.com or 852/26098172. She is an assistant professor at Nethersole School of Nursing, Chinese University of Hong Kong, in Sha Tm, N.T., Hong Kong.
Joanne W. Y. Chung, PhD RN, is professor and associate head of the School of Nursing, Hong Kong Polytechnic University, Kowloon, Hong Kong.
Thomas K. S. Wong, PhD RN, is dean of the Faculty of Health and Social Science and chair of the School of Nursing, Hong Kong Polytechnic University, Kowloon, Hong Kong.
In this study, I wish to examine how sensitive you are to pressure pain and how much pressure you are able tolerate before you terminate the experiment. To do this, I need to apply increasing pressure using a penlike probe to the middle finger of your less dominant hand. For the first task, I would like you to say Painful when you just begin to feel uncomfortable. I will then remove the probe from your finger and ask you to rate the pain intensity on a 10-point pain-rating scale. For the second task, I will apply pressure again to the same finger, but this time I would like you to tolerate as much pain as you can and just say Stop when you cannot tolerate the pain anymore. Likewise, I will remove the probe from your finger and ask you to rate the pain intensity on the same 10-point scale.
Table 1. Demographic Characteristics of Participants (N=178) Male Female Variable (n = 89) (n = 89) n % n % Age (years) 18-30 56 31.5 66 37.1 31-45 29 16.3 23 12.9 46-60 4 2.2 0 0 Employment status Full-time student 48 27.0 54 30.3 Part-time student 13 7.3 9 5.0 Full-time employee 26 14.6 24 13.5 Part-time employee 2 1.1 2 1.1 Marital status Never married 63 35.4 71 39.9 Married 25 14.0 18 10.1 Divorced 1 0.6 0 0 Religious affiliation Buddhist 4 2.2 2 1.1 Roman Catholic 7 3.9 6 3.4 Non-Roman Catholic Christian 24 13.5 28 15.7 None 48 26.9 47 26.4 Other 6 3.4 6 3.4 Table 2. Correlations Between STAI Y-1 Scores, STAI Y-2 Scores, and Pain Report Variable Male (n = 89) Female (n = 87) STAI Y-1 Pain threshold -.034 -.201 Pain tolerance .145 -.100 STAI Y-2 .812 .669 STAI Y-2 Pain threshold -.001 -.128 Pain tolerance .217 * -.103 * p < .05 (two-tailed).
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