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Sex differences in psychophysical and neurophysiological responses to pain in older adults: a cross-sectional study

View Article: PubMed Central

ABSTRACT

Background: Neuroimaging studies in younger adults have demonstrated sex differences in brain processing of painful experimental stimuli. Such differences may contribute to findings that women suffer disproportionately from pain. It is not known whether sex-related differences in pain processing extend to older adults.

Methods: This cross-sectional study investigated sex differences in pain reports and brain response to pain in 12 cognitively healthy older female adults and 12 cognitively healthy age-matched older male adults (age range 65–81, median = 67). Participants underwent psychophysical assessments of thermal pain responses, functional MRI, and psychosocial assessment.

Results: When compared to older males, older females reported experiencing mild and moderate pain at lower stimulus intensities (i.e., exhibited greater pain sensitivity; Cohen’s d = 0.92 and 0.99, respectively, p < 0.01) yet did not report greater pain-associated unpleasantness. Imaging results indicated that, despite the lower stimulus intensities required to elicit mild pain detection in females, they exhibited less deactivations than males in regions associated with the default mode network (DMN) and in regions associated with pain affect (bilateral dorsolateral prefrontal cortex, somatomotor area, rostral anterior cingulate cortex (rACC), and dorsal ACC). Conversely, at moderate pain detection levels, males exhibited greater activation than females in several ipsilateral regions typically associated with pain sensation (e.g., primary (SI) and secondary somatosensory cortices (SII) and posterior insula). Sex differences were found in the association of brain activation in the left rACC with pain unpleasantness. In the combined sample of males and females, brain activation in the right secondary somatosensory cortex was associated with pain unpleasantness.

Conclusions: Cognitively healthy older adults in the sixth and seventh decades of life exhibit similar sex differences in pain sensitivity compared to those reported in younger individuals. However, older females did not find pain to be more unpleasant. Notably, increased sensitivity to mild pain in older females was reflected via less brain deactivation in regions associated with both the DMN and in pain affect. Current findings elevate the rACC as a key region associated with sex differences in reports of pain unpleasantness and brain deactivation in older adults. Also, pain affect may be encoded in SII in both older males and females.

Electronic supplementary material: The online version of this article (doi:10.1186/s13293-015-0041-y) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

Rostral anterior cingulate cortex. Sex differences in the association between unpleasantness reported and percent signal change values in the rostral anterior cingulate cortex (rACC) for the condition of mild pain > warmth
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Fig8: Rostral anterior cingulate cortex. Sex differences in the association between unpleasantness reported and percent signal change values in the rostral anterior cingulate cortex (rACC) for the condition of mild pain > warmth

Mentions: To explore and describe the perceptual importance of significant sex differences in brain activations, we examined the associations of the BOLD signal change values in each of the ROIs above showing significant sex differences with psychophysical self-reports. Summaries of these associations for all 24 participants and for each sex (n = 12 in each group) are described in Table 7. Signal change values for each ROI are presented in Figs. 8 and 9.Fig. 8


Sex differences in psychophysical and neurophysiological responses to pain in older adults: a cross-sectional study
Rostral anterior cingulate cortex. Sex differences in the association between unpleasantness reported and percent signal change values in the rostral anterior cingulate cortex (rACC) for the condition of mild pain > warmth
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4647695&req=5

Fig8: Rostral anterior cingulate cortex. Sex differences in the association between unpleasantness reported and percent signal change values in the rostral anterior cingulate cortex (rACC) for the condition of mild pain > warmth
Mentions: To explore and describe the perceptual importance of significant sex differences in brain activations, we examined the associations of the BOLD signal change values in each of the ROIs above showing significant sex differences with psychophysical self-reports. Summaries of these associations for all 24 participants and for each sex (n = 12 in each group) are described in Table 7. Signal change values for each ROI are presented in Figs. 8 and 9.Fig. 8

View Article: PubMed Central

ABSTRACT

Background: Neuroimaging studies in younger adults have demonstrated sex differences in brain processing of painful experimental stimuli. Such differences may contribute to findings that women suffer disproportionately from pain. It is not known whether sex-related differences in pain processing extend to older adults.

Methods: This cross-sectional study investigated sex differences in pain reports and brain response to pain in 12 cognitively healthy older female adults and 12 cognitively healthy age-matched older male adults (age range 65–81, median = 67). Participants underwent psychophysical assessments of thermal pain responses, functional MRI, and psychosocial assessment.

Results: When compared to older males, older females reported experiencing mild and moderate pain at lower stimulus intensities (i.e., exhibited greater pain sensitivity; Cohen’s d = 0.92 and 0.99, respectively, p < 0.01) yet did not report greater pain-associated unpleasantness. Imaging results indicated that, despite the lower stimulus intensities required to elicit mild pain detection in females, they exhibited less deactivations than males in regions associated with the default mode network (DMN) and in regions associated with pain affect (bilateral dorsolateral prefrontal cortex, somatomotor area, rostral anterior cingulate cortex (rACC), and dorsal ACC). Conversely, at moderate pain detection levels, males exhibited greater activation than females in several ipsilateral regions typically associated with pain sensation (e.g., primary (SI) and secondary somatosensory cortices (SII) and posterior insula). Sex differences were found in the association of brain activation in the left rACC with pain unpleasantness. In the combined sample of males and females, brain activation in the right secondary somatosensory cortex was associated with pain unpleasantness.

Conclusions: Cognitively healthy older adults in the sixth and seventh decades of life exhibit similar sex differences in pain sensitivity compared to those reported in younger individuals. However, older females did not find pain to be more unpleasant. Notably, increased sensitivity to mild pain in older females was reflected via less brain deactivation in regions associated with both the DMN and in pain affect. Current findings elevate the rACC as a key region associated with sex differences in reports of pain unpleasantness and brain deactivation in older adults. Also, pain affect may be encoded in SII in both older males and females.

Electronic supplementary material: The online version of this article (doi:10.1186/s13293-015-0041-y) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus