The purpose of this study was to explore the relationship between breast size, thoracic kyphosis, bra fit and thoracic pain in post-menopausal women. Menopause and ageing are similar but distinct variables. Menopause exists as period of rapid transition for women in terms of lean tissue mass [27], bone mineral density [28], fat tissue distribution [27], and a range of subsequent anthropometrical dimensions. Identifying if and how these changes might impact on pain experienced by post-menopausal women will help direct future clinical practice.
The sample of women who participated in this study were relatively healthy, community dwelling individuals who were not self-selected on the basis of seeking treatment for pain.
The majority of women were overweight (BMI > 25-30) or obese (BMI > 30), which is coherent with national statistics showing this to be the largest and most rapidly expanding category in women, particularly post-menopausally [29]. Body weight and BMI were significantly associated with breast size, indicating somewhat intuitively that larger women have larger breasts. Women with a greater BMI and larger breasts were more likely to have their bra fitted but the majority of women in this study were not wearing the correct bra size.
Wearing incorrectly sized bras has also been reported in young women with thoracic pain [16]. The procedure for fitting a bra is reasonably universal but due to the constraints on how it can be measured, some random error cannot be excluded in the process. Assumed differences between bra brands together with other substantiated variables such as measurement methodology and chest expansion during measuring [30] are factors affecting the inter-rater reliability in bra measurements.
Breast hypertrophy has been associated with menopause with many women reporting an increase in breast size post-menopause [8]. Women of post-menopausal age are more likely to seek reduction mammoplasty surgery [11, 13], suggesting that the postmenopausal increase in breast size is pertinent to symptoms leading women to seek such surgery. There was large variation in the bra size of participants in this study, varying as it did from 10A to 22E with an average size of 16C. Whilst there is no consensus on the definition of macromastia, women with bra cup sizes exceeding DD appear most frequently in reduction mammoplasty studies [11]. If bra cup size is taken as an indicator of breast size, it might be assumed that the DD cup size is a threshold at, or above which, common symptoms associated with macromastia develop. This might be usefully regarded by clinicians treating this category of women but further clarification is needed as to whether breast size, mass, shape and position are influential in part or combination to this relationship.
Large breast size has been purported to exist as a significant health burden in some postmenopausal women, operating mainly through the mechanism of pain [13]. The two procedures used for the assessment of pain in this study provided both localised and global subjective indications of thoracic tenderness and pain respectively. A significant moderate relationship was found between breast size and global thoracic pain. Localised tenderness on palpation at the thoracic levels T7 and T8 was significantly associated with breast size. Although a series of t-tests was used to examine these relationships and no corrections for multiple comparisons were implemented, the p-value for T7 was very small (p < 0.007) and the finding of significant associations at two adjacent levels add plausibility to the finding.
Whilst a causal relationship between breast size and thoracic pain (particularly at T7 and T8) cannot be concluded from these cross-sectional data, it is encouraging to find that existing literature has highlighted potential mechanisms that are consistent with the findings of this study. The pulley-like action of brassiere straps and associated downward drag of breast weight has been implicated in the cause of pain in the scapular elevator muscles [15]. It might be speculated that scapular retractor muscles (regional to T7/8) are also a potential source of pain as the shoulder girdle protracts with a larger anterior load (larger breasts). These findings and those produced in the present study provide anatomical, clinical and statistical confirmation and consensus of the plausibility of such a mechanism and highlight the mid thoracic region as one which is implicated with increased stress afforded by larger breasts. Further investigation into the shape and volume of breast tissue in post-menopausal women would help clarify the specific biomechanical impact of breast size relative to overall upper body size/fat distribution which could be used to further elucidate possible pain mechanisms.
Collectively the results of this study support the general consensus of reduction mammoplasty research indicating that breast size is indeed instrumental in producing symptoms of upper back pain in post-menopausal women. With the majority of women undergoing breast reduction surgery being overweight or obese [13] and knowing that pain prevalence has been linked to obesity [31] with the relative odds of chronic pain increasing with every unit of BMI [32], it is helpful that the present study has identified an association between breast size and pain which appears independent of body weight and BMI. If breast size had not been shown to be the most important independent predictor of thoracic pain in this study then it might be speculated that the improvements in symptoms seen in reduction mammoplasty studies are less contingent on actual breast size but more so on breast weight, particularly since some studies report the removal of up to 2330 g per breast [12]. This could arguably translate into a somewhat significant immediate reduction in body weight (and BMI) post-surgery and thus explain the symptom improvement based on the aforementioned relationships.
The results of this study indicate that upper thoracic pain exists in women of postmenopausal age with 82% of participants indicating some pain in the upper back (SF-MPQ score >0). Progressive change in adult spinal sagittal posture is a characteristic feature of the ageing process which is accentuated in women, around the menopause through osteoporosis [6]. Conversely, It is now well-established that the sagittal curvatures of the spine are geometric parameters that are known to have a significant influence on mechanical properties during compression loading [33, 34]. Sagittal posture imbalance has been shown to elevate loads and intervertebral disc stresses, thus posing as a plausible mechanism for pain in persons with an increased thoracic kyphosis [6]. Whilst the results of this study cannot confirm the association between increasing kyphosis and global or localised thoracic pain in post-menopausal women, it does highlight the existence of thoracic pain in this population. Breast size is associated with this pain at thoracic levels T7 and T8, which are levels that have been previously identified in postmenopausal women as being frequently deformed (due to wedging or fracture) [4, 6] and close to the apex of kyphosis (T6) [5]. Given the abundance of existing literature that has identified relationships between increasing age [6], BMI [7] and pain [35] with accentuated thoracic kyphosis, further examination of these variables in post-menopausal women is suggested.
In summary, the findings of this study show a correlation between breast size and upper back pain in postmenopausal women. This is unrelated to thoracic kyphosis and appears independent of co-existing associations between increasing BMI and thoracic pain. Whilst women with larger breasts are more likely to have their bra fitted, this appears unrelated to thoracic pain.
This study has identified a handful of correlates associated with thoracic pain in post-menopausal women. It is acknowledged that additional possible correlates exist and in this study it was not possible to account for all of these. Bone mineral density, physical activity levels, emotion and in some instances, occupational stresses, are factors that were not measured and may have confounded our results. Random error associated with breast size and thoracic kyphosis measurement should be considered as limitations of this study. In addition, the results of this study were reliant on the accuracy of responses to self-reported measures of pain, bra wear and fitting. Collectively the under or over-reporting of details pertaining to these measures cannot be discounted and should also be considered limitations of this study.
Further research is required to examine women postmenopausally. It exists as a transitional time for women in terms of breast size and BMI, which could also reflect a transitional time in terms of pain. An intuitive and proven relationship exists between breast size and body weight and this is related to thoracic pain. Elucidating possible mechanisms to explain these relationships would be a logical progression to understanding why they exist and how clinical practice might be improved in the treatment of post-menopausal women presenting with thoracic pain.