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Decline in Pulmonary Function Tests after Menopause

Objectives Menopause is the permanent cessation of menstruation resulting from the loss of ovarian follicular activity. There is limited and conflicting evidence for an association between lung function and menopause. The purpose of this study is to evaluate Pulmonary Function Test (PFT) in postmenopausal women. Methods Digital Spirometer was used to measure PFTs in premenopausal (n = 49) and postmenopausal (n = 46) women. Results Significant decline in many PFT parameters was observed. Conclusions Menopausal status is associated with low lung function.


Introduction
Menopause ( "end of monthly cycles" ) is a major but normal biological event in a woman' s life. All sex steroid hormone receptors are expressed in lung tissue. It is associated with marked reduction in levels of estradiol and has important effects on female physiology. Menopause has been associated with increased respiratory disorders. 1 Pulmonary Function Tests (PFTs) provide objective, quantifiable data of pulmonary function and spirometry tests based on voluntary forced expiration can detect changes in respiratory system.
Literature on lung health in women is confusing and effects of hormonal status on the airways often appear to be heterogenous. 2 Aim of the present study was to evaluate the effect of menopause on PFTs.

Results
Mean age of the women in postmenopausal group was 51 ± 2.49 years; mean body weight and BSA were higher in these subjects (Table 1). Mean height was comparable in the two groups.
Comparison of PFT parameters and flow rates between two groups showed reduced values in Group II subjects ( Difference between the two groups was not significant for FEV 3 and FEV 3 /FVC. All flow rate parameters viz. PEFR, FEF 25-75% , FEF 25% , FEF 50% , FEF 75% and MVV (L/min) were observed to be reduced in postmenopausal women ( Table 3).
Percentage of predicted values of all observed Spirometric parameters in the two groups were compared to exclude the effects of age and body mass index (BMI) on PFTs and were found to be in line with the other findings of our study except for FEF 75% (Fig. 1).  Postmenopausal women not only experience physical effects of aging but physiological aspects like lung function are also impacted, the cause being lack of ovarian hormones.
There is very less literature regarding effect of menopause on lung functions, even worldwide. We sought to investigate whether the menopausal status is related to the lung health.  16 and Triebner et al. 17 .
Impaired lung function, as measured by FVC or FEV 1 has been indicated as a marker of premature death Young et al. 18 .
But according to Songur et al. 19 and Jung et al. 20 , postmenopausal status is not significantly associated with lower   FVC. This deviation from our finding may be attributed to difference in ethnicity, environmental and geographical conditions and number of subjects investigated.   Generally expressed as a percentage, in normal adults, this ratio ranges from 75% to 85%. 13 FEV 1 /FVC ratio is a much more useful index than FVC alone and allows separation of patients with ventilator abnormalities into obstructive or restrictive type.
In the present study, mean value of FEV 1 /FVC of postmenopausal women was significantly less as compared to those of premenopausal women (45.79% vs. 70.10%, P < 0.0001) indicating obstructive pattern. Also, FEV 1 /FVC as percentage of predicted value in premenopausal women was significantly better as compared to that of postmenopausal women (93.24% vs. 62.15%, P < 0.0001).
Polly et al. 15 found the mean FEV 1 /FVC value to be higher but statistically non-significant in postmenopausal women. Strinic 14 found no decrease in FEV 1 /FVC in postmenopausal women. Difference between the two studies in terms of ethnicity, anthropometry, environmental and geographical conditions of subjects taken may have caused our study results to be different.

FEV 3 /FVC
Subjects with reduced FEV 3 /FVC have a progressively increased risk of developing obstruction. 23 In the present study, the observed mean values of FEV 3 / FVC of postmenopausal women were comparable with those of premenopausal women (P = 0.619).
Regarding the effect of menopause on this parameter, no report could be found in the literature.

PEFR
PEFR is a method of assessing the ventilatory capacity with single breath. It is largely a function of the caliber of large airways. It is abnormally decreased only in moderate to severe airway obstruction. 24 Important advantage of peak flow rate lies in the fact that it is relatively easily understood by the subject and physiologically a well-defined index.
In the present study, the observed mean value of PEFR was significantly less in postmenopausal women as compared to premenopausal women (P < 0.0001). 11. FEF 25-75% FEF 25-75% reflects effort independent expiration and the status of small airways.
In the present study, the mean values of FEF 25-75% of postmenopausal women were significantly less as compared to those of premenopausal women (P < 0.0001).
The results of our study are consistent with those of Polly et al. 15 and Hayatbakhsh et al. 16 .
No report could be found in the literature regarding effect of menopause on this parameter.

FEF 50%
In the present study, mean values of FEF 50% of postmenopausal women were significantly less as compared to those of premenopausal women (P < 0.0001). The results of our study agree with Strinic. 14

FEF 75%
In our study, mean values of FEF 75% in postmenopausal women were significantly less than in premenopausal counterparts (0.72 vs. 1.01 L/sec; P < 0.0008). However for this one parameter, when the observed values were compared to predicted values for two groups, the difference between them was not significant (101.24 vs. 95.30%; P = 0.516).
This can be attributed to factors like age and body size/BMI of our subjects because other factors which could vary the predicted values e.g. gender, race and altitude are same in two groups.
Our results agree with Strinic 13 .

MVV
MVV is the largest volume of air that can be moved into and out of the lungs in one minute by voluntary effort. It is a dynamic test of lung function and is considered to be a good guideline of the mechanical efficiency of lungs. However, MVV is less sensitive than FEF 25-75% .
In our study, mean MVV in postmenopausal women was significantly less as compared to premenopausal women (P < 0.0001).
Review of literature revealed no work in context of this parameter.

FVC time
Some obstructed patients have a relatively normal FVC in relation to their predicted values. However, the time required to expire their FVC is usually prolonged. 27 In the present study, the FVC time (min) taken by postmenopausal women was significantly more as compared to that premenopausal women (P = 0.006).
A search of available literature failed to show any report on this parameter.
Primary purpose of PFT is to identify the severity of pulmonary impairment. Loss of lung function occurs quickly in postmenopausal women. 27,28 Estrogen along with progesterone has been associated with airway smooth muscle relaxation which reduces the contractile response of these respiratory muscles. 29~31 Estrogen could play a crucial role in collagen production. 32 Results from our study suggest that women tend to develop obstructive pattern of ventilatory dysfunction and will add to the data on biological role of the ovarian hormones in modulating airways. Specific health education strategies have to be made to deal with the health problems faced by women after menopause.

Limitations
The sample size and exclusion criteria of this study could limit its applicability for all women. Hormone levels, computed tomography, lung biopsy and lung diffusing capacity of carbon monoxide (DLCO) were not part of the study due to resource constraints.