Vitamin D and Pelvic Floor Disorders in Women

Badalian SS, Rosenbaum PF: Obstet & Gyneoc (2010) 115(4): 795-803.

April 3, 2013

 Ann Dunbar PT, DPT, MS, WCS

Primary Aim:  (1) To estimate the prevalence of vitamin D insufficiency or deficiency in women with pelvic floor disorders (2) To evaluate possible associations between vitamin D levels and pelvic organ prolapse (vaginal bulge) (POP), female urinary incontinence and fecal incontinence.

 Subjects: Using data from the National Health and Nutrition Examination Survey (NHANES) collected 2005-2006.  Had data on 3 pelvic floor outcomes and vitamin D levels on 1,881 non-pregnant women.

 Study Design: Descriptive

 Methods:

• Demographic data collection as well as definitions for parity, urinary incontinence, POP, and vitamin D deficiency are described in study. 
• Diasorin’s radioimmunoassay method was used to measure vitamin D levels.
• Methodology included both household interviews of subjects by trained interviewers and mobile examination centers.

Definitions:

• Vitamin D deficiency:  25(OH)D level < 10 ng/mL
• Vitamin D insufficiency: 25(OH)D level 10 to 30 ng/mL
• Vitamin D levels between 30 to 80 ng/mL considered to be normal.

Data Analysis

Rao-Scott adjusted χ² test used to assess associations between demographics and age categories, pelvic floor disorders and age categories, and vitamin D categories across both pelvic floor disorders and demographics, individually and as a composite variable. Associations between vitamin D levels and pelvic floor disorders were studied utilizing logistic regression models.   Individuals with negative reports of UI comprised the comparison groups.  Separate models were utilized for all women ages 20 years and older and for women 50 and older for presence of urinary incontinence and pelvic floor disorders. For vaginal bulge and fecal incontinence, only 1 model was utilized due to small numbers of women reporting these problems.

Results

• Mean age of subjects 47.9 yrs. with age range being 20 to 85+. Cohort reports to be approximately 72% non-Hispanic white race.
• Education, BMI, parity, and race varied significantly by age group (20 t o 49 compared with 50 to >85).
• Women in 50 to 85 yr old group tended to have fewer years of school, more children, and more likely to report being non-Hispanic white than group 20 to 49yrs.

Vitamin D (25(OH)D) levels

• About 82% of cohort had insufficient Vit D levels (age groups not significantly different)

Pelvic floor disorders

• Increased with age (prevalence younger than 50=14% and prevalence 50 and older=34%)

Weighted prevalence of demographic factors within 2 Vit D levels (below normal vs. normal)

• Women with less than HS education more likely to be lower than women with at least some college
• NonHispanic whites more frequently in higher Vit D category
• Women with higher BMI had lower Vit D levels
• Prevalence of UI and 1 or more pf disorders significantly higher in group with Vit D below normal compared to group in normal Vit D range

Multivariate logistic regression analysis

Using categorical version of Vit D levels

Data for women 20 yrs and older

• Evaluated effect of Vit D level on presence or absence of pf disorder and controlling for race, age, BMI, parity, and education
• Results suggest a 6% significant decrease in risk of pf disorder for each 5-ng/mL increase in Vit D (P=.043)
• Increasing BMI and age predicted presence of pf disorder where education and parity did not

Using data for women 50 yrs and older

• Results similar for this group  suggesting an 8% decrease in risk with each 5-ng-/mL increase

Using UI as outcome in model:  Similar to above findings

• Increasing BMI and age significantly associated with increased risk for UI
• Vit D / UI association stronger in older women (45% risk reduction in UI with Vit D levels in normal range)

Fecal incontinence and vaginal bulge

• Findings not significant except for multivariate analysis of vaginal bulge (results suggest increased risk of vaginal bulge with increased levels of Vit D)
• Authors suggest FI and vaginal bulge are under-reported in this survey (this is common in symptom-based screening) and for vaginal bulge, a GYN exam is needed to be able to assess severity of POP problem (one of the limitations of this study)

Discussion

• Higher Vit D levels are associated with decreased risk for any pelvic floor disorder in all women (P=.043) and women over 50 (P=.039)
• In older women, a decreased risk of UI observed when Vit D levels were at least 30ng/ml and above and when factoring in BMI, age, education, race and parity, these associations remained consistent (P=.022)
• Contrary to expectation, vaginal bulge was reported more often in women with increased levels of Vitamin D

Clinical Application

This study suggests a simple lifestyle intervention for patients with pf dysfunction by assuring they have adequate dietary intake of Vit D  (RDA for ≥97.5% of the population is 600 IU/day for ages 1 to 70 years and 800 IU/day for those older than 71 yrs; Ross et al, 2011).

Extra Reading

Parker-Autry C, Burgio KL, Richter HE: Vitamin D status: a review with implications for the pelvic floor. Int Urolgynecol J. (2012); 23:1517-1526.

Highlights

Vitamin D Physiology and Importance of Supplementation

• Vital to many organisms and is one of the oldest known hormones
• Provitamin D in cell membrane produces Vit D when skin is exposed to ultraviolet B rays
• This circulating D3 is bound by Vit D circulating protein in serum and stored in adipose tissue or delivered to liver where it is converted to 25-hydroxyvitamin D2 (25(OH)D.
• In kidney, 25(OH)D is activated by conversion to calcitriol.
• Calcitriol and 25(OH)D synthesis is coupled with calcium homeostasis.
• Serum levels of Vit D are regulated by parathyroid hormone and calcium and phosphorus levels.
• Since only 100 to 200 IUs/day of Vit D come from natural and fortified food sources, sunlight exposure is the primary source

Vitamin D and Muscle Function

• Among many other tissues, Vit D receptors (VDR) are found present in skeletal muscles and they decrease with age
• “Vit D may be instrumental for skeletal muscle function efficiency by regulating calcium homeostasis to affect muscle contractility and by protecting the muscle cellular environment against insulin resistance and inflammation.”
• VDR have been identified in smooth muscle cells of urethra and bladder as well as urothelial cells of the bladder neck

Vitamin D and the Pelvic Floor and the Bladder

• Since etiology of pf dysfunction and POP is hypothesized to come from neurologic compromise, muscle weakness and fascial detachment, it is reasonable to consider that insufficient Vit D serum levels could impact intracellular calcium homeostasis thus impacting muscle contractility.
• Studies suggest an association between increased intake of dietary Vit D and decreased risk of OAB symptom onset (via abnormalities in bladder wall calcium homeostasis, weakened detrusor muscle, altered communication from the outer bladder cover, the urothelium, thought to be involved in communicating thermal, mechanical, and chemical information to the bladder)

Vitamin D and Pelvic Floor Muscle Training

• Maintaining Vit D at sufficient levels has been shown to increase skeletal muscle efficiency
• Additional research needed to confirm the role of Vit D on pfm function and the possible impact of Vit D supplementation on a pfm rehabilitation program for the management of symptoms