the prevalence of urinary incontinence ( ui ) is increased among older adults and is associated with poor quality of life , social isolation , falls , and depression(14 ) .
drug therapy for ui is associated with the potential for adverse events and , may have significant cost ; thus adherence is often maintained for only a few months(6 , 7 ) .
additional treatment modalities are needed in order to maximize the impact of multicomponent therapy and reduce the potential for adverse events .
recent studies have suggested a relationship between vitamin d and conditions increasing the risk of ui among both men and women .
vitamin d receptors are present in the bladder and striated muscle of the pelvic floor musculature(8 , 9 ) .
additionally , prostatic cells express 1-hydroxylase and can synthesize 1,25-di - hydroxyvitamin d ( the active form of vitamin d)(10 ) .
low vitamin d levels are associated with increased prevalence of pelvic floor disorders among women and moderate - to - severe ui in men(1113 ) . however , these studies are based on cross - sectional data .
one randomized controlled trial demonstrated treatment with a vitamin d analog reduced prostate enlargement in the setting of benign prostatic hyperplasia(14 ) .
evaluation of data assessing the longitudinal relationship between vitamin d and incident ui would allow for additional insights and provide next steps in determining the need for interventional studies .
thus , our aim was to evaluate the association of low vitamin d with incident ui in a cohort of community - dwelling older adults .
the university of alabama at birmingham study of aging ( soa ) is a longitudinal cohort study of community - dwelling older adults designed to assess factors associated with changes in mobility . between 1999 and 2001
the study recruited 1,000 individuals 65 years of age and older from five counties in west central alabama , including 3 rural counties and 2 urban counties .
individuals were randomly selected from medicare beneficiary lists stratified by race and gender so that the cohort included equal numbers of men and women , black and white , and urban and rural residence .
exclusion criteria included : inability to understand the recruiter , residing in nursing homes , or inability to independently coordinate an appointment for the baseline , in - home interview .
the institutional review board at the university of alabama at birmingham approved the study and written informed consent was obtained prior to beginning study procedures . at baseline and in 2004 , a two - hour , in - home assessment was performed , which included a medical history , cognitive screening test , screening for depression , assessment of activities of daily living , and questions regarding multiple facets of functional status .
eligibility for the in - home follow - up in 2004 was the same as the baseline evaluation with 624 of 733 ( 85.1% ) of surviving participants agreeing to the in - home assessment in 2004(15 ) .
these 624 participants were offered the opportunity to have a blood test obtained , and 408 ( 65.4% ) agreed to the lab test .
blood samples were used to measure multiple laboratory assays , but not vitamin d levels .
vitamin d analyses were completed in 2013 for 350 of the 408 ( 85.8% ) participants who had a blood sample obtained and had sufficient serum available for the vitamin d assays .
of these participants with vitamin d data available , 187 /350 ( 53.4% ) did not have ui in 2004 .
follow - up incident ui data were available on 175/187 ( 94.6% ) of these participants .
thus , prevalence of vitamin d deficiency and insufficiency was assessed using 350 participants ; while the 175 participants without ui in 2004 and with follow - up incident ui data were the focus of the current analysis .
every six to twelve months , participants were contacted by phone to complete a questionnaire including information about ui .
participants provided information about the presence of ui using the validated two - item incontinence severity index , which correlates well with ui measured with 24-hour pad weights and ui frequency on bladder diaries(16 ) .
participants were asked , have you ever leaked even a small amount of urine ? and how often does that occur ?
incident ui was classified as an affirmative response to the first question and a response to the second question of at least monthly ui .
analysis of serum concentrations of 25-hydroxyvitamin d [ 25(oh)d ] was performed on stored sera using an ids - isys analyzer . to ensure quality control of the vitamin d assay ,
the laboratory participates in the vitamin d external quality assessment scheme every 3 months and in the nist / nih vitamin d metabolites quality assurance program semi - annually . for the purposes of this evaluation ,
vitamin d deficiency was defined as a serum 25-hydroxyvitamin d level < 20 ng / ml and vitamin d insufficiency as a 25-hydroxyvitamin d level from 20 ng / ml to < 30 ng / ml .
descriptive statistics were used to analyze baseline characteristics of the subsample ( n=350 ) of uab study of aging participants for which sera were available for vitamin d assays in 2004 and the 175 participants who were included in the incident ui analysis .
multivariable logistic regression and cox proportional hazard models adjusted for age , gender , and race / ethnicity were utilized to evaluate the relationship between vitamin d status and incident ui among those participants reporting no ui at baseline .
all analyses were conducted using sas 9.2 ( sas institute , cary , nc ) .
the university of alabama at birmingham study of aging ( soa ) is a longitudinal cohort study of community - dwelling older adults designed to assess factors associated with changes in mobility . between 1999 and 2001
the study recruited 1,000 individuals 65 years of age and older from five counties in west central alabama , including 3 rural counties and 2 urban counties .
individuals were randomly selected from medicare beneficiary lists stratified by race and gender so that the cohort included equal numbers of men and women , black and white , and urban and rural residence .
exclusion criteria included : inability to understand the recruiter , residing in nursing homes , or inability to independently coordinate an appointment for the baseline , in - home interview .
the institutional review board at the university of alabama at birmingham approved the study and written informed consent was obtained prior to beginning study procedures . at baseline and in 2004 , a two - hour , in - home assessment was performed , which included a medical history , cognitive screening test , screening for depression , assessment of activities of daily living , and questions regarding multiple facets of functional status .
eligibility for the in - home follow - up in 2004 was the same as the baseline evaluation with 624 of 733 ( 85.1% ) of surviving participants agreeing to the in - home assessment in 2004(15 ) .
these 624 participants were offered the opportunity to have a blood test obtained , and 408 ( 65.4% ) agreed to the lab test .
blood samples were used to measure multiple laboratory assays , but not vitamin d levels .
vitamin d analyses were completed in 2013 for 350 of the 408 ( 85.8% ) participants who had a blood sample obtained and had sufficient serum available for the vitamin d assays .
of these participants with vitamin d data available , 187 /350 ( 53.4% ) did not have ui in 2004 .
follow - up incident ui data were available on 175/187 ( 94.6% ) of these participants .
thus , prevalence of vitamin d deficiency and insufficiency was assessed using 350 participants ; while the 175 participants without ui in 2004 and with follow - up incident ui data were the focus of the current analysis .
every six to twelve months , participants were contacted by phone to complete a questionnaire including information about ui .
participants provided information about the presence of ui using the validated two - item incontinence severity index , which correlates well with ui measured with 24-hour pad weights and ui frequency on bladder diaries(16 ) .
participants were asked , have you ever leaked even a small amount of urine ? and how often does that occur ?
incident ui was classified as an affirmative response to the first question and a response to the second question of at least monthly ui .
analysis of serum concentrations of 25-hydroxyvitamin d [ 25(oh)d ] was performed on stored sera using an ids - isys analyzer . to ensure quality control of the vitamin d assay ,
the laboratory participates in the vitamin d external quality assessment scheme every 3 months and in the nist / nih vitamin d metabolites quality assurance program semi - annually . for the purposes of this evaluation ,
vitamin d deficiency was defined as a serum 25-hydroxyvitamin d level < 20 ng / ml and vitamin d insufficiency as a 25-hydroxyvitamin d level from 20 ng / ml to < 30 ng / ml .
descriptive statistics were used to analyze baseline characteristics of the subsample ( n=350 ) of uab study of aging participants for which sera were available for vitamin d assays in 2004 and the 175 participants who were included in the incident ui analysis .
multivariable logistic regression and cox proportional hazard models adjusted for age , gender , and race / ethnicity were utilized to evaluate the relationship between vitamin d status and incident ui among those participants reporting no ui at baseline .
all analyses were conducted using sas 9.2 ( sas institute , cary , nc ) .
of the 350 participants who had serum samples available for vitamin d assays in 2004 ( the baseline year for this analysis ) ( table 1 ) , 54% were vitamin d deficient [ 25(oh)d < 20 ng / ml ] and 25% were vitamin d insufficient [ 25(oh)d 20 ng / ml to < 30 ng / ml ] ( table 1 ) . among the 187 subjects with no ui at baseline , 57% ( 107/187 ) were vitamin d deficient and 24% ( 45/187 ) were vitamin d insufficient .
for these 187 subjects , the mean baseline 25(oh)d level was 20.5 ng / ml  9.7 .
mean length of follow - up was 34.5 months ( range 6  42 ) .
for the 175 of the 187 subjects who had follow - up evaluation for incident ui over 42 months , incident ui occurred in 37% ( 65/175 , 37% of women and 38% of men ) .
these 175 participants generally reflected the demographic distribution of the original soa cohort and those included in a previous analysis of incident ui(17 ) . among those with vitamin d deficiency , 37/97 ( 38% ) developed ui and among those with vitamin d insufficiency , 20/44 ( 45% ) developed ui .
this compared to 8/34 ( 23% ) of those with sufficient levels of vitamin d. however , there was no statistically significant difference in the proportion of individuals developing incident ui during the study period by vitamin d status ( p=0.13 ) .
after adjustment for age , gender and race / ethnicity , cumulative incident ui at 42 months was associated with vitamin d insufficiency status at baseline [ aor 3.18 ( 95%ci 1.148.87 ) , p = 0.03 ] .
there was a trend toward association between baseline vitamin d deficiency and incident ui [ 2.47 ( 95%ci 0.936.53 ) , p=0.07 ] .
however , there was no association between vitamin d insufficiency or deficiency and time to incident ui in unadjusted ( log - rank p=0.19 ) or adjusted analyses ( cox model overall test of significance , p=0.14 ) .
these results suggest a potential association between vitamin d and the development of ui among a racially diverse cohort of older men and women .
an evaluation of the longitudinal association between vitamin d status and incident ui among older adults is novel .
previous cross - sectional data have suggested an association between low vitamin d status and lower urinary tract symptoms in men and women ; however , these studies are limited because they can not evaluate for causality(11 , 12 ) .
the university of alabama at birmingham soa is unique among longitudinal studies of aging populations because the study population is racially diverse , validated questionnaires were used to assess urinary symptoms , and stored serum samples were available .
there are several mechanisms by which vitamin d could exert influence on lower urinary tract function .
vitamin d receptors are present in the bladder and striated muscle of the pelvic floor musculature(8 , 9 ) .
skeletal muscle control and strength are vital for the voluntary control of the urethral sphincter and pelvic floor muscles and likely a significant factor in achieving continence .
a vitamin d analog was evaluated as a potential adjuvant treatment with tolterodine and demonstrated improved bladder capacity in an animal model of bladder outlet obstruction(18 ) .
additionally , prostatic cells express 1-hydroxylase and can synthesize 1,25 di - hydroxyvitamin d ( the active form of vitamin d)(10 ) .
a recent study found a specific polymorphism of the vitamin d receptor uniquely linked to a protective effect for the development of lower urinary tract symptoms in men(19 ) .
current treatment guidelines for ui care recommend lifestyle changes and behavioral therapy as a first step followed by bladder relaxant drug therapy(5 ) .
older adults are more susceptible to the anticholinergic adverse events from bladder drug therapy ( constipation , reflux , cognitive changes , xerostomia ) , which occur frequently with the most commonly prescribed bladder relaxants .
additionally , these drugs can be costly and many patients discontinue drug therapy after a few months(6 , 7 ) .
vitamin d is a low cost , well - tolerated supplement and could provide an adjuvant treatment to currently recommended exercise - based behavioral therapy .
the results from the study of aging showing more than half of participants were deficient in vitamin d and more than 80% were insufficient or deficient are consistent with population - based estimates(20 ) .
vitamin d has been implicated in multiple health conditions and the institute of medicine has called for additional studies to provide information about the role of vitamin d(21 ) .
longitudinal studies evaluating vitamin d replacement rarely include outcomes related to bladder health(22 , 23 ) .
the current results add to the growing body of literature focused on the potential for vitamin d status to impact the health of older adults .
the assessment of the association of vitamin d deficiency with ui may have been limited by the small number of persons with a baseline serum 25-hydroxyvitamin d level of 30 ng / ml or greater ( n=34 ) .
the cox proportional hazard analyses are limited because ui was reported every 612 months , which could lead to left censoring .
we were not able to ascertain if participants received interval non - pharmacologic treatments for their bladder symptoms during the 612 month assessments .
the uab study of aging was designed to assess factors impacting social mobility among community - dwelling older adults and did not query a comprehensive set of factors that might impact the development of incontinence in this population .
lastly , vitamin d could be a marker of better health and physical activity , which was not controlled for in this analysis .
urinary incontinence is a burdensome condition with significant impact on quality of life for many adults as they age .
treatment strategies for geriatric conditions such as ui are often multicomponent ; however , current drug therapy is limited because of the potential for adverse events and cost . these results
add to a growing body of literature suggesting physiologic mechanisms , cross - sectional association studies , and now preliminary longitudinal research demonstrating a potential association between vitamin d and optimal pelvic floor function .
vitamin d offers a low cost , well - tolerated option that warrants further evaluation in an interventional trial , particularly focused on a population of older adults with vitamin d insufficiency .
 objectiveto determine if vitamin d status is associated with incident urinary incontinence ( ui ) among community - dwelling older adults.methodsthe university of alabama at birmingham study of aging is a prospective cohort study of community - dwelling medicare enrollees . 
 standardized assessment of ui using the validated incontinence severity index . 
 analysis of 25-hydroxyvitamin d ( 25(oh)d levels was performed on stored baseline sera . 
 ui was assessed every 612 months for up to 42 months . 
 analyses included multivariable logistic regression and cox proportional hazard models.resultsof 350 participants ( 175 male , 147 black , mean age 73.6  5.8 ) , 54% ( 189/350 ) were vitamin d deficient [ 25(oh)d < 20 ng / ml ] and 25% ( 87/350 ) were vitamin d insufficient [ 25(oh)d 20 ng / ml to < 30 ng / ml ] . among the 187 subjects with no ui at baseline , 57% ( 107/187 ) were vitamin d deficient and 24% ( 45/187 ) were vitamin d insufficient . 
 175 of the 187 subjects had follow - up evaluation for incident ui over 42 months and incident ui occurred in 37% ( 65/175 ) . after adjustment cumulative incident ui at 42 months was associated with baseline vitamin d insufficiency ( p=0.03 ) and demonstrated a trend association with deficiency ( p=0.07 ) . 
 there was no association between baseline vitamin d status and time to incident ui.conclusionsthese preliminary results support an association between vitamin d and incident ui in community - dwelling older adults . 
 future studies may target specific at risk groups , such as men with bph or women with pelvic floor disorders for evaluation of the impact of vitamin d supplementation on urinary symptoms . 
INTRODUCTION
METHODS
Subjects
Urinary Incontinence Assessment
Vitamin D Assessment
Statistical Analysis
RESULTS
DISCUSSION
CONCLUSION
Supplementary Material