Prevention of Benign Paroxysmal Positional Vertigo with Vit D Supplementation: A Randomized Trial

Seong-Hae Jeong, MD, PhD, 1 Ji-Soo Kim, MD, PhD, 2, 3 Hyo-Jung Kim, PhD, 4
Jeong-Yoon Choi, MD, PhD 3 Ja-Won Koo, MD, PhD, 3,5 Kwang-Dong Choi, MD, PhD, 6
Ji-Yun Park, MD, PhD, 7 Seung-Han Lee, MD, PhD, 8 Seo-Young Choi, MD, PhD, 6
Sun-Young Oh, MD, PhD, 9 Tae-Ho Yang, MD, 9 Jae Han Park, MD, 10 Ileok Jung, MD, 11
Soyeon Ahn, PhD, 12 Sooyeon Kim, MS. 12
Neurology® Published Ahead of Print articles have been peer reviewed and accepted for publication. This manuscript will be published in its final form after copyediting, page composition, and review of proofs. Errors that could affect the content may be corrected during these processes.

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1Department of Neurology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Korea
2Department of Neurology, Seoul National University College of Medicine, Seoul, Korea 3Dizziness Center, Seoul National University Bundang Hospital, Seongnam, Korea 4Research Administration Team, Seoul National University Bundang Hospital, Seongnam,
Korea
5Department of Otolaryngology, Seoul National University College of Medicine, Seoul, Korea
6Department of Neurology, Pusan National University Hospital, Pusan National University School of Medicine, Pusan, Korea
7Department of Neurology, Ulsan University College of Medicine, Ulsan University Hospital, Ulsan, Korea
8Department of Neurology, Chonnam National University Medical School, Gwangju, Korea 9Department of Neurology, Chonbuk National University School of Medicine, Jeonju, Korea 10Department of Neurology, School of Medicine, Catholic University of Daegu, Daegu,
Korea.
11Department of Neurology, Korea University Ansan Hospital, Ansan, Korea
12Medical Research Collaborating Center, Seoul National University Bundang Hospital, Seongnam, Korea

Character count for title: 96 Word count for the abstract: 226 Word count for the text: 3,006 Number of Figures: 3
Number of Tables: 4 Number of references: 39

Soyeon Ahn and Sooyeon Kim carried out the statistical analysis.

Corresponding author and reprints:

Ji-Soo Kim, MD, PhD.

email: [email protected]
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Editor’s Note

We discovered, after accepting this article that and well into our production process, that the randomized clinical trial was retrospectively registered by a few weeks. While this might seem like a minor detail, we think that the issue of prospective registration is crucially important to ensure unbiased reporting of clinical trials. Because of the late stage at which we discovered this oversight, we did not think that it would be fair to reject this paper, but we asked the authors to clarify the registration status of this study. We strive to identify any such irregularity earlier in the process.

Study funding

This study was supported by a grant of the Korea Healthcare Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (HI10C2020).

Disclosure

The authors report no disclosures relevant to the manuscript.

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Abstract

Objective

To assess the effect of vitamin D and calcium supplementation in preventing recurrences of benign paroxysmal positional vertigo (BPPV).
Methods

We performed an investigator-initiated, blinded-outcome-assessor, parallel, multicenter, randomized controlled trial in 8 hospitals between December 2013 and May 2017. Patients with confirmed BPPV were randomly assigned to the intervention (n=518) or the observation (n=532) group after a successful treatment with canalith repositioning maneuvers. The primary outcome was the annual recurrence rate (ARR). Patients in the intervention group had taken vitamin D 400 IU and 500 mg of calcium carbonate twice a day for one year when serum vitamin D level was lower than 20 ng/ml. Patients in the observation group were assigned to follow-ups without further vitamin D evaluation or supplementation.
Results

The intervention group showed a reduction in the ARR [0.83 (95% CI: 0.74-0.92) vs. 1.10 (95% CI: 1.00-1.19) recurrences per one-person year] with an incidence rate ratio of 0.76 (95% CI: 0.66-0.87, p<0.001) and an absolute rate ratio of -0.27 (-0.40 to -0.14) from intention to treat analysis. The number needed to treat was 3.70 (95% CI: 2.50-7.14). The proportion of patients with recurrence was also lower in the intervention than in the observation group (37.8 vs. 46.7%, p=0.005).
Conclusions

Supplementation of vitamin D and calcium may be considered in patients with frequent
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attacks of BPPV, especially when serum vitamin D is subnormal.

Classification of Evidence: This study provides Class III evidence that for patients with BPPV, vitamin D and calcium supplementation reduces recurrences of BPPV.

Abbreviations: ARR = Annual Recurrence Rate; aRR = a reduction in the ARR; BPPV = Benign Paroxysmal Positional vertigo; IRR = Incidence Rate Ratio 740 Y-P

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Introduction

Benign paroxysmal positional vertigo (BPPV) is characterized by brief attacks of vertigo that are induced by a change in head position with respect to gravity.1, 2 BPPV is ascribed to dislodged otoconia from the utricular macule entering into the semicircular canals.3-5 BPPV recurs frequently with an 1-10 year recurrence rate of 15-56%.6-8 Even though BPPV is a benign disorder, almost 86% of patients with BPPV suffer from interruptions in daily activities and lose days at work.7 Thus, the direct and indirect costs of BPPV are significant. The cost was estimated at about $2,000 to arrive at the diagnosis and management of BPPV in the USA.9 It was also reported that the healthcare costs associated with the diagnosis of BPPV alone approach $2 billion per year in the USA.10 At present, however, there are no established ways to prevent further attacks in this highly prevalent and recurrent disorder.10, 11 Recently, several studies have found higher prevalence of vitamin D deficiency/insufficiency and decreased bone mineral density in patients with BPPV than in normal controls.12-17 Even though anecdotal studies have reported prevention of recurrences of BPPV with supplementation of vitamin D,18, 19 no study adopted a prospective controlled trial. We conducted a multicenter, pragmatic, randomized, controlled trial to assess the effect
of vitamin D and calcium supplementation in preventing recurrences of BPPV.

Methods

Primary research question

This study aimed to determine the efficacy of vitamin D 400 IU and 500 mg of calcium carbonate twice a day for one year in reducing recurrences of BPPV using a randomized

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controlled trial. This phase IV study provides Class III evidence that for patients with BPPV, vitamin D and calcium supplementation reduces recurrences of BPPV.

Patients

The inclusion criteria for this study were designed to enroll the patients with confirmed and treated BPPV at the participating dizziness clinics. The patients should be ≥18 years of age.
A diagnosis of BPPV was based on 1) a history of recurrent brief attacks of vertigo or positional dizziness induced by head motion, 2) a typical positioning nystagmus characteristic of BPPV, and 3) not attributable to another disorder. When the nystagmus suggested that two or more canals were involved (different patterns of nystagmus depending on the provoking positional maneuvers), the mixed type BPPV was diagnosed.13 Key exclusion criteria include the planned use of vitamin D and/or calcium therapy, pregnancy, and a history of an allergic reaction, or a medically significant adverse reaction to the investigational product. All patients must provide written informed consent for participation.

Trial design

This is a multicenter, randomized, 1:1 parallel-group trial to assess the efficacy of oral administration of vitamin D 400 IU and 500 mg of calcium carbonate twice a day in reducing further attacks of BPPV after successful treatment with canalith repositioning maneuvers. This study was conducted at 8 university hospitals in South Korea. A total of 1,491 patients were screened for eligibility and 1,050 patients were randomized into either the intervention or the observation group from December 2013 to May 2016 (figure 1). The randomization was done using a concealed, computer-generated list of management assignment based on the
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predetermined simple randomization schedule provided by the central data management committee. The randomized patients had been followed for all clinical end points and serious adverse events with the primary and several secondary end point events confirmed by central adjudication blind to study assignment.

Standard Protocol Approvals, Registrations, and Patient Consents

The trial was registered at Clinicaltrials.gov (no., NCT02031692). This study was performed in accordance with ethical principles consistent with the Declaration of Helsinki, International Conference on Harmonization Good Clinical Practice guidelines, and applicable regulatory requirements. The final study protocol and informed consent were reviewed and approved by the corresponding health authorities and ethics boards/institutional review boards for all participating study sites. Enrolled patients gave written informed consent for participation in the trial. The first patient was enrolled on December 19th, 2013, and 17 patients were enrolled before the formal registration of the trial on January 8th, 2014, due to a delay in translation of the protocol in English for registration.

Sample size

Estimation showed that a sample size of 934 would have 80% power to detect a decrease in the frequency of BPPV recurrences by 20% with supplementation of vitamin D and calcium for 12 months at a 5% level of significance. The 20% relative risk reduction was based on consensus among the investigators who decided that, in the interest of vestibular disorder stewardship, increasing use of vitamin D and calcium for this common vestibular disorder should require strong justification. We assumed that recurrences of BPPV would follow a
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Poisson distribution and that a mean of 1.09 new recurrences of BPPV per person would be detected in the intervention group when an average rate of nonadherence was allowed up to 30%.

Intervention

The patients in the intervention group had evaluation of serum 25-hydroxyvitamin D, calcium, phosphorus, and parathyroid hormone, and had taken vitamin D 400 IU and 500 mg of calcium carbonate (CAVID CHEWABLE TAB, Takeda Pharmaceuticals, Nycomed) twice a day for one year when the serum vitamin D level was lower than 20 ng/ml. The adherence was monitored by counting the remaining tablets at each visit or by telephone interview throughout a year. Discontinuation of the supplementation due to adverse effects or other reasons was registered with the primary outcome data. Patients allocated to the observation group were arranged for follow-up without the blood tests and medication and were not allowed to take vitamin D or calcium as supplements during the follow-up. And those who received medication were asked to provide additional follow-up blood samples at Month 2 and Month 12.

Outcomes

The primary outcome measure was the total number of BPPV recurrences per patient (annual recurrence rate of BPPV per one-person year) at least one month after resolution of the initial attack. The initial primary outcome was the proportion of the patients who experienced recurrences during the follow-up. However, the primary outcome was changed into annual recurrence rate of BPPV on May 2016 since each patient may experience multiple
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recurrences during the study period and the proportion of patients with recurrences does not adequately reflect the main effect of preventive medication. This process was conducted with a guidance of an independent data monitoring committee responsible for monitoring safety and effect during the trial.
Secondary outcome measures included the proportion of the patients with recurrences during the follow-up, changes in serum 25-hydroxy vitamin D level, annual fall rate, annual fracture rate and the quality of life using University of California Los Angeles Dizziness Questionnaire (UCLA-DQ).
Using a hotline, the participants were instructed to telephone the study center whenever they suspected a recurrence of BPPV and were arranged to visit the nearest clinic at their earliest convenience to confirm a recurrence. Participants also had monthly telephone interviews regarding occurrences of vertigo, falling and fracture during the preceding month and quality of life at baseline, and 6 and 12 months after the enrollment using a uniform questionnaire.20 We determined the recurrences of BPPV based on confirmation of BPPV at the clinic during an attack or typical history of positional vertigo having occurred during the preceding month on the telephone interview;20 “Have you ever experienced rotational vertigo precipitated by head movement and resolved within minutes with the head still?” Even though the patients did not show BPPV at the clinic, the patients were considered to have suffered from a recurrence of BPPV when the patients reported a typical history of positional vertigo consistent with BPPV. This decision was based on frequent spontaneous resolution of BPPV without intervention. Thus, the determination of BPPV recurrences was based on either confirmation with examination at the participating centers or typical history of BPPV during the preceding month on monthly telephone interview.

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Safety criteria and adverse events

At each monthly follow-up, all adverse events were recorded and the relation of these events with the study drug was scored as “no relation,” “possible,” “probable,” or “definite.” The patients allocated to the intervention group had laboratory evaluation three times (at the baseline, and 2 and 12 months after initiation of the medication). The second evaluation two months after the initiation of therapy was also for measurement of serum calcium. When hypercalcemia (serum calcium > 10.5 mg/dl) was related to the symptoms of the gastrointestinal, cardiovascular, renal, and central nervous system, the study medication was discontinued.

Statistical considerations

Patients were kept in their originally assigned treatment groups for analysis. However, post- randomization losses to follow-up precluded a strict intent-to-treat analysis. We performed effect analyses on the intention-to-treat population that comprised all randomly assigned patients who had been followed up for at least one month (figure 1). The per protocol group analyses were also performed for the patients who completed a 12-month follow-up with more than 70% drug compliance. The model was built from the Poisson distribution, commonly used for model count data.21 Incidence rate ratio (IRR), a reduction in the ARR (aRR) and 95% confidence intervals were used to measure treatment efficacy. In additional exploratory subgroup analyses, we assessed the influence of potential risk factors for BPPV recurrences on the efficacy of vitamin D and calcium supplementation in preventing recurrences of BPPV.
A Poisson model was used to compare the recurrence rates between the intervention

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and observation groups. The models included an offset term to account for variation in the duration of follow-up. Kaplan-Meier methods were also used to construct cumulative time-to- event curves for the groups. All tests were performed using SAS Proc Genmod Software (SAS institute Inc., Cary, N.C.) and R statistical package (R project for Statistical Computing), and p < 0.05 was considered significant.

Data Availability

The data that support the findings of this study are available from the corresponding author, upon reasonable request.

Results

Study population

Of 1,050 participants who had been randomized in a 1:1 ratio, 957 (91.1%), 445 in the intervention group and 512 in the observation group, were able to complete the follow up at least for the first one month (table 1, figure 1). Thus, we analyzed 10,471.1 months (319,367 days) from these 957 patients (intention-to-treat population). The median follow-up duration was similar between the groups (365 days in the intervention vs. 362 days in the observation group). Overall, a total of 827 patients (78.8%) completed the study for a year, 79.8% in the intervention and 92.2% in the observation group. Overall, 90 in the intervention (90/445, 20.2%) and 40 in the observation group (40/512, 7.8%) opted out before the end of study, and had been followed up for 5.5 months in average (5.4 months in the observation vs. 5.7 months in the intervention group).

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Primary outcome

Supplementation of vitamin D and calcium significantly reduced the recurrences of BPPV [0.83 recurrences per one-person year (95% CI: 0.74-0.92) for the intervention vs. 1.10 (95% CI: 1.00-1.19) for the observation group]. This corresponds to an IRR of 0.76 (95% CI: 0.66 to 0.87) and an aRR of -0.27 (95% CI: -0.40 to -0.14) with the medication (p<0.001, table 2). The number needed to treat (NNT) was 3.70. Similar effects were also observed in per protocol group analyses [0.83 recurrences per one-person year (95% CI: 0.73-0.92) for the intervention vs. 1.12 (95% CI: 1.01-1.20) for the observation group, p<0.001]. Of interest, the effect of prevention was more prominent in those with decreased serum vitamin D at baseline (serum vitamin D < 20 ng/ml, table 3).
Subgroup analyses showed the preventive effect of medication irrespective of most of the clinical variables, except those younger than 65, without vascular risk factors, or with a history of migraine (P for interaction < 0.05 for all tests except the involved canals and types of BPPV, and ability for independent walking, figure 2).

Secondary outcome

The estimated proportion of patients with BPPV recurrences was higher in the observation group than in the intervention group (46.7 vs. 37.8%, p=0.005, table 2). Figure 3 demonstrates the first recurrences of BPPV in each group during the follow-up (p = 0.012).
The serum 25(OH)-vitamin D level had been increased from 13.3±3.9 at baseline to 24.4±7.7 ng/ml after two months and to 24.2±8.4 after one year of medication in those with supplementation of vitamin D (p<0.001, table 2). The frequencies of unexpected fall and fracture did not differ between the groups (p>0.05, table 2), and both groups showed a

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significant improvement in the quality of life scored with UCLA-DQ.

Adverse events

The table 4 lists the adverse events during the study. In the intervention group, two patients discontinued calcium supplementation due to hypercalcemia, two months after initiation of medication.

Discussion

In this study, daily supplementation of oral vitamin D and calcium carbonate significantly reduced recurrences of BPPV during the year of medication in patients with confirmed BPPV and lower serum vitamin D. Until now, canalith repositioning maneuvers have been the only verified treatments of BPPV when it occurred, and no medical treatments have been available to prevent recurrences in this highly prevalent and recurrent disorder.10, 11
Previous studies have suggested a role of impaired calcium metabolism in occurrences or recurrences of BPPV.12-19, 22-27 The otoconia, which cause BPPV when detached from the otoconial bed and trapped in the semicircular canal or attached to the cupula, is composed of calcium carbonate as calcite crystals and organic core consisting predominantly of glycoproteins.28 Calcium is required to mineralize the otoconia for maintenance of turnover.29, 30 All components of the epithelial Ca2+ channel transport system are expressed as a transcript in the semicircular canal ducts and cochlea, and some Ca2+ binding proteins are up-regulated by vitamin D.31 Previous studies also have demonstrated decreased density and increased size of otoconia in osteopenic/osteporotic rats.32 Furthermore, higher bone turnover rate and higher prevalence of accelerated metabolic bone diseases, such
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as osteoporosis, were reported in patients with BPPV.12-14, 16, 17 Therefore, supplementation of vitamin D and calcium would help restoring the healthy condition of otoconia in patients with vitamin D deficiency.
The design of the current study had the features of pragmatic trials. The adoption of this design made it possible to validate assessing serum vitamin D and supplementing vitamin D and calcium when vitamin D was deficient to reduce BPPV recurrences in a real-world setting. This study design allowed an avoidance of applying placebo to the patients with documented vitamin D deficiency, which could raise an ethical issue given the current dietary recommendation of calcium 500-1300 mg and vitamin D 400-600 IU per day.33 In view of the results of the current study, the efficacy would have been greater if the study medication were compared to placebo only in patients with BPPV and vitamin D deficiency.
Likewise in previous studies on nutritional supplements,34 a greater proportion of patients in the intervention group had failed to complete the follow-ups. To minimize the bias, however, we performed further analyses using 1) a Poisson model with an offset term to account for variation in the duration of follow-up, 2) the Kaplan-Meier methods to construct cumulative time-to-event curves for the groups, and 3) the per protocol group analysis. The results of all these additional analyses supported the preventive effect of vitamin D and calcium supplementation in BPPV recurrences. The rapid normalization of serum vitamin D after supplementation has been reported previously35 and was also confirmed in our study 2 months after initiation of supplementation. Thus, the high dropout rate in our study might have underestimated the preventive effect of vitamin D and calcium supplementation.
Of note, the baseline serum vitamin D level was higher in the patients included for analyses of medication effects than in those excluded (Data available at Dryad,Tables e1-2:

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https://doi.org/10.5061/dryad.sxksn0303). This might have created a bias, but the preventive effect of vitamin D/calcium supplementation was more prominent in those with lower levels of serum vitamin D in our study (table 3).
Since BPPV is not a life-threatening disorder, the potential benefit of supplementing vitamin D and calcium should be validated from the aspect of cost effectiveness. Patients with BPPV are known to bear an average expense of US $180 per individual in South Korea,36 $2,684.74 in the United States,9 $265.19 in the United Kingdom,37 and $439.99 in Spain.38 Since the NNT was 3.70 in our study, the average expense per BPPV attack should be compared with
3.70 X average per capita cost for intervention [costs for blood tests (serum vitamin D once and serum calcium twice) + 0.67* X cost of medication for one year in a person, *Only 67% of the patients in the intervention group took the medication] in each country. For example, the costs to reduce one BPPV attack are estimated at $132.96 in South Korea and at $346.53 in the USA (Data available at Dryad, Table e-3: https://doi.org/10.5061/dryad.sxksn0303), which is lower than the expenses for each BPPV attack.
It is interesting that those with migraine did not benefit from vitamin D and calcium supplementation compared to those without migraine; there is a fair amount of overlap between BPPV and atypical/ vestibular migraine, and this finding may suggest those with migraine may have been misclassified and instead had vestibular migraine.
Our study has several limitations. First, despite the trial of a pragmatic design, the absence of placebo control could be concerned. Second, there is a potential for misclassification of vertigo by questionnaire. Third, since this study was performed only in Korea, the potential effects of ethnicity should be considered. The association of serum vitamin D deficiency and BPPV has been established in Austria,18 Egypt,19 and China 27 as
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well as in Korea.15, 26 However, the causal role of vitamin D appears to be universal in BPPV. In this study, both vitamin D and calcium were administered since most consequences of vitamin D deficiency are the results of impaired mineral ion homeostasis,39 and the cost of combined vitamin D and calcium supplementation adopted in this study was lower than vitamin D supplementation alone in Korea. In the future, however, the effectiveness of supplementing both vitamin D and calcium should be compared to supplementing vitamin D alone. Furthermore, the optimal dosage of vitamin D supplementation and the target serum level of vitamin D should be determined in BPPV. The supplementation of vitamin D and calcium for one year significantly reduced the recurrences of BPPV in patients with decreased serum vitamin D. Thus, management of vitamin D deficiency should be considered in patients with frequent attacks of BPPV, especially when serum vitamin D is subnormal. The optimal dosage and duration of vitamin D supplementation and the target serum level should be determined in future studies.

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Acknowledgement

The authors thank Division of Statistics in Medical Research Collaborating Center at Seoul National University Bundang Hospital for statistical analyses. We also thank Prof. J. Patrick Barron for copyediting the manuscript.

18

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Supplementary material

Supplementary material is available at https://doi.org/10.5061/dryad.sxksn0303.

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Appendix 1: Authors

Name Location Contribution

Seong-Hae Jeong, MD, PhD
Ji-Soo Kim, MD, PhD
Hyo-Jung Kim, PhD
Jeong-Yoon Choi, MD, PhD
Ja-Won Koo, MD, PhD
Kwang-Dong Choi, MD, PhD
Ji-Yun Park, MD, PhD
Seung-Han Lee, MD, PhD
Seo-Young Choi, MD, PhD
Sun-Young Oh, MD, PhD

Chungnam National University Hospital designed the study; analysis and interpretation of the data; drafted the manuscript

Seoul National University Bundang Hospital supervised study; designed the study; analysis and interpretation of the data; drafted
the manuscript
Seoul National University Bundang Hospital directed the study; contributed to the acquisition of the data Seoul National University Bundang Hospital contributed to the acquisition and analysis of the data Seoul National University Bundang Hospital contributed to the acquisition and analysis of the data Pusan National University Hospital contributed to the acquisition and analysis of the data Ulsan University Hospital contributed to the acquisition and analysis of the data Chonnam National University Hospital contributed to the acquisition and analysis of the data Pusan National University Hospital contributed to the acquisition and analysis of the data Chonbuk National University Hospital contributed to the acquisition and analysis of the data

Tae-Ho Yang, MD Chonbuk National University Hospital contributed to the acquisition and analysis of the data
20

Jae Han Park, MD Catholic University of Daegu Hospital contributed to the acquisition and analysis of the data
Ileok Jung, MD Korea University Ansan Hospital contributed to the acquisition and analysis of the data
Soyeon Ahn, PhD Seoul National University Bundang Hospital contribution to analysis and interpretation of the data; drafted the manuscript
Sooyeon Kim, MS Seoul National University Bundang Hospital contribution to analysis and interpretation of the data

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Figure Legends

Figure 1. Study design

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Figure 2. Absolute rate reduction according to clinical variables.

Subgroup analyses showed the preventive effect of medication irrespective of most of the clinical variables except those younger than 65, without vascular risk factors, or with a history of migraine (P for interaction < 0.05 for all tests except the involved canals and types of BPPV, and ability for independent walking. The dashed vertical line represents the null hypothesis (aRR = 0). The unbroken vertical line marks the overall summary estimate (aRR
= -0.27).

aRR; a reduction in the annual recurrence rate

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Figure 3. Kaplan-Meier curves for the first recurrence of benign paroxysmal positional vertigo.
The Kaplan-Meier curves show that the experiment group has lower recurrences of BPPV than the control throughout study period (p = 0.012).

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Table 1. Baseline Characteristics.
Characteristics Intervention group Observation group P value
(N=445) (N=512)
Demographic

Age – year (mean±SD)
62.2 ± 11.7
61.6 ± 12.2
0.429
Sex – N (%) 0.642
men 162 (36.4) 179 (35.0)
women 283 (63.6) 333 (65.0)
Body mass index (mean±SD) 23.3 ± 2.9 23.8 ± 3.0 0.014
Clinical
BPPV type – N (%) 0.097
Posterior 297 (66.7) 330 (64.5)
Horizontal 130 (29.2) 172 (33.6)
Anterior 13 (2.9) 9 (1.8)
Mixed 5 (1.1) 1 (0.2)
N of repositioning maneuver 1.6 ± 0.9 1.6 ± 1.1 0.913
Previous dizziness – N (%) 239 (53.7) 274 (53.6) 0.978
Previous ear disease – N (%) 68 (15.3) 71 (13.9) 0.552
Current smoker – N (%) 39 (8.9) 44 (8.9) 0.990
Vascular risk – N (%) 176 (39.6) 208 (40.8) 0.698
Migraine – N (%) 111 (24.9) 117 (23.0) 0.479
Motion sickness – N (%) 115 (25.8) 125 (24.5) 0.636
Bone mineral density – N (%) 0.145
Osteoporosis 64 (14.4) 53 (10.4)
Normal 337 (75.7) 411 (80.3)
Unknown 44 (9.9) 48 (9.4)

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Independent walking – N (%) 432 (97.1) 499 (97.8) 0.451
UCLA-DQ (mean±SD) 13.5 ± 5.0 14.1 ± 4.9 0.083
N = number, SD = standard deviation, UCLA-DQ = UCLA Dizziness Questionnaire

There were no differences in the characteristics between the groups at baseline except higher body mass index in the observation group (p=0.014).

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Table 2. Primary and secondary outcome

Group

Relative

Absolute

P value

Intervention (N=445) Observation (N=512)

difference

difference

Primary Outcome
Annual recurrence rate (95% CI)a
0.83 (0.74 to 0.92)
1.10 (1.00 to 1.19)
0.76 (0.66 to 0.87)
-0.27 (-0.40 to -0.14)
< 0.001
Secondary Outcome
Proportion of BPPV recurrence (95% CI) 37.8% (33.3 to 42.3) 46.7% (42.4 to 51.0) 0.81 (0.70 to 0.94) -8.9% (-15.2 to -2.7) 0.005
Changes in serum vitamin D (ng/ml)b 13.3 (3.9) to 24.2 (8.4) NA NA +10.9 (10.0 to 11.9) < 0.001
Annual fall rate (95% CI)a 0.22 (0.17 to 0.27) 0.18 (0.14 to 0.21) 1.25 (0.93 to 1.69) 0.04 (-0.02 to 0.10) 0.14
Annual fracture rate (95% CI)a 0.03 (0.01 to 0.05) 0.03 (0.02 to 0.05) 0.93 (0.44 to 1.96) -0.002 (-0.03 to 0.02) 0.84
aAnnual recurrence/fall/fracture rates were calculated using Poisson regression analysis with an offset of duration.
bValues are the mean (standard deviation). CI = confidence interval, NA = not available

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Table 3. Comparison of annual recurrence rate according to serum vitamin D level in the intervention groupa

Outcome Group Relative difference Absolute difference P value
Normal (N=146) Decreased (N=299)
0.95 (0.79 to 1.11) 0.76 (0.65 to 0.87) 1.24 (1.00 to 1.56) 0.19 (0.01 to 0.38) 0.05
Normal(N=146) Observation (N=512)
0.95 (0.79 to 1.11) 1.10 (1.00 to 1.19) 0.87 (0.72 to 1.05) -0.15 (-0.34 to 0.04) 0.14
Decreased (N=299) Observation (N=512)

Annual recurrence rate 0.76 (0.65 to 0.87) 1.10 (1.00 to 1.19) 0.70 (0.59 to 0.82) -0.33 (-0.48 to -0.19) <0.001
(95% CI) Deficient (N=71) Insufficient (N=228)
0.60 (0.40 to 0.80) 0.81 (0.69 to 0.94) 0.74 (0.51 to 1.06) -0.21 (-0.45 to 0.02) 0.08
Deficient (N=71) Observation (N=512)
0.60 (0.40 to 0.80) 1.10 (1.0 to 1.19) 0.55 (0.39 to 0.77) -0.50 (-0.72 to -0.28) <0.001
Insufficient (N=228) Observation (N=512)
0.81 (0.69 to 0.94) 1.10 (1.0 to 1.19) 0.86 (0.79 to 0.94) -0.28 (-0.44 to -0.13) <0.001

aEach group was classified with the following criteria of serum 25(OH) vitamin D; normal, ≥ 20 ng/ml; insufficient, 10 ng/ml ≤ & < 20 ng/ml; deficient, < 10 ng/ml. The decreased group included both insufficient and deficient groups (< 20 ng/ml). CI = confidence interval

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Table 4. Adverse events
Adverse events Intervention group Control group
(N=445) (N=512)
≥ 1 Adverse eventsa 26 3
Withdrawals due to adverse events
Related to the study drug 8
Related to other adverse events 2
Deathb 0 3
Anorexia 1
dyspepsia 10
Constipation 5
Edema 3
Itching sense 2
Urticaria 1
Hypercalcemia 2
Loose stool 2

aPatients could have had one or more adverse events, which were reported by the patients themselves or by the investigators.
bThe causes of death were not related to the use of study medication. In control group, 2 patients died from intracranial hemorrhage and gallbladder cancer, and the cause was unknown in the remaining one

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