Decreased clinic visits for acute respiratory infections following an adult tonsillectomy: A population-based study

Accepted Manuscript Decreased clinic visits for acute respiratory infections following an adult tonsillectomy: A population-based study

Shiu-Dong Chung, Shih-Han Hung, Herng-Ching Lin, KuanChen Chen PII: DOI: Reference:

S0196-0709(17)30280-6 doi: 10.1016/j.amjoto.2017.05.004 YAJOT 1860

To appear in: Received date: Revised date: Accepted date:

6 April 2017 ###REVISEDDATE### ###ACCEPTEDDATE###

Please cite this article as: Shiu-Dong Chung, Shih-Han Hung, Herng-Ching Lin, KuanChen Chen , Decreased clinic visits for acute respiratory infections following an adult tonsillectomy: A population-based study, (2017), doi: 10.1016/j.amjoto.2017.05.004

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT

Decreased Clinic Visits for Acute Respiratory Infections Following an Adult Tonsillectomy: A Population-based Study

Shiu-Dong Chung MD1,2,3, Shih-Han Hung MD4,5, Herng-Ching Lin PhD3,6, Kuan-Chen Chen PhD6

Department of Surgery, Far Eastern Memorial Hospital, Banciao, Taipei, Taiwan

2

Graduate Program in Biomedical Informatics, College of Informatics, Yuan-Ze

RI

PT

1

University, Chung-Li, Taiwan

Sleep Research Center, Taipei Medical University Hospital, Taipei, Taiwan

4

Department of Otolaryngology, Taipei Medical University Hospital, Taipei, Taiwan;

5

Department of Otolaryngology, School of Medicine, Taipei Medical University,

6

School of Health Care Administration, Taipei Medical University, Taipei, Taiwan

MA

NU

SC

3

Corresponding author: Herng-Ching Lin, School of Health Care Administration, Taipei Medical University, 250 Wu-Hsing St., Taipei 110, Taiwan, Tel: 886-2-6638-

PT E

D

2736 ext. 1006; E-mail: [email protected]

Shih-Han Hung, Herng-Ching Lin and Kuan-Chen Chen have equal contributions to

CE

this study

Running title: Clinic Visits Following a Tonsillectomy

AC

Funding sources: This research received no specific grant from any funding agency from the public, commercial, or not-for-profit sectors. Conflict of Interest Disclosure: None

1

ACCEPTED MANUSCRIPT

ABSTRACT Purpose: This study attempted to investigate the effects of a tonsillectomy on utilization of medical resources for acute respiratory infections by comparing numbers

PT

and costs of clinic visits within 1 year before and after a tonsillectomy.

RI

Materials and Methods: Data for this study were retrieved from the Taiwan

SC

Longitudinal Health Insurance Database 2005. The study includes 481 patients aged

NU

18~80 years who underwent a tonsillectomy and 481 comparison patients. A multivariate regression model employing difference-in-difference was carried out to

MA

assess the independent association between a tonsillectomy and the number and costs

D

of clinic visits.

PT E

Results: We found that for patients who underwent a tonsillectomy, the mean number of clinic visits for acute respiratory care 1 year before and after the index date

CE

significantly decreased from 7.3 to 4.2 (p<0.001). However, for the comparison group,

AC

there was no significant difference in the number (p=0.540) or costs (p=0.221) of clinic visits for acute respiratory care 1 year before and after the index date. A multivariate regression model revealed that a tonsillectomy was associated with a reduction of 3.38 in the mean number of clinic visits for acute respiratory care (p<0.001). In other words, a tonsillectomy reduced by 46.3% (3.38/7.3) the number of clinic visits for acute respiratory care after adjusting for sociodemographic 2

ACCEPTED MANUSCRIPT

characteristics and medical comorbidities compared to comparison patients. Conclusions: This study demonstrated that a tonsillectomy was of substantial benefit to adult patients in that it provides decreased healthcare utilization for acute respiratory

PT

infections.

AC

CE

PT E

D

MA

NU

SC

RI

Key Words: tonsillectomy; acute respiratory infection; epidemiology

3

ACCEPTED MANUSCRIPT

1. INTRODUCTION A tonsillectomy is one of the most commonly surgical procedures performed on both children and adults. More than 530,000 ambulatory procedures are performed

PT

annually in children aged less than 15 years in the United States [1]. Surgical rates,

RI

however, vary considerably across countries, from 1.9 per thousand children in Canada

SC

to 11.8 in Northern Ireland in 1998 [2]. The disparity in the frequency of

NU

tonsillectomies that exists annually worldwide may be due to a lack of consistent and sufficient evidence about the benefits of this procedure. Therefore, there is a need to

MA

determine measurable benefits of this common operation.

D

A number of studies have explored the potential benefits of a tonsillectomy in

PT E

patients with obstructive sleep apnea [3-6], chronic rhinosinusitis [7-9], recurrent throat infection [10,11], deep neck infection [12], and otitis media [13-15]. Evidence

CE

for the effectiveness of a tonsillectomy was shown in some studies, but the impact of a

AC

tonsillectomy is still inconclusive and is an area of debate [16,17]. In addition, healthcare service utilization following a tonsillectomy has recently garnered lots of attention. Some researchers reported a decreased number of physician visits for chronic tonsillitis or respiratory infections following a tonsillectomy [18-23]. However, almost all such studies only used questionnaires to explore healthcare service utilization following the tonsillectomy, and the results of survey studies may be 4

ACCEPTED MANUSCRIPT

compromised by recall bias. Furthermore, the majority of relevant studies only reported the healthcare utilization of patients who underwent a tonsillectomy alone, and almost no study has attempted to compare differences in healthcare utilization

PT

between patients who did and did not undergo a tonsillectomy. The lack of a

RI

comparison group would not allow clinicians or policy makers to understand the

SC

magnitude of the reduction in healthcare use following a tonsillectomy.

NU

Therefore, using population-based data from Taiwan over a 2-year period, we examined the number and costs of clinic visits for acute respiratory infections before

AC

CE

PT E

D

MA

and after an adult tonsillectomy using a difference-in-difference model.

5

ACCEPTED MANUSCRIPT

2. METHODS 2.1 Database Data for this study were retrieved from the “Longitudinal Health Insurance

PT

Database 2005” (LHID2005). The LHID2005 includes registration files and original

RI

medical claims for 1,000,000 enrollees randomly selected from all enrollees listed in

SC

the 2005 Registry of Beneficiaries under the Taiwan National Health Insurance (NHI)

NU

program (n=23.72 million). Numerous researchers have employed the LHID2005 to longitudinally follow-up utilization of medical services for these selected 1,000,000

MA

enrollees and published their study results in internationally peer-reviewed journals.

D

Therefore, the LHID2005 provides a unique opportunity to identify the relationship

PT E

between a tonsillectomy and healthcare service utilization for acute respiratory infections among adults.

CE

This study was exempt from full review by the Institutional Review Board of

AC

Taipei Medical University (TMU-JIRB 201612027) since the LHID2005 consists of de-identified secondary data released to the public for research purposes. 2.2 Study sample This study included a study group and a comparison group. We identified and selected 569 patients who had undergone a tonsillectomy (ICD-9-CM procedure code 28.2 or 28.3) between January 1, 2002 and December 31, 2012 as the study group. We 6

ACCEPTED MANUSCRIPT

excluded 86 patients aged <18 years and 2 patients aged >80 years old. As a result, 481 patients who had undergone a tonsillectomy were included as the study group. We then assigned the date of receiving the tonsillectomy as the index date.

PT

For the comparison group, we retrieved comparison patients from the remaining

RI

enrollees aged between 18 and 80 years of age in the registry of beneficiaries of the

SC

LHID2005. We further randomly selected 481 patients (one for every patient who

NU

underwent a tonsillectomy) matched with the study group by sex, age, and the year of the index date with the SAS proc survey select program (SAS System for Windows, vers.

MA

8.2, SAS Institute, Cary, NC). In this study, the year of the index date was the year in

D

which the study group underwent a tonsillectomy. Comparison patients were selected by

PT E

matching them to a given adult who underwent a tonsillectomy simply on their utilization of medical services in the same index year of that particular patient.

CE

Thereafter, we assigned the date of their first healthcare use occurring in the index year as

AC

the index date for the comparison group. Ultimately, 962 sampled patients were included in this study. We then calculated the mean number and costs of clinic visits for acute respiratory infections (ICD-9-CM codes 460~466) for each patient within the 1-year period before and after their index date. 2.3 Statistical analysis 7

ACCEPTED MANUSCRIPT

We used the SAS statistical package (SAS System for Windows, vers. 8.2) to perform the statistical analyses in this study. Paired t-tests were used to compare the difference in the mean number and costs of clinic visits within 1 year before and after

PT

the index date. Then a multiple regression employing difference-in-difference was

RI

carried out to assess the independent association between a tonsillectomy and the

SC

number and costs of clinic visits after adjusting for age, sex, geographic region, and

NU

residential urbanization level. The difference-in-difference estimate of the impact of a tonsillectomy on the number and costs of clinic visits was captured by the interaction

MA

term between a tonsillectomy and time period (before vs. after). It measures

D

differences in the number and costs of clinic visits before and after a tonsillectomy for

PT E

the study group compared to changes in the comparison group. Differences were

AC

CE

considered significant for two-sided p values of ≤0.05.

8

ACCEPTED MANUSCRIPT

3. RESULTS For the 962-person study sample, the mean age was 39.2 (±14.6) years, while they were 39.1 years for patients who underwent a tonsillectomy and 39.4 years for

PT

comparison patients (p=0.726) (Table 1). After matching for sex, age, and the year of

RI

the index date, there was no significant difference in geographic region between

SC

patients who underwent a tonsillectomy and comparison patients (p=0.069). However, there were significant differences in urbanization level (p=0.001) and monthly income

NU

(p<0.001) between patients who underwent a tonsillectomy and comparison patients.

MA

Table 2 present the mean number and costs of clinic visits for acute respiratory

D

care within 1 year before and after the index date for patients who underwent a

PT E

tonsillectomy and comparison patients. For patients who underwent a tonsillectomy, the mean number of clinic visits for acute respiratory care 1 year before and after the

CE

index date significantly decreased from 7.3 to 4.2 (p<0.001). Correspondingly, the

AC

mean costs of clinic visits for acute respiratory care 1 year before and after the index date also significantly decreased from New Taiwan (NT)$2929 to NT$1563 (p<0.001) (The average exchange rate in 2015 was US$1.00≈New Taiwan (NT)$32). However, for the comparison group, there was no significant difference in the number (p=0.540) or costs (p=0.221) of clinic visits for acute respiratory care 1 year before and after the index date. 9

ACCEPTED MANUSCRIPT

In Table 3, a multiple regression employing difference-in-difference confirmed the impact of a tonsillectomy on clinic utilization. As shown in Table 3, after adjusting for patients’ age, sex, urbanization level, monthly income, and geographic

PT

region, the coefficients of the interaction terms for the number of clinic visits for

RI

acute respiratory care were statistically significant and negative (p<0.001); a

SC

tonsillectomy was associated with a reduction of 3.38 in the mean number of clinic visits for acute respiratory care. In other words, a tonsillectomy reduced the number

NU

of clinic visits for acute respiratory care by 46.3% (3.38/7.3) after adjusting for

MA

sociodemographic characteristics and medical comorbidities compared to comparison

D

patients. Similarly, a tonsillectomy was negatively associated with the costs of clinic

AC

CE

PT E

visits for acute respiratory care (p<0.001).

10

ACCEPTED MANUSCRIPT 4. DISCUSSION Tonsillectomies are frequently performed, but controversy has continued to surround this procedure. In this large-scale analysis of healthcare service utilization

PT

after a tonsillectomy, we found that a tonsillectomy was associated with a 46.3% reduction in the mean annual number of clinic visits for acute respiratory infections

RI

after adjusting for sociodemographic characteristics and medical comorbidities

SC

compared to comparison patients. This indicates that the potential benefits of a

NU

tonsillectomy may actually be related to reduced healthcare utilization for acute

MA

respiratory infections. Despite these finding not necessarily supporting the role of a tonsillectomy as primary prevention, a tonsillectomy should be considered when

PT E

D

evaluating resource utilization that drives healthcare costs in patients with acute respiratory infections.

CE

Our study results were in accordance with results of previous studies which

AC

consistently reported reduced healthcare utilization following a tonsillectomy [18-23]. For example, a study by Bhattacharyya et al. found that the mean number of physician visits for chronic tonsillitis decreased from 5.8 to 0.3 within 12 months before and after a tonsillectomy in 65 patients aged between 16 and 60 years in the US [18]. Another study by Senska et al. observed that there was a significant decrease between the preoperative and postoperative mean numbers of physician visits for a sore throat

11

ACCEPTED MANUSCRIPT

(from 5 to 0.7) on 114 patients in Germany [21]. Nikakhlagh et al. found a decrease in days off work (from a mean of 27.6 to 1.3 days) and in the frequency of visits to a general practitioner following a tonsillectomy or adenotonsillectomy (from a mean of

PT

7.9 to 0.4 visits) in 812 adults and children in India [20]. In addition, one study by

RI

Wikstén J et al. found that a tonsillectomy alone saved approximately €3000 per year

SC

in self-reported costs of healthcare services in 124 patients in Finland [19]. Another study also reported that the mean costs related to the use of healthcare services during

NU

3 months preceding a tonsillectomy diminished from €538 at the baseline to €113 at 6

MA

months (p = 0.007) in 39 adolescents [22]. The above studies all used patient-reported

D

survey methods to assess the potential economic benefits of a tonsillectomy, so they

PT E

may suffer from recall bias. Furthermore, their results are not conclusive due to the lack of a control group and lack of randomization.

CE

This study used Taiwan’s NHI database to perform a population-based

AC

evaluation. The salient feature is that this claims data cover more than 98% of Taiwan’s enrollees and are generally considered to provide the most precise information on medical service utilization. Meanwhile, changes in the number and costs of clinic visits were estimated using a difference-in-difference analysis, including controls for possible confounding factors, which strengthens previous economic analyses. Furthermore, our current study adds important data regarding the 12

ACCEPTED MANUSCRIPT

magnitude of the reduction in healthcare services following a tonsillectomy. To the best of our knowledge, no such analysis has been presented in the past, and we believe that it could add a new perspective to the current evidence and offer promising

PT

directions for future research. Nevertheless, this population-based study suggests that

RI

a tonsillectomy has beneficial effects on clinic visits.

SC

Some limitations should be considered when interpreting the present results. First, the evidence indicates that a tonsillectomy is on average effective at reducing

NU

the frequency of clinic visits for acute or non-acute respiratory infection. However,

MA

detection of reduced clinic visits for related complications including sinusitis,

D

tonsillitis, and otitis media could not be specifically explored. Second, the current

PT E

ICD-9-CM diagnosis codes do not provide sufficient clinical specificity to describe the severity or complexity of acute respiratory infections. It is unclear whether

CE

patients who were more severely affected may have been more likely to benefit if they

AC

underwent a tonsillectomy. Third, the readers should be aware that based on a health insurance database, it would be difficult to precisely separate those receiving the tonsillectomy because of repeated infection, sleep-disordered breathing, or other conditions. However the main purpose of this study was to reveal the possible impact following an adult tonsillectomy and although the indication for these patients might be different, the significance of the result remains unaffected. Finally, results of our 13

ACCEPTED MANUSCRIPT

study conducted in a single country, a vast majority of whom are of Chinese ethnicity, cannot necessarily be generalized to other ethnic groups. Despite these limitations, this study demonstrated that a tonsillectomy was of

PT

substantial benefit to adult patients in that it provided decreased healthcare utilization

RI

for acute respiratory infections. The current findings could help clinicians and patients

AC

CE

PT E

D

MA

NU

SC

in determining the necessity and appropriateness of a tonsillectomy.

14

ACCEPTED MANUSCRIPT

This research did not receive any specific grant from funding agencies in the public,

AC

CE

PT E

D

MA

NU

SC

RI

PT

commercial, or not-for-profit sectors.

15

ACCEPTED MANUSCRIPT

REFERENCES [1]. Baugh RF, Archer SM, Mitchell RB, et al. Clinical Practice Guideline: Tonsillectomy in Children. Otolaryngol Head Neck Surg 2011;144:S1-30.

PT

[2]. Van Den Akker EH, Hoes AW, Burton MJ, Schilder AG. Large international

RI

differences in (adeno) tonsillectomy rates. Clin Otolaryngol Allied Sci

SC

2004;29:161-4.

[3]. Ye J, Liu H, Zhang GH, Li P, Yang QT, Liu X, Li Y. Outcome of

NU

Adenotonsillectomy for Obstructive Sleep Apnea Syndrome in Children. Ann

MA

Otol Rhinol Laryngol 2010;119:506-13.

D

[4]. Bhattacharjee R, Kheirandish-Gozal L, Spruyt K, et al. Adenotonsillectomy

PT E

Outcomes in Treatment of Obstructive Sleep Apnea in Children A Multicenter Retrospective Study. Am J Respir Crit Care Med 2010;182:676-83.

CE

[5]. Stewart MG, Glaze DG, Friedman EM, Smith EO, Bautista M. Quality of Life

AC

and Sleep Study Findings After Adenotonsillectomy in Children With Obstructive Sleep Apnea. Arch Otolaryngol Head Neck Surg 2005;131:308-14. [6]. Díez-Montiel A, de Diego JI, Prim MP, et al. Quality of life after surgical treatment of children with obstructive sleep apnea: Long-term results. Int J Pediatr Otorhinolaryngol 2006;70:1575-9.

16

ACCEPTED MANUSCRIPT

[7]. Brietzke SE, Brigger MT. Adenoidectomy outcomes in pediatric rhinosinusitis: A meta-analysis. Int J Pediatr Otorhinolaryngol 2008;72: 1541-5. [8]. Felisati G, Ramadan H. Rhinosinusitis in children: the role of surgery. Pediatr

PT

Allergy Immunol 2007;18 Suppl 18:68-70..

RI

[9]. Ungkanont K, Damrongsak S. Effect of adenoidectomy in children with complex

SC

problems of rhinosinusitis and associated diseases. Int J Pediatr Otorhinolaryngol 2004;68: 447-51.

NU

[10]. Paradise JL, Bluestone CD, Colborn DK, et al. Tonsillectomy and

MA

Adenotonsillectomy for Recurrent Throat Infection in Moderately Affected

D

Children. Pediatrics 2002;110:7-15.

PT E

[11]. Fujihara K, Koltai PJ, Hayashi M, Tamura S, Yamanaka N. Cost-Effectiveness of Tonsillectomy for Recurrent Acute Tonsillitis. Ann Otol Rhinol Laryngoly

CE

2006;115: 365-9.

AC

[12]. Wang YP, Wang MC, Lin HC, Lee KS, Chou P. Tonsillectomy and the Risk for Deep Neck Infection—A Nationwide Cohort Study. PLoS One 2015;10:e0117535. [13]. Rosenfeld RM, Culpepper L, Yawn B, Mahoney MC. Otitis media with effusion clinical practice guideline. Am Fam Physician 2004;69:2776, 2778-9.

17

ACCEPTED MANUSCRIPT

[14]. Casselbrant ML, Mandel EM, Rockette HE, et al. Adenoidectomy for otitis media with effusion in 2–3-year-old children. Int J Pediatr Otorhinolaryngol 2009;73:1718-24

PT

[15]. Oomen KPQ, Rovers MM, van den Akker EH, et al. Effect of

RI

adenotonsillectomy on middle ear status in children. Laryngoscope 2005;115:

SC

731-4.

[16]. Stuck BA, Windfuhr JP, Genzwürker H, et al. Tonsillectomy in Children. Dtsch

NU

Arztebl Int 2008;105: 852–61.

MA

[17]. Shay S, Shapiro NL, Bhattacharyya N. Revisit rates and diagnoses following

D

pediatric tonsillectomy in a large multistate population Revisits after Pediatric

PT E

Tonsillectomy. Laryngoscope 2015;125: 457-61. [18]. Bhattacharyya N, Kepnes LJ, Shapiro J. Efficacy and quality-of-life impact of

CE

adult tonsillectomy. Arch Otolaryngol Head Neck Surg 2001;127:1347-50.

AC

[19]. Wikstén J, Blomgren K, Roine RP, Sintonen H, Pitkäranta A. Effect of tonsillectomy on health-related quality of life and costs. Acta Otolaryngol 2013;133:499-503. [20]. Nikakhlagh S, Rahim F, Boostani H, Shirazi ST, Saki N. The effect of Adenotonsillectomy on quality of life in adults and pediatric patients. Indian J Otolaryngol Head Neck Surg 2012;64:181-3. 18

ACCEPTED MANUSCRIPT

[21]. Senska G, Ellermann S, Ernst S, Lax H, Dost P. Recurrent tonsillitis in adults: quality of life after tonsillectomy. Dtsch Arztebl Int 2010;107:622-8. [22]. Nokso-Koivisto J, Blomgren K, Roine RP, Sintonen H, Pitkäranta A. Impact of

PT

tonsillectomy on health-related quality of life and healthcare costs in children and

RI

adolescents. Int J Pediatr Otorhinolaryngol 2014;78:1508-12.

SC

[23]. Tsou YA, Lin CC, Lai CH, et al. Does Adenotonsillectomy really reduced clinic visits for pediatric upper respiratory tract infections? A national database study in

NU

Taiwan. Int J Pediatr Otorhinolaryngol 2003;77: 677-81.

MA

[24]. van den Aardweg MTA, Boonacker CWB, Rovers MM, Hoes AW, Schilder-

D

AGM. Effectiveness of adenoidectomy in children with recurrent upper

PT E

respiratory tract infections: open randomised controlled trial. BMJ 2011;343:d5154.

CE

[25]. Erickson BK, Larson DR, St Sauver JL, Meverden RA, Orvidas LJ. Changes in

AC

incidence and indications of tonsillectomy and T&A, 1970–2005. Otolaryngol Head Neck Surg 2009;140: 894–901.

19

ACCEPTED MANUSCRIPT

Table 1 Demographic characteristics of sampled patients (N=962) Patients who underwent a tonsillectomy

Comparison patients N=481

N=481

Variable

Column %

Total no.

Column %

239

49.7

239

49.7

Age, mean, SD (years)

39.1 ± 14.2

Urbanization level 28.1

2

134

27.9

3

91

18.9

4

65

13.5

5 (least)

56

11.6

≤ NT$15,840

194

NT$15,841~25,000 ≥ NT$25,001

Southern Eastern

AC

Central

0.001

168

34.8

135

28.1

64

13.3

57 57

11.9 11.9 <0.001

234

48.7

178

37.0

128

26.6

109

22.7

119

24.7

D

CE

Northern

0.726

40.3

PT E

Geographic region

MA

Monthly income

39.4 ± 14.9

SC

135

NU

1 (most)

>0.999

RI

Male

PT

Total no.

p value

0.069

251

52.2

251

52.2

123

25.6

104

21.6

94

19.5

114

23.7

13

2.7

12

2.5

Note: The average exchange rate in 2015 was US$1.00≈New Taiwan (NT)$32.

20

ACCEPTED MANUSCRIPT Table 2 Number of clinic visits within 1 year by patients who underwent a tonsillectomy and comparison patients Before

After

Difference

Variable Mean

SD

Mean

SD

7.3

8.6

4.2

Comparison patients

2.6

7.5

2.8

2979

3454

Costs of clinic visits for acute respiratory infections (NT$) Patients who underwent a tonsillectomy Comparison patients

851

SD

I R

-3.2

6.5

<0.001

3.7

0.2

6.7

0.540

1563

2115

-1416

2829

<0.001

1007

1391

156

2299

0.221

SD, standard deviation.

D E

SC

U N

A M

2419

T P E

C C

A

21

p value

Mean

Number of clinic visits for acute respiratory infections Patients who underwent a tonsillectomy

Paired t-tests

5.5

T P

ACCEPTED MANUSCRIPT Table 3. Multiple regression difference-in-difference estimates of the impacts of a tonsillectomy on the number and costs of clinic visits for acute respiratory infections Number of clinic visits

Log(costs) of clinic visits

for acute respiratory

for acute respiratory

infections

infections SE

4.70***

0.43

0.79***

0.08

0.23

0.42

-3.38***

0.60

-0.00

Males

-0.78*

0.08

-0.49***

0.11

0.01

-0.00

0.00

0.30

-0.17*

0.05

0.04

NU

Age

PT

Patients who underwent a tonsillectomy* time period

Estimate

RI

Time period (after vs. before)

SE

SC

Patients who underwent a tonsillectomy

Estimate

Urbanization level

MA

1 (most urbanized)

-0.55

0.40

-0.09

0.07

0.47

0.48

0.07

0.09

-0.04

0.55

-0.11

0.09

-1.36*

0.55

-0.20*

0.10

0.95*

0.42

0.15*

0.07

0.15

0.40

0.08

0.07

1.03

0.97

0.31

0.18

NT$15,841~25,000

0.10

0.37

0.02

0.06

≥ NT$25,001

0.02

0.40

0.06

0.07

2 3

Geographic region

Central Southern

AC

Eastern

CE

Northern

PT E

5 (least urbanized)

D

4

Monthly income ≤ NT15,840

Note: The average exchange rate in 2015 was US$1.00≈New Taiwan (NT)$32. SE, standard error.

22