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Kim, Lee, Lee, and Chun: Differences between middle-aged and older people in association between income level and remaining teeth
Original Article

J Korean Acad Oral Health 2016;40(1):9-16.

Published online: 12 March 2016

DOI: https://doi.org/10.11149/jkaoh.2016.40.1.9

Differences between middle-aged and older people in association between income level and remaining teeth

Sun-Yi Kim1, Jeong-Keun Lee2, Yun-Hwan Lee3, Ki-Hong Chun3

1Suji Ida Dental CLinic, Suwon, Korea

2Department of Dentistry, School of Medicine, Ajou University, Suwon, Korea

3Department of Preventive Medicine & Public Health, School of Medicine, Ajou University, Suwon, Korea

Corresponding Author: Ki-Hong Chun Preventive Medicine & Public Health, School of Medicine, Ajou University, 164, World cup-ro, Yeongtong-gu, Suwon 16499, Korea Tel: +82-31-219-5082 Fax: +82-31-219-5084 E-mail: ajoujkh@ajou.ac.kr

Received 1 October 2015       Revised 3 February 2016       Accepted 12 February 2016

Copyright © 2016 Journal of Korean Academy of Oral Health

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objectives

To understand the relationship between monthly household income and number of remaining teeth as an indicator of oral health, and to find the differences between middle-aged and older people in this respect.

Methods

This study was conducted on data extracted from the Korean National Health & Nutrition Examination Survey, which surveyed all Korean citizens in 2012. From these data, data of 4502 people about 40 years of age who completed the questionnaires and examination survey were selected and analyzed. This study investigated the main factors affecting the remaining teeth, and analyzed the moderating effect of age on the relationship between income level and remaining teeth.

Results

The average number of remaining teeth was 25.17 for middle-aged people and 15.95 for older people, which was significantly different. The number of remaining teeth for middle-aged people showed a significant relationship with income level, education level, and smoking habit. The number of remaining teeth in older people was related to the same factors, along with an additional factor of whether or not they underwent oral examinations. From the interaction analysis conducted to find the moderating effect of age on the relationship between the number of remaining teeth and income level, the number of remaining teeth was more affected by income level in older people than in middle-aged people.

Conclusions

Income level was strongly related to oral health, particularly in older people. Therefore, it can be concluded that an oral health promotion policy is necessary for low-income people, particularly those in the older age group.

Keywords: Income level, Interaction, Moderating effect, Oral health inequalities, Remaining teeth

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Fig. 1.
The interaction of age and income level for the number of remaining teeth.
jkaoh-40-9f1.tif
Table 1.
Characteristics of the study subjects
Variable 40-65 (age)
 65≤ (age)
 Total
N (%) N (%) N (%)
Demographic characteristics Gender Male 1,152 (50.2) 673 (41.2) 1,825 (48.0)
Female 1,567 (49.8) 922 (58.8) 2,489 (52.0)
Socio- economic characteristics Household income level High 965 (33.7) 145 (8.3) 1,110 (27.5)
Middle high 755 (29.7) 215 (12.3) 970 (25.5)
Middle low 668 (26.1) 441 (28.3) 1,109 (26.6)
Low 282 (10.5) 763 (51.1) 1,045 (20.3)
Occupation White collar job 546 (22.1) 37 (2.3) 1,139 (29.0)
Blue collar job 1,195 (50.1) 448 (30.5) 2,677 (67.8)
Unemployed 821 (27.8) 945 (67.2) 174 (3.3)
Home ownership Yes 2,078 (69.8) 1,243 (76.6) 3,321 (71.4)
No 628 (30.2) 342 (23.4) 970 (28.6)
Education level ≤Elementary school 540 (18.5) 903 (66.7) 1,443 (29.8)
Middle school 389 (15.2) 188 (13.0) 577 (14.7)
High school 944 (40.0) 219 (13.6) 1,163 (33.8)
College≤ 692 (26.3) 121 (6.7) 813 (21.7)
Medical aid Yes 58 (2.8) 84 (6.0) 142 (3.6)
No 2,649 (97.2) 1,504 (94.0) 4,153 (96.4)
Systemic disease Hypertention Yes 517 (18.1) 792 (55.8) 1,309 (27.0)
No 2,051 (81.9) 654 (44.2) 2,705 (73.0)
Stroke Yes 37 (1.2) 58 (4.1) 95 (1.9)
No 2,531 (98.8) 1,388 (95.9) 3,919 (98.1)
Myocardial infarction, Yes 54 (1.9) 105 (6.4) 159 (3.0)
Angina pectoris No 2,514 (98.1) 1,341 (93.6) 3,855 (97.0)
Diabetes Yes 210 (7.1) 265 (17.8) 475 (9.7)
No 2,358 (92.9) 1,180 (82.2) 3,538 (90.3)
Health behavior High risk drinking No experience 667 (33.1) 424 (58.2) 1,091 (37.2)
Sometimes 672 (34.6) 160 (21.4) 832 (32.4)
Often 499 (32.4) 135 (20.4) 634 (30.4)
Smoking Yes 493 (24.9) 2,071 (75.1) 653 (21.8)
No 160 (11.7) 1,270 (88.3) 3,341 (78.2)
Oral health behavior Oral health screening Yes 716 (27.4) 197 (12.9) 913 (24.0)
No 1,850 (72.6) 1,230 (87.1) 3,080 (76.0)
Brushing frequency ≤1 262 (10.7) 270 (19.0) 532 (12.7)
2 1,033 (39.2) 636 (41.7) 1,669 (39.8)
3≤ 1,320 (50.1) 587 (39.3) 1,907 (47.6)
Number of teeth (M±SE) 25.17±0.40 15.95±0.40 22.88±0.20
Table 2.
The difference between the middle aged and older people remaining teeth (N=4,502)
Variable 40-65 (age)
 65≤ (age)
M±SE t/F M±SE t/F
Gender Male 25.06±0.23 0.87 17.19±0.58 3.65***
Female 25.27±0.14 15.08±0.43
Household income level High 25.84±0.15 6.57*** 18.02±0.94 4.64***
Middle high 25.54±0.45 19.49±1.12
Middle low 24.69±0.29 16.27±1.10
Low 23.23±0.25 14.82±1.11
Occupation White collar job 26.14±0.63 7.20*** 19.97±0.81 3.19***
Blue collar job 24.70±0.66 15.74±0.88
Unemployed 24.95±0.64 16.27±1.98
Home ownership Yes 25.10±0.24 1.16 16.44±0.74 2.36*
No 25.38±0.21 14.66±0.67
Education level ≤Elementary school 23.23±0.30 10.77*** 14.90±0.48 8.13***
Middle school 24.14±0.39 18.40±0.78
High school 25.61±0.3 19.54±0.93
College≤ 26.52±0.32 21.78±0.84
Medical aid Yes 24.51±0.80 0.86 12.51±1.44 2.65**
No 25.20±0.80 16.25±1.41
Hypertention Yes 24.14±0.31 3.81*** 16.01±0.48 1.55
No 25.41±0.33 16.82±0.52
Stroke Yes 22.05±1.03 3.11** 14.97±1.28 1.11
No 25.22±1.01 16.42±1.29
Myocardial infarction, Angina pectoris Yes 21.50±1.24 3.10** 17.07±0.85 0.85
No 25.25±1.21 16.31±0.89
Diabetes Yes 23.60±0.40 4.05*** 15.78±0.77 0.80
No 25.30±0.42 16.48±0.87
High risk drinking No experience 25.47±0.34 1.73 19.35±0.94 1.99*
Sometimes 25.50±0.34 19.32±1.44
Often 24.88±0.28 19.56±0.83
Smoking Yes 24.55±0.31 2.66** 14.36±1.16 1.97
No 25.40±0.32 16.59±1.14
Oral health screening Yes 25.10±0.14 1.48 20.36±0.72 6.45***
No 25.44±0.23 15.72±0.44
Brushing frequency ≤1 23.94±0.45 2.61* 14.82±0.87 0.51
2 23.23±0.45 17.60±0.95
3≤ 25.36±0.47 15.17±0.99

*P<0.05, **P<0.01, ***P<0.001.

Table 3.
Factors associated with the remaining teeth (N=4,502)
Variable 40-64 (age)
 65≤ (age)
B 95% CI B 95% CI
Intercept 16.54 11.28
Household income level (Ref. Low)
High 1.85** 0.76-2.96 2.82* 0.12-5.51
Middle high 1.79** 0.65-2.93 2.84** 0.74-4.95
Middle low 1.27* 0.20-2.34 0.78 ―1.24-2.81
Demographic characteristics Socio- economic characteristics
Gender (Ref. Female)
Male ―0.03 ―0.81-0.28 1.22 ―0.34-2.78
Education level (Ref. ≤Elementary school)
College≤ 2.36*** 1.28-3.44 2.02 ―1.02-5.05
High school 1.51** 0.62-2.41 2.28* 0.05-4.51
Middle school 0.17 ―0.83-1.18 1.48 ―0.35-3033
Occupation (Ref. Unemployed)
White collar ―0.26 ―2.48-1.96 1.08 ―2.67-4.86
Blue collar ―0.12 ―2.28-2.04 0.21 ―3.45-3.88
Home ownership (Ref. Yes)
No 0.47 ―0.08-1.02 ―1.40 ―3.51-0.69
Medical aid (Ref. Yes)
No 0.52 ―3.15-2.11 3.53 ―1.19-8.25
Systemic disease Hypertention (Ref. Yes)
No 0.71 ―0.11-1.54 ―0.03 ―1.57-1.51
Stroke (Ref. Yes)
No 0.16 ―0.97-3.29 0.26 ―3.87-4.39
Myocardial infarction,
Angina pectoris (Ref. Yes)
No 2.96 ―0.29-6.20 ―1.61 ―4.07-0.85
Diabetes (Ref. Yes)
No 1.02 ―0.08-2.13 0.21 ―1.88-2.29
Health behavior High risk drinking (Ref. Often)
No experience 0.17 ―0.49-0.84 ―1.72 ―3.78-0.36
sometimes 0.24 ―0.47-0.95 ―3.08 ―5.79-0.36
Smoking (Ref. Yes)
No 0.81* 0.11-1.50 2.80* 0.25-5.36
Oral health behavior Oral health screening (Ref. Yes)
No ―0.28 ―0.82-0.28 2.82*** 1.26-4.38
Brushing frequency (Ref.=1)
2 0.45 ―0.81-1.53 ―0.16 ―2.93-2.62
3≤ 0.36 ―0.68-1.58 1.05 0.50-4.41
R2 0.094 0.154

Ref.: Reference. *P<0.05, **P<0.01, ***P<0.001.

Table 4.
Interaction analysis of age groups and income levels
Model 1
 Model 2
B B
Age ―5.617 ―0.041*** ―3.408 ―0.212**
House income level ―0.611 ―0.091** ―0.341 ―0.051
Age * House income level ―0.812 ―0.166*
R2 (adj―R2) 0.222 (0.214) 0.225 (0.216)
ΔR2 0.222 0.003
F 25.877*** 24.370***

All related variables controlled. *P<0.05, **P<0.01, ***P<0.001.

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