Oral health disparities among geriatric population according to sexual difference in South Korea: A Nationwide population- based study

DOI: https://doi.org/10.21203/rs.3.rs-1961070/v1

Abstract

The proportion aged 60 years or older in the world's population is expected to double by 2050. In general, they have many complex diseases and poor oral health status. Oral health is one of the important health indicators of elderly people and it is affected by diverse factors, such as socioeconomic status. In this study, gender was considered as an associated factor that is closely related to edentulism. The sexual difference might be more influential within the geriatric population because of lower economic and educational backgrounds in that stage. Edentulism was significantly higher among elderly females than males, when combined with the education level. The lower the level of education, the higher the prevalence of edentulism as much as 24~28 times, especially in female (P=0.002). These findings suggest a more complex relationship between oral health, socioeconomic status, and gender.

Introduction

According to the United Nation’s World Population Prospects 2019, the geriatric population aged 65 years or older is rapidly increasing and is expected to account for 16% of the world's population by 20501. These population experience problems with vision, hearing, and tooth loss with increasing age2 and has at least one restriction in activities of daily living (ADL), such as walking, eating, and washing35. According to the Health and Retirement Study (HRS) in the United States, almost one-fifth of the elderly with these restrictions answered that their health status was poor6. Older females have less access to health care and experience discrimination within the health care system7. In particular, the population from lower socioeconomic backgrounds was more likely to report limitations in daily living8. This makes the geriatric population more dependent on care. Because many complex diseases already existed, they got less attention for their lower priority, and it makes their oral health condition worse9. A decrease in the number of natural teeth makes usual life difficult and health status worse. Intaking of fibrous foods, fruits, and vegetables is decreasing and the risk of gastrointestinal disorders is increasing10,11. Tooth loss usually starts from the age of 40s and rapidly increases when in they were 60s or 70s12. According to the US National Health and Nutrition Examination Survey, edentulism was prevalent in 0.7% of the population aged 20–44 years but increased to 20.2% in the geriatric population aged over 65 years13. In South Korea, the population with no natural teeth was 0.2% when they were in their 40s and reached 13.6% at the age of 70s14.

Tooth loss is affected by various demographic and sociological factors. Studies suggest that the risk factors for edentulism included increasing age15,16, poor oral health practices, disability in function17,18, low socioeconomic status19, and living alone20. Elderly people suffer from health and oral health difficulties and the oral health gap to demographic social factors increasingly added and affects their overall life21. There are differences by sex in tooth loss as well, more frequently happening in females22. Supa et al mentioned that among males the major factor affecting edentulism was smoking; however, among females, it was lower socioeconomic status23. The elderly female showed a fifteen times higher economic dependence than males24 and these exacerbate oral health conditions and increase dissatisfaction, depression25, or inconvenience in their daily life of them26. Sexual differences in health among the elderly have been widely reported2729 but they are not normally considered to be related to disparities, especially in oral health. There is a limited number of studies available to establish the relationship between the diverse variables related to these differences.

This study aimed to understand oral health disparities in the geriatric population, considering sexual difference as a related factor, through analysis of data obtained from the Korean National Health and Nutrition Survey (KNHANES Ⅶ, 2016 to 2018); our findings will aid in the proper planning and implementation of oral health policies.

Results

1. General characteristics of the study population:

The total number of participants aged 65 years and older in the 7th National Health and Nutrition Survey (2016–2018) was 3,426. Among these elderly participants, 57.6% were female, which was 15% higher than the proportion of than male (Table 1). Most participants had only elementary school education or none (57.6%). Female had a graduation rate for elementary school, that was 1.5 times the graduation rate of male; however, the number of females graduating high school was only 0.5 times the number of male graduating high school. Twenty-one percent of the participants lived alone; twice as many females lived alone than male. With respect to morbidities, the proportion of the elderly population with hypertension and diabetes was 62.3% and 25.7%, respectively. Female showed a 5% higher rate of hypertension than male, but there was no significant difference in the prevalence of diabetes. The rate of drinking more than once a month was 34.4% and male were a three times higher rate than female. With respect to smoking, 15 times as many males reported a history of smoking than female. Almost 70% of subjects were involved in physical activity on a weekly basis with male reporting a higher likelihood of engaging in physical activity than female. Most people brushed more than twice a day (76.0%); 10% more female brushed more than twice a day than male. Only a quarter of the participants did an annual oral examination; more male received the examination than female.

2. Prevalence of edentulism in elderly individuals

The proportion of the geriatric population without teeth was 9.5%. This increased with age, with 18.1% of participants aged 80 years being edentulous; female showed a higher rate of edentulism than male (Table 2). With respect to educational level, the prevalence of edentulism was 11.1% in people finished elementary school, which was twice as high as that among high school graduates and those with a higher education. The difference of prevalence of edentulism by education level was 10 times higher in female than in male. The higher the income, the lower the prevalence of edentulism, especially in female; the gap between the first and fifth quartiles was almost double compared to male. The participants who lived alone had a slightly higher prevalence of edentulism than participants who lived with someone else. There was no statistical difference among participants with hypertension in general. However, female with this metabolic disease had a higher prevalence of edentulism. The participants who did not have a history of drinking monthly had a higher prevalence of edentulism, but there was no difference according to gender. The percent of the people with no teeth was 11.4% in smokers, which was higher than that in non-smokers, as much as twice in both male and female. In the case of physical activity, male who were not engaged in physical activity had a higher rate of edentulism. Participants, both male and female, who brushed lesser than twice a day had a five times higher likelihood of edentulism than those who brushed more. The rate of edentulism was almost five times higher in participants who did not receive oral examinations once a year; the gap was bigger in male, as ten times more likely to be edentulous.

3. Logistic regressions by risk factors associated with edentulism in elderly individuals

The logistic regression analysis for the factors affecting the prevalence of edentulism among elderly individuals is presented in Table 3. Age, educational level, income, living alone, and lifetime smoking were significantly associated with edentulism among elderly individuals. Participants who brushed fewer than twice a day were five times more likely to be edentulous than participants who did, and participants who did not receive yearly oral examinations were six times more likely to be edentulous than participants who did. After adjustment for all risk factors, the geriatric population who did not receive yearly oral examinations showed a lower odds ratio: almost four times that before. The coefficient of determination of NagelKerke R2 in this model was 0.185. In the third model considering the interaction between gender and education level, the odds ratio of edentulism decreased for females with the opposite results of those from the second model. Compared to the group of elderly female participants who graduated high school, people who finished middle school showed 29 times higher risk of being edentulous, and people who graduated elementary school were at a 24-fold higher risk of being edentulous. The lower the level of education, the higher the prevalence of edentulism, especially in females. The coefficient of determination of NagelKerke R2 in the final model was 0.198.

 
Table 1

Characteristics of the study population of elderly between 2016 to 2018

 

Variables

Total

Male

Female

p

N

%

n

%

n

%

Total

3,426

100.0

1,465

42.4

1,961

57.6

 
 

Age

 

65–69

1,059

31.5

482

33.0

577

30.4

0.483

 

70–74

916

27.4

387

27.4

529

27.4

 

75–79

830

23.7

350

22.5

480

24.6

 

≥ 80

621

17.4

246

17.1

375

17.6

 

Educational level

 

High school and more

834

27.1

557

41.6

277

16.6

< 0.001

 

Middle school

476

15.3

248

18.6

228

12.8

 

Elementary school

1,906

57.6

570

39.8

1,336

70.6

 

Missing value

210

 

90

 

120

 
 

Household income quintile

 

1st

700

21.1

300

20.9

400

21.3

0.944

 

2nd

692

19.3

297

19.9

395

18.8

 

3rd

697

19.7

296

19.6

401

19.8

 

4th

673

20.4

286

20.4

387

20.4

 

5th

644

19.5

277

19.2

367

19.8

 

Missing value

20

 

9

 

11

 
 

Living status

 

Alone

853

21.0

201

11.7

652

27.8

< 0.001

 

With family

2,573

79.0

1,264

88.3

1,309

72.2

 

Location of residence

 

Province

1,852

53.8

762

52.5

1,090

54.7

0.203

 

Metropolitan

1,574

46.2

703

47.5

871

45.3

 

Hypertension

 

Yes

2,172

62.3

879

59.4

1,293

64.5

0.010

 

No

1,248

37.7

585

40.6

663

35.5

 

Missing value

6

 

1

 

5

 
 

Diabetes

 

Yes

824

25.7

377

26.8

447

24.8

0.288

 

No

2,239

74.3

955

73.2

1,284

75.2

 

Missing value

363

 

133

 

230

 
 

Drinking per month

 

Once and more

1,144

34.4

813

56.6

331

17.8

< 0.001

 

Never

2,222

65.6

636

43.4

1,586

82.2

 

Missing value

60

 

16

 

44

 
 

Lifetime smoking

 

Experienced

1,216

35.8

1,116

77.0

100

5.1

< 0.001

 

Never

2,146

64.2

330

23.0

1,816

94.9

 

Missing value

64

 

19

 

45

 
 

Aerobic physical activity*

 

No

2,268

69.0

904

64.1

1,364

72.7

< 0.001

 

Yes

942

31.0

472

35.9

470

27.3

 

Missing value

216

 

89

 

127

 
 

Tooth brushing per day

 

Less than twice

840

24.0

449

30.3

391

19.4

< 0.001

 

Twice and more

2,586

76.0

1,016

69.7

1,570

80.6

 

Oral exam in last year

 

No

2,567

75.5

1,053

72.1

1,514

78.1

< 0.001

 

Yes

795

24.5

393

27.9

402

21.9

 

Missing value

64

 

19

 

45

 
*Medium-intensity physical activity for more than 2 hours and 30 minutes, high-intensity physical activity for more than 1 hour and 15 minutes, or mixed intensity per week (1 minute of high-intensity physical activity is equal for 2 minutes of medium-intensity).

 
Table 2

Prevalence of edentulism according to characteristics of the study population of elderly between 2016 to 2018

Variables

Total

Male

Female

N

n

%

p

N

n

%

p

N

n

%

p

Total

3,426

328

9.5

0.597

1,465

138

9.1

 

1,961

190

9.8

 

Age

 

65–69

1,059

40

3.9

< 0.001

482

23

4.7

< 0.001

577

17

3.2

< 0.001

 

70–74

916

64

7.4

387

36

8.8

529

28

6.3

 

75–79

830

110

13.1

350

43

12.7

480

67

13.3

 

≥ 80

621

114

18.1

246

36

13.5

375

78

21.4

Educational level

 

High school and more

834

49

5.1

< 0.001

557

44

7.2

0.126

277

5

1.2

< 0.001

 

Middle school

476

33

6.8

248

21

8.2

228

12

5.2

 

Elementary school

1,906

208

11.1

570

64

11.2

1,336

144

11.0

Household income quintile

 

1st

700

84

11.1

0.007

300

34

9.4

0.417

400

50

12.3

0.008

 

2nd

692

77

11.8

297

33

11.7

395

44

11.9

 

3rd

697

71

11.0

396

28

9.6

401

43

12.0

 

4th

673

51

7.5

286

25

8.7

387

26

6.6

 

5th

644

42

6.1

277

18

6.4

367

24

5.9

Living status

 

Alone

853

117

13.9

< 0.001

201

31

16.2

0.001

652

86

13.2

0.009

 

With family

2,573

211

8.3

1,264

107

8.2

1,309

106

8.4

Location of residence

 

Province

1,852

190

10.5

0.111

762

80

10.3

0.110

1,090

110

10.7

0.328

 

Metropolitan

1,574

138

8.3

703

58

7.8

871

80

8.7

High blood pressure

 

Yes

2,172

212

9.8

0.324

879

75

7.8

0.065

1,293

137

11.1

0.004

 

No

1,248

113

8.8

585

63

11

663

50

6.9

Diabetes

 

Yes

824

85

9.9

0.171

377

38

8.9

0.751

447

47

10.6

0.153

 

No

2,239

183

8.0

955

82

8.3

1,294

101

7.7

Drinking per month

 

Once and more

1,144

89

7.7

0.044

813

64

8.0

0.106

331

25

7.0

0.124

 

Never

2,222

224

10.0

636

73

10.7

1,586

151

9.7

Lifetime smoking

 

Experienced

1,216

139

11.4

0.008

1,116

123

10.7

< 0.001

100

16

19.5

0.008

 

Never

2,146

174

8.0

330

14

4.1

1,816

160

8.7

Aerobic physical activity*

 

No

2,268

224

9.8

0.105

904

89

10.4

0.011

1,364

135

9.4

0.479

 

Yes

942

68

6.8

472

39

6.1

470

29

7.4

Tooth brushing per day

 

Less than twice

840

181

21.7

< 0.001

449

85

19.2

< 0.001

391

96

24.6

< 0.001

 

Twice and more

2,586

147

5.6

1,016

53

4.7

1,570

64

6.2

Oral exam last year

 

No

2,567

295

11.6

< 0.001

1,053

130

12.2

< 0.001

1,514

165

11.1

< 0.001

 

Yes

795

18

2.1

393

7

1.3

402

11

2.7

*Medium-intensity physical activity for more than 2 hours and 30 minutes, high-intensity physical activity for more than 1 hour and 15 minutes, or mixed intensity per week (1 minute of high-intensity physical activity is equal for 2 minutes of medium-intensity).

 
Table 3

Odds ratio (OR) and 95% confidence interval (CI) estimated from logistic regression model for edentulism of elderly between 2016 to 2018

Variables

No-interaction

Interaction (Sex*Educational Level)

Unadjusted

Model 1

Model 2

OR

95% CI

p

OR

95% CI

p

OR

95% CI

p

Sex (= Male)

     
 

Female

1.079

0.813–1.433

0.597

1.507

0.740–3.071

0.258

0.074

0.010–0.576

0.013

Age (= 65–69)

     
 

70–74

1.977

1.211–3.229

0.007

2.049

1.225–3.428

0.006

2.130

1.269–3.576

0.004

 

75–79

3.745

2.300-5.393

< 0.001

3.571

2.053–6.210

< 0.001

3.486

1.999–6.080

< 0.001

 

≥ 80

5.507

3.619–8.378

< 0.001

3.382

1.967–5.816

< 0.001

3.325

1.935–5.713

< 0.001

Educational level (= High school and more)

     
 

Middle school

1.364

0.817–2.276

0.234

1.440

0.809–2.563

0.215

0.908

0.465–1.773

0.777

 

Elementary school

2.337

1.592–3.430

< 0.001

1.453

0.901–2.342

0.125

0.936

0.524–1.673

0.824

Household income (= 5th)

     
 

4th

1.249

0.766–2.037

0.371

1.168

0.660–2.065

0.594

1.121

0.634–1.981

0.694

 

3rd

1.914

1.148–3.191

0.013

1.247

0.631–2.462

0.525

1.198

0.613–2.342

0.598

 

2nd

2.074

1.310–3.283

0.002

1.036

0.561–1.914

0.909

1.015

0.554–1.859

0.961

 

1st

1.935

1.222–3.064

0.005

0.880

0.437–1.711

0.719

0.852

0.428–1.697

0.649

Living status (= With family)

     
 

Alone

1.791

1.332–2.407

< 0.001

1.502

0.936–2.409

0.092

1.508

0.936–2.432

0.091

Location of residence (= Metropolitan )

     
 

Province

1.304

0.940–1.808

0.111

1.202

0.825–1.751

0.336

1.227

0.841–1.790

0.288

High blood pressure (= No)

     
 

Yes

1.133

0.884–1.453

0.324

0.858

0.638–1.153

0.310

0.875

0.651–1.175

0.373

Diabetes (= No)

     
 

Yes

1.259

0.905–1.751

0.172

1.008

0.705–1.441

0.966

1.006

0.706–1.433

0.976

Drinking per month (= Never)

     
 

Once and more

0.749

0.565–0.992

0.749

0.854

0.526–1.081

0.124

0.748

0.523–1.071

0.113

Lifetime smoking (= Never)

     
 

Experienced

1.481

1.139–1.927

0.003

2.403

1.295–4.460

0.006

2.346

1.268–4.341

0.007

Aerobic physical activity* (= Yes)

     
 

No

1.483

0.919–2.393

0.107

0.922

0.563–1.509

0.746

0.920

0.562–1.506

0.739

Tooth brushing per day (= Twice and more)

     
 

Less than twice

4.672

3.501–6.235

< 0.001

3.471

2.502–4.815

< 0.001

3.548

2.559–4.919

< 0.001

Oral exam in last year (= Yes)

     
 

No

6.222

3.657–10.586

< 0.001

3.807

2.071–6.995

< 0.001

3.743

2.040–6.868

< 0.001

Gender*educational level (= Female*high school and more)

     
 

Female*middle school

           

28.877

3.488–238.080

0.002

 

Female*elementary school

           

24.422

3.272-182.275

0.002

NagelKerke R2

 

0.185

0.198

*Model 1: fully adjusted for gender, age group, educational level, household income quintile, living status with family, location of residence, existence of high blood pressure or diabetes, drinking, smoking, physical activity, frequency of tooth brushing, and oral exam experience in last year, Model 2: Model 1 plus interaction between gender and educational level

Discussion

The proportion of the world's population aged 60 years or older is expected to double by 2050. As a result, population aging is recognized as an important problem worldwide30. Oral health is an essential health indicator among elderly people9,10. A gap is reported in the oral health of geriatrics for various factors including socioeconomic and behavioral factors. In this study, gender was considered the main factor that affected the prevalence of edentulism among those aged 65 years or above.

There was no difference in the prevalence of edentulism according to gender until the interaction between gender and education level was considered, which was significant. Edentulism among elderly females was significantly higher than that among males when categorized by education level. The prevalence of edentulism among middle school or elementary school graduates and participants with lower education levels was 24–28 times that of high school graduates or participants with higher education in an elderly female. The prevalence of edentulism among elderly individuals in South Korea was 9.5%, which was lower than the prevalence of 12.9% observed in the United States31, but higher than the prevalence of 8.1% observed in Japan32. The proportion of elderly individuals is expected to reach 46.5% in 206733, of which the proportion of female elderly individuals is expected to be about 55%, higher than that of male elderly individuals in Korea. Gender may be an important factor associated with edentulism among the geriatric population, especially for economic and educational backgrounds. Some studies have reported that the lower the education or income, the higher the prevalence of edentulism3437. This population is also reported to have lower subjective oral health, which might affect care for oral health38. Most of them showed a lower tendency to visit dental clinics39, which might have worsened oral health conditions. There was a significant difference in edentulism by socioeconomic level in an elderly female. This is the reason that the interaction between gender and socioeconomic factors is assumed to exist. There might be a more complex relationship between oral health, socioeconomic status, and gender. Among the geriatric Korean population, a female had a significantly less chance than a male of being educated. They also lived longer than males and many of them lived alone40. Elderly females were found to be more sensitive to socio-economic factors as well. The gap in economic poverty appeared in poorer elderly females, which worsened oral health41. Paola et al reported that elderly females did more preventive oral care than males, but complex mechanisms working in oral health make necessary careful management42. The oral health gender gap should be considered not just gender itself but also the contextual mechanism around it.

Regular tooth brushing twice a day and yearly oral examination was found to have effects on edentulism. Healthy behaviors were reported as closely related to oral health43. The prevalence of edentulism was higher in participants with a history of smoking, brushing fewer than twice a day, and not taking yearly oral examinations44,45. These oral health behaviors showed different patterns depending on gender, and females are known to visit the dentist more frequently, perform better oral care46, and have better knowledge, attitude, and behavior about oral health than male47,48. The elderly female showed about a 10% higher rate of brushing their teeth twice or more a day than males in this study. Likewise, each gender in elderly individuals had significant associations with different oral health behavior factors, such as physical activity for males and hypertension for females. The type of residence also showed a significant association. Elderly individuals living alone were at an almost two times higher risk of edentulism. Kim et al reported that elderly people who lived alone had a higher possibility of needing dentures and experiencing difficulty in mastication than geriatric people living with their families49. Elderly males living without families showed a higher level of edentulism. Elderly individuals living alone might have fewer opportunities to acquire and exchange information about oral health and more difficulties in practicing healthy oral behavior50.

There are several limitations of this study. First, social relationships and support might influence physical, mental, and oral health and behavior, especially in geriatric people51,52. The data used in this study did not include social capital variables such as the number of friends and meetings. It is necessary to understand the social relationship of elderly individuals with oral health in depth in the future. Second, it is difficult to identify the causal relationship because the data as this was a cross-sectional study. The present education or income levels were surveyed but the past socioeconomic status or oral health behavior of the participant could not be included in this survey. The causal relationship from previous conditions would be important in the study of the geriatric population. Future studies must design a longitudinal data set such as a cohort framework to identify the influential relationship after identifying the related factors. Even with these limitations, this study established the fundamentally important health characteristics of an aging society according to gender with oral health status using national representative data.

Conclusion

This study revealed the association between gender and socioeconomic factors related to the oral health of elderly individuals. In edentulism in elderly individuals, there was no difference according to gender, initially. After considering the interaction between gender and education, an elderly female had a lower possibility of being edentulous than a male. The prevalence of edentulism in the elderly female who graduated middle school or elementary school was 24 ~ 28 times that of high school graduates. Each gender of the geriatric population had significant associations with different oral health behavior factors, such as physical activity for males and hypertension for females. In conclusion, in the plan for oral health improvement in elderly individuals, gender characteristics must be identified, such as socioeconomic factors for females and health behavior factors for males.

Methods

Study Subjects. This study analyzed oral health conditions by gender in the geriatric population aged 65 years or older using the Korean National Health and Nutrition Survey (KNHANES Ⅶ, 2016-2018) data. The sampling frame was layered based on the size of the area (cities, provinces, and districts) and housing types (general housing, apartments). The ratio of residential area and educational background of household owners was used as the intrinsic stratification criteria. Finally, 576 districts were surveyed over 3 years, with 10,611 households participating in the study. A cohort of 24,269 participants was recruited with a response rate of 76.6%. Among them, 3,426 people were elderly, which was 21.0% of all subjects.

Study Variable. The general characteristics of the study sample were gender, age, education or income level, household type, region, comorbidities such as hypertension or diabetes, health-related behavior such as drinking, smoking, aerobic physical activity, brushing teeth, or visiting a dental clinic for oral examination per year. The independent variables are classified as shown in Table 1. The type of household was categorized by the number of family members - one as living alone and two or more as family living together. A person involved in as much as medium intensity physical activity for 2 h and 30 min, high-intensity physical activity for 1 h and 15 min, or medium and high-intensity physical activity per week (1-min-high intensity for 2 min) was defined as properly engaging in physical activity.

Statistical Analysis: A complex sample analysis was used because the KNHANES was a two-stage stratified cluster sampling. It was conducted by generating an integrated weight based on the prepared analysis plan file. The plan file adapted analysis weight with “oral examination weight”, design of the strata with “variance estimation” and “group aged 65 years or above, and cluster as primary sampling unit with the district. Complex sample frequency and chi-square tests were conducted to find out the difference in the prevalence of edentulism according to socioeconomic factors, chronic diseases, and health-related behaviors. A complex sample logistical regressions were performed with an unadjusted model with univariate variables, a fully adjusted model including all variables (Model 1), and an advanced model with interaction by gender and education (Model 2). All analyses used SPSS (Statistical Packages for Social Science 26.0. SPSS Inc., USA) and statistical significance was set to α=0.05.

Ethical approval and informed consent

This study used the dataset obtained from the KNHANES Ⅶ, 2016 to 2018. All KNHANES were conducted with participants’ informed consent after approval by the Research Ethics Review Committee of the Korea Disease Control and Prevention Agency (KDCA) (IRB No. 2018-03-P-A for the KNHANES VII). This analytical study was approved again by the institutional review board (IRB) of Kyung Hee University (IRB No. KHSIRB-21-337(EA)) as exemption of the review because this retrospective analysis included the dataset of national surveillance and did not contain personally identifiable information. All methods were carried out following the KNHANES analytic guidelines and regulations.

Data availability

The data that supports the findings of this study is available from the KDCA, but restrictions apply to the availability of data, which was used with permission for the current study and therefore not publicly available. Data is however available upon reasonable request and with permission of KDCA.

Declarations

Acknowledgements:

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1F1A1063105).

Author Contributions

H.A.P. and J.I.R contributed for the conception and design of the work and wrote the main manuscript text; S.H.S has substantial contributions to the acquisition, analysis, and interpretation of data. All authors reviewed the manuscript.

Competing Interests:

The authors declare no competing interests.

Additional information

Correspondence and requests for materials should be addressed to J.I.R

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