Table 1 General characteristics of the participants

Age (years)

 40–49

 50–59

 60–69

 70–79

 ≥ 80

6035 (16.5)

8363 (22.9)

10,500 (28.8)

7114 (19.5)

4476 (12.3)

2862 (16.5)

4004 (23.1)

5286 (30.6)

3339 (19.3)

1811 (10.5)

3173 (16.5)

4359 (22.7)

5214 (27.2)

3775 (19.7)

2665 (13.9)

< 0.001

BMI^a

 Healthy

 Underweight

 Overweight

 Obese

26,006 (71.3)

2767 (7.6)

6707 (18.4)

1008 (2.8)

12,416 (71.8)

871 (5.0)

3628 (21.0)

387 (2.2)

13,590 (70.8)

1896 (9.9)

3079 (16.0)

621 (3.2)

< 0.001

Living status

 With 5 persons or more

 With 3–4 persons

 With 1–2 persons

 Alone

9974 (27.3)

11,509 (31.5)

14,441 (39.6)

564 (1.5)

4799 (27.7)

5363 (31.0)

6842 (39.5)

298 (1.7)

5175 (27.0)

6146 (32.0)

7599 (39.6)

266 (1.4)

0.008

Smoking habit

 Never

 Former smoker

 Current smoker

18,733 (51.3)

10,683 (29.3)

7072 (19.4)

8921 (51.5)

5055 (29.2)

3335 (19.3)

9821 (51.2)

5628 (29.3)

3737 (19.5)

0.812

Drinking habit

 Never

 Former drinker

 Current drinker

12,592 (34.5)

1845 (5.1)

22,051 (60.4)

5988 (34.6)

930 (5.4)

10,384 (60.0)

6604 (34.4)

915 (4.8)

11,667 (60.8)

0.022

History of periodontal disease

 No

 Yes

22,143 (60.7)

14,345 (39.3)

10,024 (57.9)

7278 (42.1)

12,119 (63.2)

7067 (36.8)

Number of remaining teeth

 ≥ 20 teeth

 10–19 teeth

 1–9 teeth

 No natural teeth

 Don’t know

21,925 (60.1)

5306 (14.5)

3356 (9.2)

1583 (4.3)

4318 (11.8)

10,071 (58.2)

2627 (15.2)

1604 (9.3)

761 (4.4)

2239 (12.9)

11,854 (61.8)

2679 (14.0)

1752 (9.1)

822 (4.3)

2079 (10.8)

< 0.001

Bite availability on molars

 Both sides

 One side

 No side

28,859 (79.1)

5510 (15.1)

2119 (5.8)

13,531 (78.2)

2585 (14.9)

1186 (6.9)

15,328 (79.9)

2925 (15.2)

933 (4.9)

< 0.001

History of dry eye diagnosis

 No

 Yes

33,971 (93.1)

2517 (6.9)

16,139 (93.3)

1163 (6.7)

17,832 (92.9)

1354 (7.1)

Feels dryness of eyes

 Never

 Sometimes

 Always

24,845 (68.1)

10,329 (28.3)

1314 (3.6)

11,780 (68.1)

4921 (28.4)

601 (3.5)

13,065 (68.1)

5408 (28.2)

713 (3.7)

0.428

Feels a foreign body in the eyes

 Never

 Sometimes

 Always

26,375 (72.3)

9508 (26.1)

605 (1.7)

12,514 (72.3)

4519 (26.1)

269 (1.6)

13,861 (72.2)

4989 (26.0)

336 (1.8)

0.337