Table 1 Descriptive characteristics of the study subjects

Gender

 Male

3,563

48.4

201

37.3

3,764

47.6

p < 0.001

 Female

3,803

51.6

338

62.7

4,141

52.4

Age

 65–74 years (younger elderly)

4,411

59.9

162

30.1

4,573

57.8

p < 0.001

 ≥75 years (older elderly)

2,955

40.1

377

69.9

3,332

42.2

BADL score 2001

 0

4

0.1

29

5.4

33

0.4

p < 0.001

 1

5

0.1

19

3.5

24

0.3

 2

578

7.8

95

17.6

673

8.5

 3

6,618

89.8

374

69.4

6,992

88.5

 Missing

161

2.2

22

4.1

183

2.3

IADL score 2001

 0

21

0.3

64

11.9

85

1.1

p < 0.001

 1

36

0.5

57

10.6

93

1.2

 2

55

0.7

55

10.2

110

1.4

 3

115

1.6

41

7.6

156

2.0

 4

547

7.4

65

12.1

612

7.7

 5

6,419

87.1

216

40.1

6,635

83.9

 Missing

173

2.3

41

7.6

214

2.7

Frequency of going outside 2001

 <Once a month

203

2.8

92

17.1

295

3.7

p < 0.001

 >Once a month

451

6.1

83

15.4

534

6.8

 >3–4 times a week

6,408

87.0

309

57.3

6,717

85.0

 Missing

304

4.1

55

10.2

359

4.5

BADL score 2004

 0

5

0.1

82

15.2

87

1.1

p < 0.001

 1

29

0.4

112

20.8

141

1.8

 2

810

11.0

193

35.8

1,003

12.7

 3

6,110

82.9

90

16.7

6,200

78.4

 Missing

412

5.6

62

11.5

474

6.0

IADL score 2004

 0

35

0.5

120

22.3

155

2.0

p < 0.001

 1

48

0.7

93

17.3

141

1.8

 2

74

1.0

63

11.7

137

1.7

 3

188

2.6

41

7.6

229

2.9

 4

624

8.5

44

8.2

668

8.5

 5

5,922

80.4

93

17.3

6,015

76.1

 Missing

475

6.4

85

15.8

560

7.1

Frequency of going outside 2004

 <Once a month

88

1.2

68

12.6

156

2.0

p < 0.001

 >Once a month

1,055

14.3

186

34.5

1,241

15.7

 >3–4 times a week

5,870

79.7

205

38.0

6,075

76.9

 Missing

353

4.8

80

14.8

433

5.5

Educational level 2001

 Graduation from junior high school

2,580

35.0

268

49.7

2,848

36.0

p < 0.001

 Graduation from high school

2,644

35.9

123

22.8

2,767

35.0

 Graduation from junior college or higher

1,621

22.0

87

16.1

1,708

21.6

 Missing

521

7.1

61

11.3

582

7.4

Annual income 2001

 <$13,000

419

5.7

58

10.8

477

6.0

p < 0.001

 <$39,000

2,520

34.2

230

42.7

2,750

34.8

 <$91,000

2,991

40.6

140

26.0

3,131

39.6

 >$91,000

582

7.9

23

4.3

605

7.7

 Missing

854

11.6

88

16.3

942

11.9