Table 2 Association between dementia and ADL disability among the oldest old in 2001, 2010, and 2018

Dementia (ref = no dementia)

7.29 (6.15–8.64)

< 0.001

7.20 (6.07–8.53)

< 0.001

7.19 (6.05–8.53)

< 0.001

4.59 (3.30–6.39)

< 0.001

Age

1.13 (1.09–1.16)

< 0.001

1.13 (1.10–1.16)

< 0.001

1.13 (1.10–1.17)

< 0.001

1.13 (1.10–1.17)

< 0.001

Gender (ref = male) Female

1.55 (1.25–1.91)

< 0.001

1.53 (1.23–1.89)

< 0.001

1.44 (1.16–1.78)

0.001

1.44 (1.16–1.78)

< 0.001

Study year (ref = 2001)

 2010

0.78 (0.63–0.97)

0.025

0.86 (0.69–1.07)

0.182

0.83 (0.66–1.04)

0.107

0.58 (0.41–0.83)

0.002

 2018

0.66 (0.54–0.81)

< 0.001

0.74 (0.60–0.92)

0.007

0.69 (0.56–0.86)

0.001

0.47 (0.34–0.66)

< 0.001

Occupational class (ref = Non-manual)

 Manual

0.97 (0.81–1.16)

0.741

0.94 (0.79–1.13)

0.505

0.93 (0.78–1.12)

0.463

 Housewives

0.92 (0.66–1.28)

0.630

0.93 (0.66–1.29)

0.649

0.92 (0.66–1.29)

0.642

 Unknown

2.28 (1.67–3.13)

< 0.001

2.28 (1.66–3.14)

< 0.001

2.30 (1.68–3.14)

< 0.000

Number of morbidities 0 (ref)

 1

0.94 (0.70–1.28)

0.698

0.95 (0.70–1.29)

0.739

 2

0.90 (0.67–1.21)

0.496

0.93 (0.69–1.24)

0.611

 3

1.26 (0.93–1.71)

0.135

1.29 (0.95–1.75)

0.103

 ≥ 4

1.85 (1.33–2.56)

< 0.001

1.88 (1.36–2.61)

< 0.001

Dementia * study year (ref = 2001)

 Dementia * 2010

1.80 (1.15–2.83)

0.010

 Dementia * 2018

1.85 (1.21–2.83)

0.005