Table 1 Basic characteristics of the entire respondents in the 2016 and 2019 surveys

Age in years

76.7

(4.8)

77.0

(5.2)

0.20

77.9

(5.5)

77.8

(5.6)

0.38

Married

694

(64.7%)

636

(61.3%)

0.11

553

(36.5%)

557

(36.7%)

0.91

Living alone

380

(35.3%)

410

(38.5%)

0.14

822

(53.8%)

842

(54.7%)

0.66

Years of residence

28.6

(15.7)

28.7

(17.1)

0.86

26.6

(15.5)

28.8

(16.4)

< 0.001

Being employed

321

(30.1%)

332

(31.1%)

0.64

184

(12.2%)

257

(16.4%)

< 0.001

Household income ≥3 million yen

233

(24.3%)

241

(23.7%)

0.79

170

(13.6%)

190

(13.8%)

0.91

Intact cognitive function

996

(91.9%)

947

(88.3%)

0.0060

1433

(93.7%)

1395

(87.9%)

< 0.001

Not depressed (5-item GDS < 2)

569

(56.4%)

548

(56.1%)

0.89

810

(57.7%)

869

(58.8%)

0.57

Number of comorbidities, none

109

(10.1%)

72

(6.7%)

0.011

174

(11.3%)

142

(9.0%)

0.12

 1 comorbidity

271

(25.0%)

242

(22.6%)

396

(25.8%)

381

(24.3%)

 2 comorbidities

278

(25.6%)

271

(25.3%)

349

(22.7%)

390

(24.8%)

 3 comorbidities

189

(17.4%)

215

(20.1%)

255

(16.6%)

260

(16.5%)

 ≥4 comorbidities

237

(21.9%)

271

(25.3%)

361

(23.5%)

398

(25.3%)

Number of impaired IADL items, none

538

(49.3%)

463

(42.4%)

< 0.001

910

(59.0%)

942

(58.7%)

< 0.001

 1 item impaired

305

(28.0%)

289

(26.5%)

361

(23.4%)

314

(19.6%)

 2 items impaired

241

(22.1%)

289

(20.1%)

260

(16.9%)

180

(11.2%)

 3-5 items impaired

7

(0.6%)

120

(11.0%)

11

(0.7%)

169

(10.5%)