Table 1 Baseline characteristics of independent older adults aged ≥ 65 years with or without influenza or hospitalization due to influenza at the follow-up survey
|  | Influenza (n = 76,731) a | Hospitalization due to influenza (n = 76,734) a | |||||||
|---|---|---|---|---|---|---|---|---|---|
No (n = 72,096, 94.0%) | Yes (n = 4635, 6.0%) | No (n = 76,560, 99.8%) | Yes (n = 174, 0.2%) | ||||||
n | % | n | % | n | % | n | % | ||
Frailty | Nonfrail | 36,913 | 51.2 | 2220 | 47.9 | 39,046 | 51.0 | 50 | 29.0 |
Prefrail | 31,001 | 43.0 | 2104 | 45.4 | 32,997 | 43.1 | 100 | 57.4 | |
Frail | 4182 | 5.8 | 311 | 6.7 | 4517 | 5.9 | 24 | 13.6 | |
Age group | 65‒74 | 44,339 | 61.5 | 3022 | 65.2 | 47,314 | 61.8 | 61 | 35.1 |
 ≥ 75 | 27,757 | 38.5 | 1613 | 34.8 | 29,246 | 38.2 | 113 | 64.9 | |
Sex | Male | 34,318 | 47.6 | 2188 | 47.2 | 36,366 | 47.5 | 108 | 62.1 |
Female | 37,778 | 52.4 | 2447 | 52.8 | 40,194 | 52.5 | 66 | 37.9 | |
Educational attainment (years) |  < 6 | 433 | 0.6 | 19 | 0.4 | 459 | 0.6 | 3 | 1.8 |
6–9 | 19,250 | 26.7 | 1154 | 24.9 | 20,365 | 26.6 | 56 | 32.0 | |
10–12 | 30,929 | 42.9 | 1975 | 42.6 | 32,844 | 42.9 | 69 | 39.9 | |
 ≥ 13 | 21,052 | 29.2 | 1465 | 31.6 | 22,509 | 29.4 | 43 | 24.9 | |
Others | 360 | 0.5 | 23 | 0.5 | 383 | 0.5 | 2 | 1.3 | |
Equivalized income, million yen |  < 0.5 | 5984 | 8.3 | 357 | 7.7 | 6278 | 8.2 | 18 | 10.3 |
0.50–0.99 | 20,908 | 29.0 | 1298 | 28.0 | 22,126 | 28.9 | 55 | 31.6 | |
1.00–1.99 | 14,996 | 20.8 | 1052 | 22.7 | 16,001 | 20.9 | 30 | 17.2 | |
2.00–3.99 | 9949 | 13.8 | 663 | 14.3 | 10,565 | 13.8 | 17 | 9.8 | |
 ≥ 4.00 | 20,259 | 28.1 | 1265 | 27.3 | 21,513 | 28.1 | 54 | 31.0 | |
Marital status | Married | 54,505 | 75.6 | 3652 | 78.8 | 58,032 | 75.8 | 134 | 77.0 |
Widowed | 12,328 | 17.1 | 663 | 14.3 | 12,939 | 16.9 | 26 | 14.9 | |
Divorced | 3100 | 4.3 | 199 | 4.3 | 3292 | 4.3 | 9 | 5.2 | |
Never married | 2091 | 2.9 | 116 | 2.5 | 2220 | 2.9 | 5 | 2.9 | |
Other | 72 | 0.1 | 5 | 0.1 | 77 | 0.1 | - | - | |
Household structure (Living with who or by alone) | Spouse | 33,597 | 46.6 | 2211 | 47.7 | 35,677 | 46.6 | 79 | 45.4 |
Alone | 6777 | 9.4 | 357 | 7.7 | 7120 | 9.3 | 17 | 9.8 | |
Offspring | 4758 | 6.6 | 246 | 5.3 | 4976 | 6.5 | 9 | 5.2 | |
Spouse and offspring | 10,814 | 15.0 | 723 | 15.6 | 11,484 | 15.0 | 22 | 12.6 | |
Three-generation household | 7065 | 9.8 | 514 | 11.1 | 7579 | 9.9 | 27 | 15.5 | |
The other households other than above | 9084 | 12.6 | 584 | 12.6 | 9647 | 12.6 | 20 | 11.5 | |
Smoking status | Smoke almost everyday | 6272 | 8.7 | 375 | 8.1 | 6584 | 8.6 | 19 | 10.9 |
Smoke sometimes | 1009 | 1.4 | 70 | 1.5 | 1072 | 1.4 | 5 | 2.9 | |
Quit smoking < 5 years ago | 2379 | 3.3 | 134 | 2.9 | 2526 | 3.3 | 10 | 6.0 | |
Quit smoking ≥ 5 years ago | 19,538 | 27.1 | 1298 | 28.0 | 20,824 | 27.2 | 53 | 30.4 | |
Never smoked | 42,897 | 59.5 | 2753 | 59.4 | 45,553 | 59.5 | 87 | 49.8 | |
High-risk disease | No | 53,207 | 73.8 | 3370 | 72.7 | 56,425 | 73.7 | 108 | 61.8 |
1 or more | 18,889 | 26.2 | 1265 | 27.3 | 20,135 | 26.3 | 66 | 38.2 | |
Influenza vaccination | No | 29,559 | 41.0 | 1664 | 35.9 | 31,236 | 40.8 | 49 | 28.4 |
Yes | 42,537 | 59.0 | 2971 | 64.1 | 45,324 | 59.2 | 125 | 71.6 | |
Civic participation | No participation | 41,095 | 57.0 | 2443 | 52.7 | 43,410 | 56.7 | 108 | 62.2 |
1 or more | 31,001 | 43.0 | 2192 | 47.3 | 33,150 | 43.3 | 66 | 37.8 | |
Reciprocity | No reciprocity | 2019 | 2.8 | 102 | 2.2 | 2067 | 2.7 | 8 | 4.7 |
1 or more | 70,077 | 97.2 | 4533 | 97.8 | 74,493 | 97.3 | 166 | 95.3 | |
Number of friends met in the last month | 0 | 5407 | 7.5 | 287 | 6.2 | 5665 | 7.4 | 17 | 9.5 |
1–2 | 12,184 | 16.9 | 714 | 15.4 | 12,862 | 16.8 | 39 | 22.3 | |
3–5 | 17,375 | 24.1 | 1089 | 23.5 | 18,451 | 24.1 | 45 | 25.9 | |
6–9 | 10,310 | 14.3 | 667 | 14.4 | 11,025 | 14.4 | 21 | 11.9 | |
10 or more | 26,748 | 37.1 | 1877 | 40.5 | 28,557 | 37.3 | 53 | 30.3 | |