Introduction
Methods
Study design and data sources
We used the CRIS resource [24] to identify dementia cases for our cohort. It provides research access to anonymised electronic medical records from SLaM, which provides mental healthcare including dementia assessment and management [25] for a London, UK, catchment area containing 1.2 million residents. CRIS enables anonymised data extraction from structured record fields, and unstructured text data using natural language processing algorithms [24, 26] developed using General Architecture for Text Engineering (GATE) software [27].The South London and Maudsley (SLaM) National Health Service (NHS) Foundation Trust Case Register “Clinical Record Interactive Search” (CRIS) data extraction tool.
NHS Digital Hospital Episode Statistics (HES).
Study participants
Covariates
Statistical analysis
Cumulative incidence and admission rate of hospitalisation
Age-standardised admission ratio for dementia
Association of sociodemographic and clinical factors with hospitalisation
Results
Characteristic | All people with dementia (n = 10,137) | Admitted to hospital (n = 7693) | Not admitted to hospital (n = 2444) | Significance testa | ||||
---|---|---|---|---|---|---|---|---|
n | % | n |
%
| n | % | |||
Age at diagnosis | Mean (SD) | 82.1 (7.2) | 82.1 (7.0) | 81.8 (7.7) | t = − 2.3, p = 0.02 | |||
65–69 | 600 | 5.9 | 412 | 5.4 | 188 | 7.7 | χ2 = 47.4, p < 0.001 | |
70–74 | 1203 | 11.9 | 866 | 11.3 | 337 | 13.8 | ||
75–79 | 1998 | 19.7 | 1541 | 20.0 | 457 | 18.7 | ||
80–84 | 2602 | 25.7 | 2044 | 26.6 | 558 | 22.8 | ||
85–89 | 2446 | 24.1 | 1890 | 24.6 | 556 | 22.8 | ||
90 + | 1288 | 12.7 | 940 | 12.2 | 348 | 14.2 | ||
Missing | 0 | 0 | 0 | |||||
Sex | Female | 6262 | 61.8 | 4662 | 60.6 | 1600 | 65.5 | χ2 = 18.5, p < 0.001 |
Missing | 1 | 1 | 0 | |||||
Ethnicity | White | 7640 | 77.3 | 5915 | 78.4 | 1725 | 73.8 | χ2 = 28.9, p < 0.001 |
Asian | 453 | 4.6 | 345 | 4.6 | 108 | 4.6 | ||
African/Caribbean | 1445 | 14.6 | 1050 | 13.9 | 395 | 16.9 | ||
Other | 344 | 3.5 | 234 | 3.1 | 110 | 4.7 | ||
Missing | 255 | 149 | 106 | |||||
Marital statusb | Married | 3202 | 33.5 | 2454 | 33.5 | 748 | 33.4 | χ2 = 4.5, p = 0.21 |
Divorced | 769 | 8.0 | 590 | 8.1 | 179 | 8.0 | ||
Widowed | 3892 | 40.7 | 3007 | 41.1 | 885 | 39.5 | ||
Single | 1701 | 17.8 | 1270 | 17.4 | 431 | 19.2 | ||
Missing | 573 | 372 | 201 | |||||
Mean deprivation scoreb (SD) | 27. 2 (11.1) | 27.3 (11.1) | 26.7 (11.1) | t = − 2.14, p = 0.03 | ||||
Missing | 40 | 22 | 18 | |||||
Mean MMSEb (SD) | 18.6 (6.3) | 18.6 (6.2) | 18.6 (6.5) | t = − 0.17, p = 0.87 | ||||
Missing | 1579 | 1049 | 530 | |||||
Problemb with: (from HoNOS subscale) | Agitation | 1998 | 20.7 | 1494 | 20.2 | 504 | 22.2 | χ2 = 4.3, p = 0.04 |
Self-injury | 136 | 1.4 | 108 | 1.5 | 28 | 1.2 | χ2 = 0.65, p = 0.42 | |
Alcohol/drugs | 302 | 3.1 | 233 | 3.2 | 69 | 3.0 | χ2 = 0.07, p = 0.79 | |
Physical illness | 5511 | 57.1 | 4307 | 58.3 | 1204 | 53.1 | χ2 = 18.9, p < 0.001 | |
Hallucinations | 1354 | 14.1 | 1058 | 14.4 | 296 | 13.1 | χ2 = 2.2, p = 0.14 | |
Depressed mood | 1416 | 14.7 | 1083 | 14.7 | 333 | 14.7 | χ2 = 0.002, p = 0.96 | |
Daily living | 5981 | 62.1 | 4601 | 62.5 | 1380 | 61.0 | χ2 = 1.75, p = 0.19 | |
Living conditions | 1220 | 12.8 | 952 | 13.1 | 268 | 11.9 | χ2 = 1.9, p = 0.17 | |
Missingc | 513 | 452 | 315 | |||||
Last recorded dementia diagnosis | Alzheimer’s disease | 5166 | 51.0 | 3884 | 50.5 | 1282 | 52.5 | χ2 = 13.8, p = 0.008 |
Vascular dementia | 2223 | 21.9 | 1741 | 22.6 | 482 | 19.7 | ||
Lewy body dementia | 299 | 2.9 | 237 | 3.1 | 62 | 2.5 | ||
Other dementia | 691 | 6.8 | 529 | 6.9 | 162 | 6.6 | ||
Unspecified dementia | 1758 | 17.3 | 1302 | 16.9 | 456 | 18.7 | ||
Year of diagnosis | 2008 | 1215 | 1015 | 83.5 | 200 | 16.5 | χ2 = 371.8, p < 0.001 | |
2009 | 1177 | 970 | 82.4 | 207 | 17.6 | |||
2010 | 1346 | 1094 | 81.3 | 252 | 18.7 | |||
2011 | 1445 | 1162 | 80.4 | 283 | 19.6 | |||
2012 | 1476 | 1131 | 76.6 | 345 | 23.4 | |||
2013 | 1545 | 1153 | 74.6 | 392 | 25.4 | |||
2014 | 1515 | 944 | 62.3 | 571 | 37.7 | |||
2015 | 418 | 224 | 53.6 | 194 | 46.4 |
Cumulative incidence and admission rate of hospitalisation
Number of people ever admitted | 7693/10,137 |
---|---|
Cumulative incidence of any admission (%) (95% confidence interval) | 75.9 (75.0, 76.7) |
Person yearsa | 28,425.3 |
Total number of all admissions | 35,716 |
Admission rate (/PY) (95% confidence interval) | 1.26 (1.24,1.27) |
Number of emergencyb admissions | 25,634 |
Emergency admission rate (/PY) | 0.90 (0.89, 0.91) |
Number of electiveb admissions | 10,082 |
Elective admission rate (/PY) (95% confidence interval) | 0.35 (0.35, 0.36) |
Age-standardised admission ratio for dementia
Age-groups | People without dementia | People with dementia | Expected number of admissions | ||||||
---|---|---|---|---|---|---|---|---|---|
n | Number of admissions | Admission rate (/yr) | n | Number of admissions | Admission rate (/yr) | ||||
Emergency admissions | 65–69 | 32,441 | 5146 | 0.16 | 76 | 81 | 1.07 | 12.1 | Standardised emergency admission ratio (= observed/ expected × 100) |
70–74 | 27,148 | 5962 | 0.22 | 186 | 145 | 0.78 | 40.8 | ||
75–79 | 20,744 | 6199 | 0.30 | 300 | 254 | 0.85 | 89.7 | ||
80–84 | 14,178 | 6209 | 0.44 | 380 | 324 | 0.85 | 166.4 | ||
85–89 | 7591 | 4649 | 0.61 | 331 | 340 | 1.03 | 202.7 | ||
90 + | 3787 | 3068 | 0.81 | 172 | 199 | 1.16 | 139.3 | ||
Total | 105,889 | 31,233 | 1445 | 1343 | 651 | 2.06 (1.95, 2.18) | |||
Elective admissions | 65–69 | 32,441 | 16,938 | 0.52 | 76 | 41 | 0.54 | 39.7 | Standardised elective admission ratio (= observed/expected × 100) |
70–74 | 27,148 | 16,772 | 0.62 | 186 | 206 | 1.11 | 114.9 | ||
75–79 | 20,744 | 14,622 | 0.70 | 300 | 305 | 1.02 | 211.5 | ||
80–84 | 14,178 | 9931 | 0.70 | 380 | 189 | 0.50 | 266.2 | ||
85–89 | 7591 | 3668 | 0.48 | 331 | 62 | 0.19 | 159.9 | ||
90 + | 3787 | 865 | 0.23 | 172 | 25 | 0.15 | 39.3 | ||
Total | 105,889 | 62,796 | 1445 | 828 | 831 | 1.00 (0.93, 1.07) |
Association of sociodemographic and clinical factors with hospitalisation
Emergency hospitalisation
Characteristic | Emergency hospital admissions | Elective hospital admissions | |||
---|---|---|---|---|---|
IRR (95% CI) | p value | IRR (95% CI) | p value | ||
Age (per 1 year increment) |
1.03 (1.02, 1.03)
| < 0.001 |
0.96 (0.95, 0.98)
| < 0.001 | |
Sex | Female |
0.77 (0.71, 0.84)
| < 0.001 |
0.58 (0.49, 0.70)
| < 0.001 |
Ethnicity | White (Ref.) | 1 | 1 | ||
Asian |
0.79 (0.66, 0.96)
|
0.02
| 1.23 (0.85, 1.77) | 0.27 | |
African/Caribbean |
0.80 (0.72, 0.90)
| < 0.001 |
1.43 (1.13, 1.81)
|
0 003
| |
Other |
0.69 (0.55, 0.87)
|
0.001
| 1.24 (0.79, 1.94) | 0.35 | |
Marital status | Married (Ref.) | 1 | 1 | ||
Divorced | 1.13 (0.97, 1.30) | 0.11 | 1.33 (0.98, 1.82) | 0.07 | |
Widowed | 1.10 (1.00, 1.21) | 0.05 | 1.03 (0.84, 1.27) | 0.79 | |
Single | 1.10 (0.98, 1.23) | 0.11 | 0.95 (0.75, 1.21) | 0.68 | |
Deprivation score (per 10-unit increase in deprivation) |
1.05 (1.01, 1.09)
|
0.006
|
0.92 (0.86, 0.99)
|
0.04
| |
MMSE (per 1 unit decrease) | 1.01 (1.00, 1.01) | 0.05 |
0.95 (0.94, 0.97)
| < 0.001 | |
Problem with (from HoNOS subscale)a: | Agitated behaviour | 1.02 (0.92, 1.13) | 0.72 | 0.93 (0.74, 1.17) | 0.56 |
Self-injury | 1.24 (0.92, 1.68) | 0.16 | 0.64 (0.30, 1.36) | 0.24 | |
Problem-drink/drugs | 1.12 (0.91, 1.38) | 0.30 | 1.43 (0.92, 2.23) | 0.11 | |
Physical illness |
1.73 (1.59, 1.88)
| < 0.001 |
1.81 (1.51, 2.18)
| < 0.001 | |
Hallucinations | 1.03 (0.92, 1.15) | 0.56 | 0.84 (0.66, 1.06) | 0.14 | |
Depressed mood |
1.14 (1.02, 1.26)
|
0.02
|
0.67 (0.53, 0.85)
|
0.001
| |
Daily living |
1.18 (1.08, 1.28)
| < 0.001 |
1.33 (1.10, 1.62)
|
0.004
| |
Living conditions |
1.16 (1.04, 1.30)
|
0.008
| 0.82 (0.64, 1.05) | 0.11 | |
Last recorded dementia diagnosis | Alzheimer’s disease (Ref.) | 1 | 1 | ||
Vascular dementia |
1.41 (1.28, 1.55)
| < 0.001 |
2.18 (1.75, 2.72)
| < 0.001 | |
Lewy body dementia | 1.18 (0.95, 1.47) | 0.13 | 1.46 (0.93, 2.29) | 0.10 | |
Other dementia | 1.08 (0.93, 1.25) | 0.33 | 1.17 (0.84, 1.62) | 0.35 | |
Unspecified dementia |
1.55 (1.40, 1.73)
| < 0.001 |
1.43 (1.11, 1.83)
|
0.005
| |
Year of diagnosis (per 1 year later) | 2008 (Ref.) | 1 | 1 | ||
2009 |
1.18 (1.01, 1.38)
| 0.99 (0.71, 1.39) | |||
2010 |
1.26 (1.08, 1.47)
| 1.37 (0.99, 1.90) | |||
2011 |
1.21 (1.04, 1.41)
|
1.78 (1.30, 2.43)
| |||
2012 |
1.32 (1.14, 1.53)
|
1.54 (1.13, 2.11)
| |||
2013 |
1.28 (1.10, 1.48)
|
1.50 (1.09, 2.06)
| |||
2014 |
1.29 (1.11, 1.50)
| 1.34 (0.97, 1.84) | |||
2015 |
1.39 (1.12, 1.73)
| 0.91 (0.56, 1.47) | |||
Per one year later |
1.03 (1.01, 1.05)
|
0.001
| 1.04 (1.00, 1.08) | 0.07 |