Background
Methods
Identification of the dataset (documents) under study
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Documents indexed in the MEDLINE database. The indicators obtained from this dataset enabled a general vision of the scientific output and subject areas in the biomedical literature with regard to this age group.
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Next, we generated a new dataset, excluding the retrieved documents that had also been assigned to other age groups (aged; middle aged; young adult; child; child, preschool; infant; infant, newborn) in order to specifically analyze the literature focusing exclusively on very old people, as a high number of publications jointly consider very old populations along with people from other age groups. Thus, epidemiological studies, basic research and other documents in which advanced age was not an exclusive key variable were excluded. To calculate the indicators, we opted to include only the documents in the Web of Science-Core Collection (WoS-CC). Although this database does not encompass all of the documents indexed in MEDLINE, it does offer some additional functionalities that are relevant to the study aims. For example, it classifies documents into areas of knowledge or disciplines, based on the subject area focus of the journals in which they were published. The WoS-CC also records all authors’ institutional affiliations and their corresponding countries, along with the number of citations that the documents receive. Figure 1 shows a flow chart for the selection of the study dataset.
Analysis and treatment of bibliographic data
Indicators and analysis
Bibliometric analysis of scientific output
Characterization of subject areas: research clusters
Ethics
Results
Scientific output
Geographic area | 2000–2004 | 2005–2009 | 2010–2014 | 2015–2019 | TOTAL | |||||
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N | % | N | % | N | % | N | % | N | % | |
North America | 7 | 46.7 | 1772 | 35.5 | 2484 | 30 | 2423 | 28.3 | 6686 | 30.5 |
Europe | 4 | 26.7 | 2157 | 43.2 | 3805 | 46 | 3599 | 42.1 | 9565 | 43.7 |
Asia | 4 | 26.7 | 1060 | 21.2 | 1947 | 23.5 | 2688 | 31.4 | 5699 | 26 |
Oceania | 1 | 6.7 | 206 | 4.1 | 361 | 4.4 | 403 | 4.7 | 971 | 4.4 |
Africa | 0 | 0 | 15 | 0.3 | 38 | 0.5 | 50 | 0.6 | 103 | 0.5 |
L. America & Caribbean | 1 | 6.7 | 73 | 1.7 | 197 | 2. | 236 | 2.8 | 507 | 2.3 |
TOTAL | 15 | 0.1 | 4995 | 22.9 | 8268 | 37.9 | 8555 | 39.2 | 21,833 | 100 |
Country | 2000–2004 | 2005–2009 | 2010–2014 | 2015–2019 | TOTAL | ||||||
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N | % | N | % | N | % | N | % | N | % | N publications per million inhabitants | |
USA | 6 | 40 | 1627 | 32. | 2233 | 27 | 2177 | 25.4 | 6043 | 27.7 | 18.4 |
Japan | 2 | 13.3 | 594 | 11.9 | 1011 | 12.2 | 1471 | 17.2 | 3078 | 14.1 | 24.4 |
UK | 2 | 13.3 | 526 | 10.5 | 647 | 7.8 | 558 | 6.5 | 1733 | 7.9 | 25.9 |
Italy | – | – | 361 | 7.2 | 605 | 7.3 | 630 | 7.4 | 1596 | 7.3 | 26.5 |
Germany | – | – | 239 | 4.8 | 524 | 6.3 | 563 | 6.6 | 1326 | 6.1 | 15.9 |
France | – | – | 225 | 4.5 | 555 | 6.7 | 527 | 6.2 | 1307 | 6 | 19.5 |
Spain | 1 | 6.7 | 193 | 3.9 | 508 | 6.1 | 587 | 6.9 | 1289 | 5.9 | 27.4 |
Australia | 1 | 6.7 | 185 | 3.7 | 314 | 3.8 | 360 | 4.2 | 860 | 3.9 | 33.9 |
Canada | 1 | 6.7 | 175 | 3.5 | 303 | 3.7 | 328 | 3.8 | 807 | 3.7 | 21.5 |
China | – | – | 82 | 1.6 | 247 | 3 | 453 | 5.3 | 782 | 3.6 | 0.6 |
Netherlands | – | – | 145 | 2.9 | 243 | 2.9 | 216 | 2.5 | 604 | 2.8 | 34.8 |
Switzerland | – | – | 93 | 1.9 | 170 | 2.1 | 180 | 2.1 | 443 | 2 | 79.5 |
Sweden | – | – | 97 | 1.9 | 160 | 1.9 | 184 | 2.1 | 441 | 2 | 42.9 |
Taiwan | 1 | 6.7 | 115 | 2.3 | 164 | 2 | 161 | 1.9 | 441 | 2 | 19.1 |
Belgium | – | – | 75 | 1.5 | 163 | 2 | 127 | 1.5 | 365 | 1.7 | 31.8 |
Turkey | 1 | 6.7 | 78 | 1.6 | 154 | 1.9 | 131 | 1.5 | 364 | 1.7 | 4.4 |
South Korea | – | – | 47 | 0.9 | 127 | 1.5 | 174 | 2 | 348 | 1.6 | 6.7 |
Greece | – | – | 109 | 2.2 | 119 | 1.4 | 92 | 1.9 | 320 | 1.5 | 29.9 |
Israel | – | – | 69 | 1.4 | 98 | 1.2 | 125 | 1.5 | 292 | 1.3 | 32.2 |
Brazil | – | – | 37 | 0.7 | 125 | 1.5 | 130 | 1.5 | 292 | 1.3 | 1.4 |
Austria | – | – | 51 | 1 | 79 | 1 | 92 | 1.1 | 222 | 1 | 25.0 |
Finland | – | – | 36 | 0.7 | 83 | 1 | 88 | 1. | 207 | 0.9 | 37.5 |
Portugal | – | – | 17 | 0.3 | 59 | 0.7 | 110 | 1.3 | 186 | 0.8 | 18.11 |
Denmark | – | – | 44 | 0.9 | 59 | 0.7 | 76 | 0.9 | 179 | 0.8 | 30.8 |
Singapore | – | – | 26 | 0.5 | 53 | 0.6 | 83 | 1 | 162 | 0.7 | 28.4 |
Poland | – | – | 15 | 0.3 | 60 | 0.7 | 65 | 0.8 | 140 | 0.6 | 3.7 |
Norway | – | – | 25 | 0.5 | 52 | 0.6 | 62 | 0.7 | 139 | 0.6 | 26.0 |
New Zealand | – | – | 21 | 0.4 | 60 | 0.7 | 57 | 0.7 | 138 | 0.6 | 28.1 |
Ireland | 1 | 6.7 | 32 | 0.6 | 44 | 0.5 | 45 | 0.5 | 122 | 0.6 | 24.7 |
India | – | – | 27 | 0.5 | 46 | 0.6 | 45 | 0.5 | 118 | 0.5 | 0.1 |
Disciplines and topic areas
Web of Science Category | N docs * | % | N Journals | Docs/Journal |
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Cardiac & Cardiovascular Systems | 2395.7 | 10.9 | 138 | 17.4 |
Medicine, General & Internal | 1924.1 | 8.7 | 165 | 11.7 |
Surgery | 1824.4 | 8.3 | 210 | 8.7 |
Geriatrics & Gerontology † | 1664.5 | 7.5 | 51 | 32.6 |
Dermatology | 1410.8 | 6.4 | 68 | 20.7 |
Clinical Neurology | 861 | 3.9 | 204 | 4.2 |
Gerontology † | 812.8 | 3.7 | 36 | 22.6 |
Ophthalmology | 742.8 | 3.4 | 60 | 12.4 |
Gastroenterology & Hepatology | 641.7 | 2.9 | 88 | 7.3 |
Pathology | 549.6 | 2.5 | 78 | 7 |
Oncology | 505.4 | 2.3 | 244 | 2.1 |
Peripheral Vascular Disease | 500.6 | 2.3 | 65 | 7.7 |
Radiology, Nuclear Medicine & Medical Imaging | 498.9 | 2.3 | 133 | 3.7 |
Neurosciences | 484 | 2.2 | 271 | 1.8 |
Orthopedics | 450.6 | 2 | 82 | 5.5 |
Pharmacology & Pharmacy | 410 | 1.9 | 270 | 1.5 |
Urology & Nephrology | 409.3 | 1.9 | 85 | 4.8 |
Anesthesiology | 355.9 | 1.6 | 32 | 11.1 |
Emergency Medicine | 330.7 | 1.5 | 31 | 10.7 |
Hematology | 327 | 1.5 | 76 | 4.3 |
Respiratory System | 293.7 | 1.3 | 64 | 4.6 |
Infectious Diseases | 259 | 1.2 | 93 | 2.8 |
Dentistry, Oral Surgery & Medicine | 252.5 | 1.1 | 91 | 2.8 |
Nursing | 250.1 | 1.1 | 123 | 2 |
Psychiatry | 227.5 | 1 | 155 | 1.5 |
Geriatric diseases, health services for the aged and social and psychological issues of aging
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Neurocognitive disorders (including dementias and especially Alzheimer’s disease), cognitive dysfunction, and depression all have a prominent presence in this cluster, as do descriptors referring to different tools for diagnosing dysfunctions, brain damage, and central nervous system disorders, and for assessing the severity of mental illnesses and measuring pain.
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Another area of research interest is fractures (particularly femoral fractures) caused by accidental falls. Papers focus on the procedures for their treatment, including orthopedic surgery using bone fixation devices to maintain proper fracture alignment.
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Numerous descriptors refer to the study of nutritional physiological phenomena associated with nutrient absorption and the assessment of nutritional status.
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The loss of skeletal muscle mass, especially in relation to sarcopenia, represents another specific area of research identified.
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Other descriptors have to do with the study of genetic factors associated with longevity, genetic predisposition, and conditions that can trigger the activation of disease.
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Finally, another thematic area concerns health services for the aged in the hospital setting as well as in institutional care and home care and social and psychological issues of aging.
Cardiovascular diseases
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Heart diseases. Different diseases and pathologies associated with heart valves and conditions linked to “myocardial ischemia” stand out among this cluster.
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Vascular diseases. This cluster also features different vascular diseases, like “aortic aneurysm,” both abdominal and thoracic; “iliac aneurysm”; and “carotid stenosis.”
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Cerebrovascular disorders. Finally, cerebrovascular disorders, especially “stroke” and “brain ischemia,” comprise a prominent area of study with its own specific lines of research.
Neoplasms
Bacterial infections & anti-bacterial agents
Research clusters and sub-topics | N docs | % | N Citations | Citations per doc |
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A) Geriatric diseases, health services for the aged and social and psychological issues of aging | 8381 | 38 | 143,734 | 17.1 |
- Health services for the aged & social and psychological issues of aging | 5414 | 24.6 | 95,003 | 17.5 |
- Neurocognitive & depressive disorders | 3094 | 14 | 62,695 | 20.3 |
- Muscle atrophy problems | 874 | 4 | 16,071 | 18.4 |
- Falls & fractures | 841 | 3.8 | 12,615 | 15 |
- Genetic factors | 555 | 2.5 | 13,806 | 24.9 |
- Nutrition | 349 | 1.6 | 5829 | 16.6 |
B) Cardiovascular diseases | 6963 | 31.6 | 69,513 | 10 |
- Vascular diseases | 5681 | 25.8 | 55,022 | 9.7 |
- Heart diseases | 5380 | 24.4 | 56,313 | 10.5 |
C) Neoplasms | 5205 | 23.6 | 34,882 | 6.7 |
D) Bacterial Infections & Anti-Bacterial Agents | 1216 | 5.5 | 11,220 | 9.2 |
Diseases with greater incidence in people under 80 years of age and with sex-related differences
MeSH descriptor | N docs total | N docs only female | N docs only male | % only female* | % only male* | Dif % female – male† | P value |
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Aortic Valve Stenosis | 1134 | 260 | 191 | 22.9 | 16.8 | 6.1 | < 0.001‡ |
Skin Neoplasms | 951 | 396 | 499 | 41.6 | 52.5 | −10.8 | < 0.001‡ |
Dementia | 697 | 91 | 48 | 13.1 | 6.9 | 6.2 | < 0.001‡ |
Alzheimer Disease | 575 | 103 | 65 | 17.9 | 11.3 | 6.6 | 0.001‡ |
Stroke | 500 | 121 | 99 | 24.2 | 19.8 | 4.4 | 0.093 |
Carcinoma, Squamous Cell | 435 | 196 | 189 | 45.1 | 43.4 | 1.6 | 0.63 |
Adenocarcinoma | 417 | 165 | 214 | 39.6 | 51.3 | −11.7 | < 0.001‡ |
Accidental Falls | 376 | 116 | 45 | 30.8 | 12 | 18.9 | < 0.001‡ |
Cognition Disorders | 365 | 35 | 35 | 9.6 | 9.6 | 0 | 1 |
Lung Neoplasms | 365 | 117 | 171 | 32 | 46.8 | −14.8 | < 0.001‡ |
Heart Failure | 352 | 89 | 89 | 25.3 | 25.3 | 0 | 1 |
Hypertension | 325 | 85 | 60 | 26.1 | 18.5 | 7.7 | 0.018‡ |
Hip Fractures | 323 | 63 | 17 | 19.5 | 5.3 | 14.2 | < 0.001‡ |
Myocardial Infarction | 295 | 80 | 78 | 27.1 | 26.4 | 0.7 | 0.86 |
Aortic Aneurysm, Abdominal | 270 | 37 | 178 | 13.7 | 65.9 | −52.2 | < 0.001‡ |
Prosthesis Failure | 264 | 114 | 103 | 43.2 | 39 | 4.2 | 0.33 |
Melanoma | 253 | 100 | 134 | 39.5 | 53 | −13.4 | 0.003‡ |
Hemorrhage | 221 | 81 | 70 | 36.6 | 31.7 | 4.9 | 0.27 |
Depression | 218 | 28 | 16 | 12.8 | 7.3 | 5.5 | 0.056 |
Coronary Artery Disease | 215 | 35 | 58 | 16.3 | 27 | −10.7 | 0.007‡ |
Cardiovascular Diseases | 199 | 17 | 9 | 8.5 | 4.5 | 4 | 0.11 |
Breast Neoplasms | 198 | 192 | 2 | 97 | 1 | 96 | < 0.001‡ |
Carcinoma. Basal Cell | 197 | 80 | 99 | 40.6 | 50.2 | −9.6 | 0.054 |
Stomach Neoplasms | 195 | 69 | 82 | 35.4 | 42 | −6. | 0.18 |
Neoplasm Recurrence, Local | 192 | 96 | 80 | 50 | 41.7 | 8.3 | 0.10 |
Prostatic Neoplasms | 168 | – | 164 | 0 | 97.6 | −97.6 | < 0.001‡ |
Liver Neoplasms | 167 | 65 | 92 | 38.9 | 55.1 | −16.8 | 0.003‡ |
Calcinosis | 163 | 78 | 49 | 47.8 | 30.1 | 17.7 | 0.001‡ |
Cognitive Dysfunction | 163 | 12 | 6 | 7.4 | 3.7 | 3.7 | 0.14 |
Neoplasm Invasiveness | 162 | 72 | 68 | 44.4 | 42 | 2.5 | 0.65 |