Senile frailty is a special state of decrepitude of the body caused by aging, which is usually associated with the loss of the body's physiological reserve and a lower tolerance for stressful events. The most common definition requires the presence of 3 or more of the 5 indicators - weight loss, emaciation, weakness, sluggishness, and physical inactivity. Frailty is a risk factor for many health outcomes, including falls, disability, long-term care needs, and death. 
Frailty increases dramatically with age, with a prevalence of 5.2% in men and 9.6% in women over the age of 65.. These rates rise to 40% in adults aged 80 and over. Frailty increases the risk of falls, delirium, disability, and other geriatric syndromes. It also increases vulnerability of age-related diseases such as neurodegeneration, myocardial infarction, stroke, type-2 diabetes, hypertension and susceptibility to viral or bacterial disease due to immune system decline. However, some very old people (> 90 years) do not have comorbidities, which probably explains why they live longer than average. However, at some point, they "suddenly" become "brittle", and it is not yet clear why. It is interesting to note that the offspring of centenarians seem to inherit the ability to resist senile infirmity - they are less prone to decrepitude than the offspring of non-centenarians. Obviously, centenarians, due to the inherited genome, are better able to cope with the increasing energy costs with aging to maintain health. So, for example, many centenarians are carriers of the longevity-associated variant of the BPIFB4 gene, as a result of which they have a reduced number of immune cells with CD38 destroying NAD+ protein on the outer membrane and, as a result, have a significantly higher level of NAD+ circulating in the blood, which contributes to longevity.
Criteria of frailty
The most commonly used criteria
1. Weakness: a.) Patient reports "some difficulty", "major difficulty" or "unable to do" when asked about difficulty lifting or carrying anything up to 5 kg; b.) grip strength assessed in the dominant hand using dynamometer, where "weak" is defined as the lowest 20% of the original population adjusted for body mass index. Usually the norm is 34 ± 5 kg for men and 22 ± 5 kg for women.
2. Poor stamina: a.) The patient reports "some difficulty" or "major difficulty" when asked about difficulty moving from one room to another. b.) The patient reports any of the following in the last month: low energy, unusual tiredness, or unusual weakness.
3. Slowness: a.) slowest 20% based on the time needed to complete a 4-6 meter walk, adjusted for floor and standing height. b.) on the "up-and-go" test (get up and go) if it exceeds 12 seconds.
4. Low physical activity: 'less active' response to the question 'compared to most men or women your age, would you say you are more active, less active, or about the same'.
5. Weight loss: unintentional weight loss of at least 10% after age 60 or BMI less than 18.5 kg/m2.
6. Static balance test. The ability to maintain balance affects the risk of falls and other adverse health effects. The inability to stand unsupported on one leg for 10 seconds was associated with an 84% increased risk of death from any cause over the next decade. According to the authors of the test, the proportion of those who cannot stand on one leg for 10 seconds was: about:
- 5% among 51-55 year olds;
- 8% among 56-60 year olds;
- 17% among 61-65 year olds; and
- 36% among 66-70 year olds;
- 53% of people aged 71-75.
Another criterion used is the presence of the smurf phenotype (smurfness) - the pre-death period of life, when the intestinal mucosa ceases to function properly and as a result of a sharp increase in intestinal permeability ("leaky gut syndrome"), there is an increase in the translocation of microbial products such as lipopolysaccharides from the gut into the bloodstream, which subsequently causes chronic, subacute systemic inflammation not associated with infection, called inflammaging. This criterion is more commonly used to detect frailty in small creatures such as flies. The smurf phenotype in flies is identified by blue coloring of the body after being fed a non-toxic blue food coloring, which in young flies does not normally enter the bloodstream from the gastrointestinal tract. Thus, frailty is a system-level measure that can also be applied to animals.
Comprehensive Geriatric Assessment (CGA)
Frailty in elderly individuals is generally identified using comprehensive geriatric assessments (CGA), which is a multidisciplinary diagnostic process to evaluate medical, functional, psychological and social capabilities. The CGA is based on evaluation of the health of older adults, exploring on 10 indicators (number of comorbidities, disability, mobility, balance, bowel/bladder function, nutrition, cognition, motivation, communication and social ability).
The Frailty Index based on a Comprehensive Geriatric Assessment (FI-CGA) is based on the CGA, evaluates the 10 dimensions and classifies patients into three classes of frailty: mild (0–7), moderate (7–13) and severe (>13)
It is interesting to note that centenarians, as persons with an extraordinary adaptive capacity, benefit from exceptional biological reserves that might be underestimated by clinical appearances and may live with debilitating disease, but still present an advantage in terms of incident disability and death. Apparently, this is why their biological FI is significantly lower than the clinical FI
Transitions in frailty phenotype states
Among the factors associated with frailty of old adults, younger age, never smoking, no history of diabetes, stroke, and COPD, respectively, predicted significantly higher chances of improving frailty status. Such findings are expected, since the cause-and-effect relationships of aging mechanisms have not yet been finally determined.
Prevention and treatment of frailty
The best means of preventing senile infirmity is moderate physical activity and a healthy diet, as well as training memory and the ability for cognition and learning.
Since an increased risk of fractures and falls leading to loss of mobility and increased hospitalizations is associated with a weakening of skeletal muscle and a decrease in their mass, the dietary supplement beta-hydroxy-beta-methylbutyrate (HMB) with anabolic and anti-catabolic properties has been proposed for long-term use, as one of the means of preventing senile frailty in people over 65 years, particularly in bedridden or sedentary. Daily intake of 2-3 grams of this drug improves muscle quality and does not have pronounced side effects. Since calcium β-hydroxy-β-methylbutyrate is less well absorbed by the body, it is advisable to use dietary supplements or high-protein foods to which β-hydroxy-β-methylbutyrate has been added, while calcium supplements to be given separately.
Cholecalciferol (vitamin D3) deficiency has been identified as a risk factor for accelerated muscle loss, poor physical performance and falls. Therefore, it is recommended that those patients with vitamin D3 levels below 30 ng/ml also take for three months vitamin D3 capsules (1000-2000 IU/day divided into two doses) or until its serum level reaches a sufficient range (30-60 ng/ml).
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