In our population of elderly medical in-patients, we found low values for BMI, Na, eGFR and Hgb to be independent and statistically significant risk factors for one-year mortality.
In contrast to the commonly reported J or U shaped associations between BMI and survival with higher mortality at both extremes (16, 17), we found a close to linear relationship. The patients with the highest BMI had the best survival chance. One previous Norwegian cohort study reported the same pattern, with the highest mortality in patients with BMI < 20 kg/m2 (12). A meta-analysis of BMI and mortality in persons aged > 65 from 2017 demonstrated increased mortality in persons with a BMI < 22 kg/m2 and the lowest mortality risk in persons with BMI 28–29 kg/m2. On the other extreme, an increased mortality risk was first reached when BMI exceeded 33 kg/m2 (37). Among our patients, only 7 had a BMI of that magnitude, reducing our possibility to find an excess mortality risk associated with high BMI. In particular for multimorbid patients, our findings support that a high BMI seems to be beneficial. For treatment plans after discharge we suggest to emphasize information regarding weight and nutritional status.
Anaemia is frequent in individuals living in the community and the prevalence is increasing in elderly people (26). Anaemia in the elderly affects cognition, emotions and leads to impaired function (38). In our patient population, anaemia was significantly associated with one-year mortality. A German initiative has proposed to include anaemia as a geriatric syndrome (38). Our results supports this, and we recommend that assessment of anaemia becomes a natural part of the patient`s treatment plan after discharge.
Hyponatremia is the most common electrolyte abnormality observed in clinical practice (28). Hyponatremia is related to several chronic diseases whereof some have an increasing prevalence with increasing age, like stroke, heart disease, chronic kidney disease and cancer. Normal symptoms for patients with hyponatremia include dizziness, disturbed alertness and confusion, which increases the risk of falls (29). Patients with hyponatremia have longer stays, more readmissions and increased mortality (30–32, 39). One of the major causes of hyponatremia is diuretic therapy, often in combination with psychoactive drugs. Many elderly use at least one diuretic drug (40). Our suggestion is that patients with polypharmacy and hyponatremia should get a thorough medication review.
eGFR is one of the most used ways to measure kidney function, and has been shown to be related to mortality in different patient groups (13) and at different stages of disease (14, 15). In older patients, a low eGFR might be regarded as much as a marker for age-related loss of physiologic reserves than as a predictor of specific renal outcomes. It appears, however, also to exist a reciprocal relationship between aging and chronic kidney disease, as the presence of geriatric complications is also high in younger patients with end stage renal disease (41). For elderly multimorbid patients, it is important that eGFR is measured and the result is taken into account when deciding on treatment goals and drug therapy.
Most of our risk factors candidates are considered as frailty indicators (42). Frailty has been shown to be associated with higher mortality, longer in-hospital stay and more complications, also in individuals without multimorbidity (19, 21, 43). Moreover, previous studies have found multimorbidity (3), polypharmacy (5, 44), functional decline (7), low handgrip strength (20), sarcopenia (18, 45) and cognitive decline (8) to be associated with one-year mortality. None of these frailty indicators were associated with one-year mortality in our study population. In contrast to other studies that have included more unselected patients (45–47), our aim was to study mortality in selected patients that all suffered from mild to severe frailty. Our inclusion criteria (multimorbidity and dependence upon home nursing) were chosen accordingly. More than 40% scored underneath the threshold for being “weak” according to the European Working Group on Sarcopenia in Older People definition (48), and many were cognitively impaired as indicated by a median MMSE-NR score of 23. Cognitive impairment and multimorbidity interact negatively and have impact on older adults’ health status, quality of life and survival (49). Our findings should be interpreted bearing in mind that the studied cohort represents a selection of a mildly to more severely frail subsample of elderly hospitalised patients.
Our results support the consistent previous findings regarding an increased risk of mortality among individuals with low BMI, hyponatremia, impaired renal function and low Hgb. It is likely that these factors are indicators for disease or frailty that contribute to mortality. Hence, we suggest these four elements always to be assessed and considered as part of every treatment plan for frail elderly discharged from hospital, and for patients on polypharmacy these abnormalities should give extra attention during the medication review.
Strengths and limitations
This research project was a cooperation between six municipalities and the hospital. In order to be included, the patients had to receive home care services prior to the admission. These inclusion criteria might have increased the proportion of patients with a limited social network, a group that have a higher risk of complications and mortality. For ethical reasons, the patients had to be competent to give a valid, signed consent, obviously limiting the generalizability to patients with severe dementia and psychiatric disorders. Compared to previous studies, our population is older and has more pronounced multimorbidity and polypharmacy. We had a limited follow up, thus we were not able to register possible drug-related deaths or deaths related to acute illness during the year after inclusion. We also have no information on drug changes or visits to the primary health care physician.
Our population was old, with a mean age of 86 years, and thus representative for a geriatric patient group. The hospital is governmental financed, offering health services to all inhabitants regardless of economic or social status, thus giving a less selected sample than would else have been possible. The patients where frail and weak (48), representing a population that frequently is excluded from research. Compared to other studies, our study comprised patients with more severe comorbidity, lower muscle strength, a more pronounced polypharmacy and, accordingly, a high one year mortality. This weakens the generalizability of the results to all elderly, but it reinforces the validity for frail elderly patients.