In the past decades hospital malnutrition has become a subject of numerous epidemiological and clinical studies. This is due to the fact that a considerable part of patients admitted to hospitals manifest clinical or biochemical symptoms of malnutrition (1, 2). In many patients the symptoms of malnutrition, ascertained while being admitted to hospital, become intensified in the hospitalisation period. Besides as the stay in hospital increases, the occurrence frequency of malnutrition tends to grow as well (3, 4). It was found that malnutrition in patients tends to increase the morbidity, prolongs the required stay in hospital, and also increases treatment costs (5, 6).

In Poland tests of the nutritional status of the patients staying in hospitals were undertaken under a Commissioned Research Project Development of the scientific basis for nutrition in hospitals, which was oriented at evaluating the hospitalisation influence on the nutritional status (2, 7). The research was of a multi-centred, prospective and randomised nature. It was performed in 16 Polish hospitals, in clinics or internal medicine, general surgery, otolaryngological, gynaecology, ophthalmology and neurology wards.

The tests were performed on each tenth patient admitted to particular clinics or wards in the period from 01.01.1999 to 31.12.2000 (2, 7). The tests comprised 3256 patients aged 16 to 100, including 1368 males (average age: 54 years) and 1888 females (average age: 53 years). For each patient qualified for testing, in the first 24 hours after admission an assessment was carried out of the nutritional status, and with regard to persons after surgery – also on the date of discharge from the hospital. On the other hand, as regards persons who did not undergo surgery the nutritional status testing was carried out during discharge only if they stayed in the hospital longer than 10 days. The evaluation of the nutritional status at discharge from hospital was carried out on 2673 patients. The nutritional status was evaluated with the use of anthropometric methods (Body Mass Index – BMI (kg/m²); arm circumference (cm)) and biochemical methods (red cells count (million/mm³), haemoglobin concentration (g/dl), white cells count (x10³/mm³), lymphocyte count in peripheral blood (x10³/mm³), and albumin concentration in blood serum (g/dl)). In in-depth tests on the nutritional status several biochemical tests were carried out, which comprised the determination of levels of antioxidant vitamins (A, E, C), B₁₂ vitamin and folic acid in blood serum.

In patients for which the tests were carried out twice, it was found that during the stay in hospital a weight loss took place and consequently also the reduction of BMI, and arm circumference was reduced (2). In the tested blood the concentration of haemoglobin and albumins was reduced, and also the red cells count. Changes in the average lymphocyte count were not significant statistically.

The existence of a correlation was proven between the lengh of hospital stay and a change of certain nutritional indices (2, 7). As the number of days spent in hospital increased, a reduction of weight, BMI and arm circumference was noted (p < 0.05).

In a part of the patients the malnutrition risk was ascertained already during admittance to the hospital (tab. 1) (2). The value of BMI suggesting the possibility of protein-energy malnutrition was recorded in 4.2% of males and 4.4% of females. A decrease of lymphocytes count was recorded in the blood of 20% of males and 21.7% of females, and a deficient albumin concentration in the blood serum was noted in 23.1% of males and 18.6% of females. At discharge the percentage of persons with underweight was slightly higher, especially among males, nevertheless the differences were not of statistical significance. On the other hand, the percentage of patients, in which deficient albumin concentration was recorded, was significantly higher.

The percentage of persons, in which at least one of the above parameters pointed to the risk of malnutrition, amounted to 39.5% among males and 37.9% among females at admittance to hospital and to 43.9% and 44.1% respectively at discharge (2).

Weight loss during hospital stay was recorded in 60.9% of patients (2). On average it equalled to 2.1% of weight measured at the time of admittance. This reduction also concerned other persons characterised by underweight, and tended to intensify during hospitalisation. This concerned 42.6% of patients from this subgroup, and their weight decreased on average by 2.6%.

In the majority of cases the risk of vitamin malnutrition concerned vitamin C and folic acid (2). At admittance to hospital the deficit concentrations of those vitamins were recorded in 51.8% and 32% respectively of patients qualified for in-depth study. At discharge from hospital those percentages grew insignificantly (lack of statistical significance): for vitamin C to 67.7% and for folic acid to 40%.

The BMI correlates relatively well with other health state indices. In the analysed tests the interpretation proposed by WHO was adopted, according to which values of BMI < 18.5 kg/m² point to the risk of malnutrition (8). In the tested patient group BMI was clearly lower at discharge from hospital (2). Moreover, a strong interdependency was found to exist between the lengh of hospital stay and BMI reduction. The percentage of underweight persons already during admittance to hospital was higher in the general population, especially in older age groups (2, 9). During hospitalisation it even increased slightly (2).

During hospital stay arm circumference, another indicator of the protein-energy nutritional status decreased (2). The longer was the hospitalisation, the greater was the decrease in arm circumference.

The haemoglobin concentration is considered to be the most useful indicator in screening used to allow an evaluation of iron deficiency anaemia and an assessment of the nutritional status (7, 8). However, its values depend on the age of the tested persons, their gender and race and tend to change clearly during pregnancy. The haemoglobin concentration among tested patients during their stay in hospital clearly decreased (2).

In malnutrition the lymphocyte count in peripheral blood decreases (7, 8). The total lymphocyte count equalling to 1.5 x 10³/mm³ is considered to be correct. Values ranging between 0.9-1.5 x 10³/mm³ may indicate moderate nutritional disorders, while values below 0.9 x 10³/mm³ – severe malnutrition. However, the number of lymphocytes depends on numerous factors, such as septic states, stress, the administration of adrenal steroids, as well as coexistent infections. The evaluation of the total count of lymphocytes is a good measure of the immunity of the body and may only be used as an indirect measure of the nutrition status. A considerable part (ca. 20%) of tested patients was characterised by an insufficient lymphocyte count (2). Neither the average number of lymphocytes nor the percentage of patients in which it remained below the recommended values underwent substantial changes during the stay in hospital.

A frequently used index of the protein nutritional status are blood albumins (7, 8). There are many factors that affect the concentration of albumins in the blood serum, such as hepatic diseases, hypothyroidism (impaired production), diseases of the gastrointestinal tract and the kidneys (intensified albumins loss), injuries, stress, infections (change in the distribution of white cells in particular sections of the body), pregnancy (by dilution), in dehydration states (haemoconcentration). The albumin concentration of 3.5 g/dl was found to be the lowest admissible one, which can be accepted as being correct, while values ranging between 2.8-3.5 g/dl indicate to the possibility of protein malnutrition, and below 2.8 g/dl point to severe protein malnutrition. During hospitalisation the average concentration of albumins in the blood serum of the patients decreased considerably, and simultaneously quite a clear increase was recorded (by ca. 8 percentage points) of the percentage of patients, in whom this concentration was deficit (2).

Similar observations concerning the anthropometric indices of the nutritional status were made in patients admitted to one of the university hospitals in Scotland at the beginning of the nineties (3). The studied persons were characterised by an inferior nutritional status already at their admittance to the hospital as compared to the general population. Moreover, at the time of admission 39% of the group of patients with a correct weight had a lower weight during discharge, while in the group of underweight patients it became reduced in as much as 75%.