Introduction:
We aimed to analyze the prevalence of unexplained anemia (UA) and assess its characteristics, potential causes and impact on survival in an elderly population.

Material and methods:
Medical files of 981 patients aged ≥ 60 years consulted in one primary medical clinic in Poland in 2013–2014 were retrospectively analyzed. Anemia, defined according to WHO criteria, diagnosed during either hospitalization or outpatient treatment, from the age of 60, was included. Unexplained anemia was diagnosed if, based on available clinical data and laboratory tests and other assessments in medical records, none of the well-known types of anemia were identified.

Results:
Of 981 patients with anemia, UA was found in 48 (28.4%) patients (4.9% of those studied) and incidence increased with age (≥ 80 years, 12.3%). In 81.3% no full hematological diagnostics were performed. Patients with UA, as with those with defined anemia, when compared to the group without anemia were older, had more co-morbidities, were more frequently hospitalized, more frequently had dementia syndrome and obtained lower Barthel scores (p < 0.0001). In the groups of patients with UA and defined anemia, there were more deaths than in those without anemia (10% vs. 13% vs. 2%, p < 0.0001) with significant differences in survival rates observed during 3-year follow-up.

Conclusions:
The increasing incidence with age of UA in the elderly population, insufficient diagnosis and the higher mortality of patients with UA in comparison to the group without anemia indicate the need to develop recommendations for its management by primary care physicians.