The present invention relates to a method for transmission infrared spectroscopic analysis for determining the degree of global cognitive impairment associated with Alzheimers disease based on analyzing the 3100-1300 cm-1 infrared spectrum region of a previously obtained and fractionated sample of blood. Preferably, the fractionated sample of blood to be analyzed is a fraction of leukocytes.Likewise, another object of the present invention relates to the use of said method to obtain an indication of the status of the Alzheimers disease and/or an indication of the degree of cognitive impairment associated with said disease.
