Dementia is a disease that fulfils the parameters proposed by the CDC in order to assess the importance and need for an epidemiological surveillance system in terms of public health: frequency and severity, differences and dissimilarities amongst population groups, high cost, potential of primary and secondary prevention, and public interest.  The ReDeGi sets out from a conceptual model of registry, which fulfil the CDC guidelines for evaluating a surveillance system and is adapted to the particular needs of dementia.  Following a 2-year long test in which the operating structure of a registry system took the lead with satisfactory results , 2007 represented the start of activity of the ReDeGi in the entire RSG area which extends for 5,517 km2 and includes a population of 690,207 inhabitants. The results obtained are an innovation with regard to the existing dementia registries and can be evaluated from a point of view of methodology or from a practical utility perspective.
On the one hand, from a strictly methodology perspective, the ReDeGi has adopted a registry model different to those used by the South Carolina Alzheimer's Registry and by the New York State Dementias Registry. The first of these is based on the integration of computerised data originating from different sources of information. The information entered includes the diagnosis of dementia (ICD-9 criteria), other medical diagnoses and basic demographic data. The information that enables the elaboration of a registry is circumscribed to the stratification of dementia subtypes according to demographic and administrative characteristics such as gender, race or age, and to the origin of the particular case. Access to death certificates via a link also allows estimating the mortality rates of entered cases from a certain inclusion date in the registry onwards. [11, 12, 30] Even though the New York State Dementias Registry only admits cases of dementia (ICD-9 criteria) from discharge forms from all the hospitals in the state of New York, it does allow to carry out an estimate of the hospitalisations required by patients with dementia and their causes as well as the type of admission and destination at discharge. [9, 10] Unlike the previously mentioned registries, which are based on information from electronic databases, the ReDeGi is characterised by the compilation of data straight from the patient's medical chart by a ReDeGi technician. This method allows the standardised registration of clinical information available in the patient's medical history. Moreover, it is a procedure that permits the maintenance of a dementia subtypes registry in accordance with DSM-IV criteria and other diagnostic criteria specific to the subtypes of dementia that ICD-9 and administrative databases are unable to register. For example, in table 1 cases with the diagnostic category "Dementia caused by non-specified diseases" include a subcategory named "Lewy's bodies" that correspond to those cases that accomplished the diagnostic criteria for dementia with Lewy bodies, and the 23 cases under "dementia caused by Pick's disease" diagnostic category correspond to 18 cases that accomplished the diagnostic criteria for frontotemporal dementia and 5 cases the diagnostic criteria for primary progressive aphasia. In this sense, the data collection procedure implemented at the ReDeGI ensures greater validity of the information recorded in the registry related to the diagnosis.
On the other hand, from a strictly pragmatic point of view, the data obtained from the ReDeGi provide relevant information about the healthcare pressure brought about emerging dementia cases in a certain territory over a defined period of time. The ReDeGi provides evidence on the distribution of the dementia subtypes and the clinical and demographic characteristics of patients who contact specialist healthcare devices.
The analysis of the data shows that AD accounted for 60.1% of the entered cases, mixed dementia (AD + vascular component) for 10.7% and vascular dementia (VaD) for 4.6%. These percentages are similar to those from the South Carolina Alzheimer's Disease Registry, in which the AD cases entered in the period 1988–2003 accounted for 64% of the total and VaD cases accounted for the remaining 14%. In relation to the place of residence of the patients, the differences between the South Carolina Alzheimer's Disease Registry and the ReDeGi can reflect two distinct sociocultural and healthcare models. In the former model, 57% of the cases live in the community and 38% in assisted centres, whereas in the latter 83.1% live in the community (their own home or the home of a family member) and 6.6% live in long-term care centres. Data on the mean time between the onset of symptoms and clinical diagnosis indicate that for most dementias the mean time from onset to diagnosis is approximately 2 years. In this sense, it is hard to establish a precise date of dementia onset, although the estimate based on the data collected by the informant carer has proven to be a reliable source of information. 
The diagnostic coverage of the registry has been estimated to be 61.3% of the total expected cases in the territory, with differences being observed amongst the different healthcare sectors. However, there are certain limitations that should be taken into account when estimating the diagnostic coverage on the basis of expected number of dementia cases per year in the catchment area. Formally, in an epidemiological study, the incidence rate would be calculated dividing the number of cases detected in specified period by the free-of-disease inhabitants by time unit. However, the cases entered in the registry correspond to patients who were referred to a specialised diagnostic unit, some of whom presented moderate to severe severity and a mean time of 2 years from onset of symptoms to time of diagnosis. These are new cases of dementia for healthcare devices and consequently the results of the estimated diagnostic coverage are not representative of the real incidence in the general population. These results can however be reliably used to ascertain the incidence of new cases that contact specialised health services. A possible explanation for the number of cases not registered (38.7%) could be hypothetized that they correspond to mild or advanced cases of dementia. It may be that the first group did not attend specialised consultations due to the low impact of the symptoms of dementia in the early stages and the second group did not attend consultations because the benefit of a diagnostic could be more limited. It is interesting to note that we have observed a great variation in the diagnostic coverage across hospitals. These differences might due to different variables and may help to identify factors related to the referral and diagnosis in clinical practice. For example, these differences may be due to differences between types of specialist physicians (neurology or geriatrics) or due to the existence of specific devices for dementia diagnostic. However, it is important to emphasise that, for the ReDeGi, more than achieve a full diagnostic coverage, it is more important to register all cases that have been diagnosed in the 7 RSG hospitals. Thus, the ReDeGi will become a powerful information device in few years when it provides cumulative information about the pressure of dementia cases and its evolutionary course.