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This risk factor is associated with greater severity. However, according to different studies, its influence does not seem to be as clear as that of COPD, cardiovascular diseases or diabetes.

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OBESITY

Obesity is considered the epidemic of the 21st century, as its numbers are increasing in the adult population and, what is more worrying, in children. Being overweight/obese has been identified in numerous studies as a predictor of hospital admission and admission to the ICU, especially in patients under 65 years of age. The SEMI-COVID-19 registry shows its presence in 21% of patients.

The increased risk in these patients has been attributed to a higher level of

There is considerable variability in the prevalence of obesity, with some regions close to 20% and others to 15%. Even more important is the difference between sexes, both between regions and within the same region. It is important to note that there may be a certain geographical pattern according to the wealth of the territory: regions with lower obesity prevalence rates are those with higher Gross Domestic Product. There is a reason for this, as obesity is clearly linked to socio-economic variables.

In this case, the reporting bias is reduced –not fully eliminated– as the survey methodology specifies a limit for considering obesity or not. However, it is impossible to determine geographical patterns that imply statistically significant differences if no adjustment for age and sex is carried out.

DIABETES

This risk factor has been identified in 17% of the cases reported (8.9% of hospital admissions in Spain). It is clearly a higher risk factor for hospital admission, admission to the ICU and death. The biological mechanism on which this risk factor is based is that described for hypertension.

The prevalence of reported diabetes also shows important geographical differences, with regions registering a prevalence of around 5%, such as the Balearic Islands (Illes Balears), La Rioja and Cantabria, and others around 10%, such as Galicia and Extremadura. The difference between men and women may also be significant (see the Basque Country [Euskadi/País Vasco]).

Type II diabetes is basically a chronic age-associated pathology that could lie behind differences in mortality or lethality from COVID-19 between regions. However, as already mentioned in the comment on other variables, nothing can be inferred from the unadjusted data, which are subject to possible reporting biases.

HEART FAILURE

Heart failure has been described, either under this term or as a cardiovascular disease, as the most prevalent risk factor in the population diagnosed with COVID-19 (up to 30%) and is present in more than 50% of COVID-19 patients admitted to the ICU in Spain, according to several studies. Its mechanism of action is the same as for diabetes and hypertension.

Heart failure is more prevalent in women. However, as this figure is not adjusted by sex, it may be influenced by the higher life expectancy of women, since heart failure is more prevalent with age.

The primary healthcare model in Spain, based on the primary care team that covers the care of the population in a healthcare area, is the same in all regions and its information system has been consolidated for years. Significant geographical differences in prevalence may certainly be explained in part by differences in population structure; but it is very likely that there are other additional factors, e.g. lifestyle and those linked to the follow-up care of the population.

CHRONIC KIDNEY DISEASE

Chronic Kidney Disease (CKD) is included in the range of comorbidities that are associated with worse COVID-19 outcomes. Kidneys have ACE-2 receptors and are primarily involved in the renin-angiotensin-aldosterone system that regulates blood pressure. These are usually patients with added comorbidities, such as diabetes and hypertension, who have a weakened immune system.

The regions of Catalonia (Catalunya/Cataluña), Valencia, Murcia, the Canary Islands (Canarias) and the town of Ceuta have higher adjusted rates than the other regions. Conversely, the lowest rates are recorded in Cantabria and Castile and León (Castilla y León). When rates are analysed by sex, men are clearly seen to have higher rates than women in all regions, except in the Balearic Islands (Illes Balears), Ceuta and Melilla, being almost twice as high in several regions.

The Spanish Registry of Kidney Diseases was founded in 2006 as a result of merging the data provided by all regional registries. These consolidated data show a real difference in the prevalence of this pathology.

HIV-AIDS

HIV infection and AIDS diagnosis is not usually listed as a risk factor in most studies as such; immunodeficiency is. However, this term is very broad and difficult to define. So a pathology like VIH-AIDS, with a well-established information system and a clear impact on the immune system, especially cell-mediated immunity, was opted for in this study.

HIV/AIDS prevalence in Spain is low in general, yet it shows significant differences between regions. It mainly affects males. There is an increasing number of cases in the Balearic Islands (Illes Baleares), the Canary Islands (Canarias) and the Region of Valencia (Comunitat Valenciana) that are linked to tourism, which could be a reason for relaxing protection/prevention measures. The Region of Madrid (Comunidad de Madrid) also follows this pattern of prevalence. On the other hand, Catalonia (Catalunya/Cataluña) shows a very low prevalence even though it is also a region where tourism plays an important role.

Although the data are unadjusted for age and sex, it is very likely that these differences between regions are real, as the age group of people affected is more limited (young, young adults and adults) and the demographic differences between regions are somewhat smaller in these age groups than in the case of the elderly.

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{{ANETextoAsociado|titulo='''EPOC'''|contenido=[[Archivo:Espana_Prevalencia-declarada-de-EPOC-en-la-poblacion-mayor-de-15-anos_2017_mapa_17860_spa.jpg|left|thumb|300px|Mapa: Prevalencia declarada de EPOC en la población mayor de 15 años. 2017. España. [//centrodedescargas.cnig.es/CentroDescargas/busquedaRedirigida.do?ruta=PUBLICACION_CNIG_DATOS_VARIOS/aneTematico/Espana_Prevalencia-declarada-de-EPOC-en-la-poblacion-mayor-de-15-anos_2017_mapa_17860_spa.pdf PDF]. [//centrodedescargas.cnig.es/CentroDescargas/busquedaRedirigida.do?ruta=PUBLICACION_CNIG_DATOS_VARIOS/aneTematico/Espana_Prevalencia-declarada-de-EPOC-en-la-poblacion-mayor-de-15-anos_2017_mapa_17860_spa.zip Datos]. [//interactivo-atlasnacional.ign.es/index.php#c=indicator&i=r_121_t.r_121_t&s=Total&t=A02&view=map10 Versión interactiva. ]]] La enfermedad pulmonar obstructiva crónica (EPOC) no parece ser un factor predisponente a la infección por SARS-CoV-2, pero una vez que se desarrolla la enfermedad, se tiene un mayor riesgo de hospitalización, ingreso en unidades de cuidados intensivos (UCI) y letalidad. Por otro lado, la clínica respiratoria de la COVID puede en ocasiones confundirse con exacerbaciones de la EPOC, lo que podría retrasar el diagnóstico y condicionar la evolución clínica. El mecanismo fisiopatológico subyacente sería un incremento de expresión de los receptores ACE2 (al que se une el virus para penetrar en la célula) en el epitelio bronquial entre otros.