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[[File:Logo Monografía.jpg|left|thumb|300px|Map: Reportered of COPD in the population over 15 years of age. 2017. Spain [//centrodedescargas.cnig.es/CentroDescargas/busquedaRedirigida.do?ruta=PUBLICACION_CNIG_DATOS_VARIOS/aneTematico/Espana_Prevalencia-de-obesidad-en-la-poblacion-mayor-de-18-anos_2017_mapa_17861_spa.pdf PDF]. [//centrodedescargas.cnig.es/CentroDescargas/busquedaRedirigida.do?ruta=PUBLICACION_CNIG_DATOS_VARIOS/aneTematico/Espana_Prevalencia-de-obesidad-en-la-poblacion-mayor-de-18-anos_2017_mapa_17861_spa.zip Data]. [//interactivo-atlasnacional.ign.es/index.php#c=indicator&i=r_122_t.r_122_t&s=Total&t=A02&view=map10 Versión interactiva. ]]]

Chronic Obstructive Pulmonary Disease (COPD) does not appear to be a predisposing factor for SARS-CoV-2 infection. However, once infection occurs and the disease develops, there is an increased risk of hospital admission, admission to intensive care unit (ICU) and death. Furthermore, the respiratory symptoms of COVID-19 may sometimes be confused with COPD exacerbations, which may delay diagnosis and affect the clinical course. The underlying pathophysiological mechanism would be an increased expression of ACE2 receptors (to which the virus binds to penetrate the cell) in the bronchial epithelium, amongst others.

The SEMI-COVID-19 registry of the Spanish Society of Internal Medicine provides clinical data on patients from hospitals across the country, including a history of COPD in 7% of those patients.

The map shows clear differences in reported prevalence between territories. Galicia, Asturias, Extremadura, Aragón and Castile and León (Castilla y León) stand out, with prevalences of around 5%, compared to regions such as the Balearic Islands (Illes Balears) and the Canary Islands (Canarias), with less than 3%. In relation to gender, it is interesting to note that the prevalence in women is higher or equal to that of men in some regions even though COPD is associated with smoking.

There are two major limitations to the data shown. The first is that they are based on self-reported data, which may constitute a reporting bias. The second is that the data are not age- or sex-adjusted, so the differences shown in prevalence may be explained by a different population structure. COPD is an age-associated disease; the regions with the highest prevalence are those with a large elderly population.

[[File:Logo Monografía.jpg|left|thumb|300px|Map: Reportered prevalence of hypertension in the population over 15 years. 2017. Spain. [ PDF]. [/ Data]. [//interactivo-atlasnacional.ign.es/index.php#c=indicator&i=r_123_t.r_123_t&s=Total&t=A02&view=map10 Versión interactiva. ]]]

Hypertension is an important risk factor that has been discovered in 19% of patients with COVID-19 in Spain. The biological concept is based on its effect on the renin-angiotensin-aldosterone system and on angiotensin-converting enzyme 2 (ACE-2) overexpression.

Two facts stand out in the data shown: on the one hand, the reported prevalence shows figures of 20-25% in all regions, except for the Balearic Islands (Illes Balears) that registers around 10%; on the other hand, the similarity of figures between men and women, except in the cases of Navarre (Navarra) and Melilla. However, the interpretation of the data has the same limitations as in the case of COPD.

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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[[File:Logo Monografía.jpg|left|thumb|300px|Map: Prevalence of obesity in the population over 18 years of age. 2017. Spain. [ PDF]. [/ Data]. [//interactivo-atlasnacional.ign.es/index.php#c=indicator&i=r_123_t.r_123_t&s=Total&t=A02&view=map10 Versión interactiva. ]]]

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.

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.

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[[File:Logo Monografía.jpg|left|thumb|300px|Map: Reportered prevalence of diabetes in the population over 15 years. 2017. Spain. [ PDF]. [ Data]. [//interactivo-atlasnacional.ign.es/index.php#c=indicator&i=r_123_t.r_123_t&s=Total&t=A02&view=map10 Versión interactiva. ]]]

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.

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[[File:Logo Monografía.jpg|left|thumb|300px|Map: Reportered prevalence of hypertension in the population over 15 years. 2017. Spain. [ PDF]. [/ Data]. [//interactivo-atlasnacional.ign.es/index.php#c=indicator&i=r_123_t.r_123_t&s=Total&t=A02&view=map10 Versión interactiva. ]]]

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.

There are two clear patterns: one geographical and the other by sex. Castile and León (Castilla y León) and the Region of Valencia (Comunitat Valenciana) show a very high prevalence, around 14%. The data for Extremadura and Castile-La Mancha (Castilla-La Mancha) warrant a separate reading, with prevalences that are 30% lower than those in the regions with higher prevalence.

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.

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