In this cohort study of over 3.2 million adults, we found that overall CVD incidence increased while HTN and T2DM incidences decreased in both women and men from 2009–2018, although there were slight differences by age group and specific time period. For example, CVD incidence decreased in the 70 + age group, while T2DM incidence increased in the 40–54 age group. HTN incidence increased from 2009–2013, before dropping until 2018. When stratifying by SES, higher incidence levels were observed in the most deprived areas, especially in the youngest two age groups, despite CVD, HTN, and T2DM trends mirroring the overall trends.
Our study found increasing CVD incidence in the 40–54 and 55–69 year age groups, but decreasing CVD incidence in the 70 + year age group. Past studies have mostly identified decreasing CVD incidence in most high-income countries during the late 20th and early 21st centuries (5). Moreover, studies on global (21) and European (22) CVD mortality both found that CVD mortality rates have decreased in past decades in adults. Within the context of specific European countries, a study of incident myocardial infarction in the United Kingdom (UK) found that hospitalization events have been increasing in recent years (23). Moreover, a study from Girona, Spain from 2005 found an increase in heart attack incidence in adults (24). However, the results of these studies have not been stratified by age group and, thus, it is difficult to compare directly with our results.
Few studies have considered differences in CVD trends across multiple age groups in the same study. A study performed in England and Wales found that rates of coronary heart disease increased among the youngest age group of men (35–44 years), despite decreasing steadily among the oldest age group (25). Furthermore, a review of CVD epidemiology in young adults found that, in contrast to older adults, trends in CVD incidence in young adults have been increasing or plateauing in recent decades (26). These results, which are congruent with the findings of our study, highlight the importance of considering potential differences by age when understanding disease trends, as all population subgroups may not exhibit the same trends. Differences in CVD incidence trends by age group may be explained by the fact that in many developed countries, rates of important CVD risk factors such as substance abuse (27, 28), physical inactivity (29), and obesity (30) are increasing among adolescents and young adults. Moreover, these risk factors do not affect all population subgroups equally, with low SES being associated with higher rates of substance abuse (31, 32), physical inactivity (32), and obesity (33). As a result, we would expect higher CVD incidence among individuals of a low SES, which we discuss in more detail below.
Our study found a decrease in HTN incidence after 2013 across all age and sex groups. Few studies to our knowledge have looked at longitudinal time trends in HTN incidence. Our results are consistent with a study of HTN incidence trends from 1995–2015 in the UK, which also found decreasing HTN incidence in adults after a peak in 2007, due in part to greater control and prevention efforts (34). Our results are also consistent with past multi-country studies that have studied HTN prevalence. For example, a worldwide study on trends in hypertension prevalence from 1990–2019 showed that, among high-income countries, HTN prevalence has declined as health systems have achieved high control rates during recent decades (35). Both the data from Spain as well as from other comparable European countries all follow the same decreasing trends (35). Given that HTN prevalence is decreasing, we would expect incidence rates to mirror this decrease as well.
We found a marked decrease in HTN incidence starting in the year 2013. We hypothesize this may be due to the implementation of the electronic prescription system and a plan for HTN control in Catalonia around a similar time. In 2013, the Catalan Health Institute (ICS) officially implemented an electronic prescription system. This system allowed primary care physicians to upload and edit prescriptions for HTN medications to the online system, making it easier to accurately record patients with an incident HTN diagnosis (36). Secondly, in 2011 a plan was implemented by the ICS to better control HTN within the resident population of Catalonia (37). This plan included specific objectives for HTN prevention, with economic benefits for healthcare clinics and providers that met the objectives of the plan (37). This plan and its associated benefits may incentivized HTN prevention and control around 2011 when it was implemented, perhaps leading to a decrease in HTN incidence in subsequent years. Given that both of these changes took place around the same time frame, we hypothesize that their combination may explain the HTN incidence trends observed by our study.
Our study found that T2DM incidence decreased in both the 55–69 and 70 + year age groups, while increasing in the 40–54 year age group. Past studies have found that T2DM incidence is decreasing in a majority of global adult populations during recent decades (38), especially among high income countries (7). A previous study found that T2DM prevalence and incidence was increasing in Europe between the years 1995–1999, including in Spain (39), a trend that reversed both at the European and global levels around 2006 (38). There are few studies on T2DM incidence trends in Spain in recent years, though a past study found that mortality rates for T2DM fell markedly between the years 1998–2013 (40). However, studies conducted within other European countries show varying findings. For example, a study in Portugal found increasing T2DM incidence, especially among older age groups (41), though another study carried out in the UK found decreasing T2DM incidence in recent years (42). Thus, it is important to study T2DM incidence trends by varying populations to have an updated understanding of the situation of each specific population.
There have been few studies to consider trends in T2DM incidence by age group, despite evidence of differences in T2DM prevalence by age group (43). A study performed among a Canadian adult cohort found that T2DM incidence increased at a much greater rate in adults between 20–49 years, compared to adults older than 50 years (44). Similarly, a study of T2DM incidence trends in US American adults found a greater increase in T2DM incidence between 1980–2012 among adults aged 20–44 years, compared to adults aged 45–64 years (45). These differences by age group may be due to a greater increase in obesity prevalence in younger adults compared to older adults, both within Spain (30) as well as globally (46, 47), given that overweight and obesity are among the greatest risk factors for T2DM (48). Although a direct link between obesity and T2DM cannot be established with our study alone, the trends in T2DM incidence found by our study coincide with the increase in obesity in Spain (49, 50). Furthermore, low SES is associated with higher levels of physical inactivity (32) and obesity (33) and we would therefore expect disproportionate T2DM incidence across SES, as we discuss in more detail below.
Based on our results alone, it is difficult to assess whether incidence trends in HTN and T2DM are truly decreasing or if our results highlight a potential deficiency in HTN and T2DM prevention and control. Uncontrolled HTN (51) and T2DM (52, 53) lead to higher CVD incidence in the long term given that they are main risk factors for CVD. Therefore, if prevention and early detection of HTN and T2DM are not effective, patients may never receive a HTN or T2DM diagnosis but may be diagnosed directly with CVD in the long run as a result of not having their HTN and/or T2DM effectively prevented, diagnosed, or controlled. In this scenario, we would expect to see decreases in HTN and T2DM incidences paired with an increase in CVD incidence, as is signaled by our results.
Our study identified higher incidences rates of CVD, HTN, and T2DM in the most deprived areas, despite there being similar trends in incidence as in the least deprived areas. CVD, HTN, and T2DM incidence was especially higher in the 40–54 and 55–69 age groups in both sexes in the most deprived areas compared to the least. This suggests that, compared to individuals from less deprived areas, individuals residing in more deprived areas may be more likely to be diagnosed with CVD, HTN, or T2DM at a younger age. It is well documented that individuals of a low SES are at a higher risk of CVD (54), HTN (9), and T2DM (55, 56) and have a reduced life expectancy and higher risk of premature mortality (57, 58) than individuals of a higher SES. Past studies have also looked at the effect that low SES has on individual health behaviors such as smoking (59) and their harmful effects on health. However, it is important to also take into account the structural factors that impact individual health and individuals’ abilities to be healthy and take care of themselves. For example, low SES and education levels influence food behaviors (60), physical activity patterns and abilities (61), and access to preventative healthcare (62), all of which influence CVD, HTN, and T2DM risk. Therefore, though individuals of a low SES may understand the components of a healthy lifestyle, they may lack the economic conditions and resources to attain it. This in turn leads to higher risk and rates of illness, comorbidity, and premature mortality.
Inequalities in CVD, HTN, and T2DM incidence may persist due in part to the fact that there have not been equitable reductions in risk factors for these conditions across all social classes (63). Our results add to the growing body of literature which highlights the importance of tailoring interventions to the needs of specific populations, such as by social class, age group, or geographical location. Interventions that do not take population subgroups into account may improve overall trends for the general population, but may not be effective in reducing health inequalities (64). Health inequities can be combated through the creation of equitable health policies that are adapted to meet the needs of vulnerable groups and which enable changes in the health service structure to provide sufficient resources to all populations.
Strengths and limitations
The main strengths of our study are its large, representative sample size and the availability of longitudinal data. Most epidemiological studies that have been performed to this date that have considered CVD, HTN, and T2DM trends have been cross-sectional and, thus, have mainly focused on prevalence. In addition to providing longitudinal data, SIDIAP is known to contain a large, highly representative sample of the population living in Catalonia in terms of age, sex, and geographic distributions, lending external validity to our results (18).
However, our study also has some limitations that should be considered when interpreting the results. First, SIDIAP does not include data from health information registered by primary healthcare centers that are not associated with the ICS. Moreover, our definitions of CVD, HTN, and T2DM only took into account diagnostic codes recorded in SIDIAP and not prescriptions or lab reports, leading to a possible underdiagnosis of cases. By nature of being an EHR dataset, SIDIAP is not explicitly designed for calculations of population disease incidence, as the population included in the dataset is not a random population sample, but rather a sample of public healthcare users. However, bias that may be reflected in the capture and recording of outcomes is likely systematic. Finally, our study used the MEDEA index of deprivation, which is an ecological measure based on data from the 2001 census, given that we did not have individual-level data on SES. Additionally, the MEDEA is only calculated for urban areas, and, therefore, we were unable to include individuals who reside in rural areas in our study of trends by SES.