Prevalence of self-reported diabetes and hypertension among users of primary health care services

The objective of this cross-sectional study was to estimate the prevalence of self-reported hypertension and diabetes among the users of primary health care services of Southeast Ribeirão Preto, State of São Paulo, Brazil, and to identify variables which may be associated with these chronic conditions. A stratified sample of 1,055 adult individuals was surveyed, with the resulting associations being examined by using log-binomial regression models and then expressed as prevalence ratios (PRs). The prevalence of self-reported hypertension among women was 20.2% (95%CI: 17.5-23.1) and among men was 29.0% (95%CI: 22.9-35.5), while the prevalence of self-reported diabetes among women was 6.9% (95%CI: 5.28.8) and among men was 12.2% (95% CI: 8.1-17.3). The prevalence of both conditions increases significantly with age. Crude and adjusted PRs indicate no association between socioeconomic status and the self-reported chronic conditions.


Introduction
Hypertension and diabetes are two chronic conditions that have high economic impact on the social and healthcare systems due their high prevalence and associated diseases.The average age of the world's population is increasing rapidly, which contributes to the rise in the prevalence of both conditions.
Diabetes is a chronic metabolic disorder characterized by hyperglycemia resulting in defects in the properties and secretion of insulin, or both (Rojo-Botello, García-Hernández, & Moreno-Fierros, 2012).There are two main types of diabetes.The type-1 diabetes, also called insulin dependent diabetes mellitus, is characterized by the destruction of insulin-producing beta cells in the pancreas.The type-2 diabetes, also called non-insulin dependent diabetes mellitus, is caused by a decreased sensitivity of target tissues to insulin.It is estimated that, by the year of 2030, the prevalence of diabetes in South and Central Americas will be 7.8% after age-standardization (Shaw, Sicree, & Zimmet, 2010).Hypertension is a common disorder of multifactorial origin in which blood pressure elevation is only one sign.It constitutes a major risk factor for events such as stroke, heart disease, and kidney failure.It is estimated that approximately one in four adults has hypertension and that more than 1.5 billion people worldwide will be affect in 2025 (Olsen et al., 2016).
Among the components recommended by the World Health Organization (WHO) to address hypertension, there are integrated programs at the primary healthcare level for control of the disease (World Health Organization [WHO], 2016).Therefore, effective treatments should be available at the primary healthcare level aiming to control hypertension and thus reduce the risk of complications.Studies on users of primary healthcare services are important to improve the general health in the community.
This observational cross-sectional study aimed to estimate the prevalence of self-reported hypertension and diabetes among users of primary healthcare services in Ribeirão Preto, Brazil, and to identify variables which may be associated with these chronic conditions.The present study differs from previously reported works in at least three ways.First, the information was collected through face-to-face interviews carried out at health care units.Second, it was focused on a specific population of users rather than general population.Third, there are a few articles describing the concurrent prevalence of self-reported diabetes and hypertension.

Material and methods
Ribeirão Preto is a city located in the northeastern region of the State of São Paulo, with a population of around 674 thousand inhabitants.The city has an economy based primarily on agricultural activities mostly related to sugar cane industry, with the local health care system being divided into five geographical areas with diverse demographic characteristics, namely, North, South, Central, East and West districts.It is estimated that 52% of the urban population of Ribeirão Preto have been exclusively using the public health care resources, whereas 80% use these services occasionally (Prefeitura Municipal de Ribeirão Preto, 2011).
The study design was based on a stratified sampling scheme in which 41 primary health care units were grouped according to geographical area and a local social vulnerability index (IPVS) regarding the areas of coverage.This index was proposed by the Brazilian State Data Analysis System Foundation (SEADE) as it rates geographical areas into six categories of social vulnerability (Schumann & Moura, 2015).Twelve strata and one health care unit from each stratum were randomly selected for the interviews.The sample size was determined by considering the mean number of monthly visits in each health care unit and the hypertension and diabetes prevalence in this population was estimated at 95% confidence level and absolute precision of 3% to estimate.This prevalence was set at 50% in each stratum to maximize the variance, which resulted in a minimum sample size of 1,055 individuals for this study.Data were collected from August 2015 to May 2016 through face-to-face interviews conducted by three trained interviewers from.The inclusion criteria were age of 18 years or older and user of the primary health care services of Ribeirão Preto.
People with self-reported hypertension were defined as those who responded "yes" to the question: "Have you ever heard from a doctor, at some moment in your life, that you have hypertension?"Persons with self-reported diabetes were identified in a similar manner.Socioeconomic status was assessed by using the classification proposed by the Brazilian Association of Market Research Institutions, which is based on accumulation of material goods and schooling of the household head.Possible ranks are A, B1, B2, C1, C2, D and E, with people from more privileged socioeconomic classes being labeled as A. Education level was ranked into five groups: insufficient school (including illiterates, people who never attended school or people who did not complete elementary school I), elementary school II (incomplete or complete), intermediate school (incomplete or complete), and higher education (incomplete or complete).The Alcohol Use Disorder Identification Test (AUDIT) was used to rank the pattern of alcohol use into four risk zones: (I) non-drinker, (II) non-hazardous, (III) hazardous and (IV) harmful drinking (Babor & Robaina, 2016).
Prevalence was estimated by using the exact method at 95% confidence interval (Fleiss, Levin, & Paik, 2013).Log-binomial regression models were fitted to the data (Chen, Shi, Qian, & Azen, 2014) and prevalence ratios (PRs) were used as measures of association between independent variables and each dependent variable (i.e.hypertension and diabetes).Inferences for PRs were based on 95% confidence intervals so that intervals not including 1 indicated that the respective variable is associated at a significance level of 0.05 (similar to P < 0.05).SAS 9.3 software was used for all statistical analyses.Research was conducted according to current ethical norms and the project was approved (protocol number 931.952) by the Research Ethics Committee of the Clinical Hospital, Ribeirão Preto Medical School, University of São Paulo (USP).

Results and discussion
The sample was composed of 841 (80%) women with mean age of 39.5 years (SD 14.9) and 214 (20%) men with mean age of 45.1 years (SD 15.3).The minimum age was 18 years old.The low frequency of men attending the health care units is a well-known phenomenon in Brazil and this has been discussed in a number of publications (Couto et al., 2010;Gomes, Nascimento & Araújo, 2007;Gomes et al., 2011).
The prevalence of self-reported hypertension and diabetes according to the characteristics of the respondents are showed in Tables 1 and 2, respectively.The prevalence of both conditions increases significantly with age.A higher prevalence of both conditions was observed among respondents with poor self-perception of health.No association between socioeconomic status and self-reported chronic conditions was detected according to crude and adjusted PRs.
Table 3 shows the concurrent prevalence rates of self-reported diabetes and hypertension according to characteristics of the respondents.A large increase in the prevalence was observed with ageing.Table 3 also shows higher prevalence among respondents with poor self-perception of health and ex-smokers.The strengths of the present study include the use of a sample composed by individuals who were personally interviewed.In this sense, important studies like the VIGITEL (Telephonebased Surveillance of Risk and Protective Factors for Chronic Diseases) study (Schmidt et al., 2009), have been based on a sample limited to adults interviewed at home by telephone.
The present study has shown a higher prevalence of self-reported hypertension among men (29.0%) than among women (20.2%), although this difference was no longer significant after adjustment for age group (Table 1).In a large study on self-reported hypertension in the Brazilian capitals (Andrade, Malta, Iser, Sampaio, & Moura, 2014), prevalence rates of 19.6% and 24.9% were found in men and women, respectively, in the city of São Paulo.Other study using data from the National Household Sample Survey (PNAD) (Muniz et al., 2012) estimated that in the South-eastern region of Brazil the prevalence of self-reported hypertension among men is 12.4% and among women is 16.5%.The prevalence rates estimated in the present study are closer to those reported in the National Health Survey (NHS) of 2013 (Malta, Santos, Perillo, & Szwarcwald, 2016), where blood pressure was measured by using a calibrated digital device.Considering the adult population of the state of São Paulo, the prevalence of hypertension was 27.6% among men and 21.3% among women.In a previous study (Torquato et al., 2003), the prevalence of diabetes in the urban population aged 30-69 years was estimated based on WHO criteria, where previously-diagnosed individuals and those with fasting or two-hour capillary glycemia higher than 200 mg dL -1 were considered to be diabetics.It was founded that men and women have similar rates of diabetes (12.0 and 12.1%, respectively).By using this same age group, the present study found a prevalence of self-reported diabetes of 14.4% among men and of 8.6% among women.Considering all the adult individuals, the prevalence of self-reported diabetes reported in the present study was 6.9% among women.This value is very close to that found in the NHS (Iser et al., 2015), showing a prevalence of self-reported diabetes of 7.0% for the country's female population.However, the prevalence of self-reported diabetes among men obtained in the present study is higher than that reported in NHS (Iser et al., 2015).
In the present study, the concurrent prevalence rates of self-reported diabetes and hypertension was estimated as 5.4%.This prevalence is higher than that reported in a previous study based on PNAD database (3.3% for the whole country and 3.9% for the Southeastern region) (Freitas & Garcia, 2012).
The main limitation of the presented study concerns the validity of self-reported hypertension and diabetes.Three Brazilian large population-based studies showed sensitivities of 72.1, 84.3 and 71.1% for self-reported hypertension (Lima-Costa, Peixoto, & Firmo, 2004;Chrestani, Santos & Matijasevich, 2009;Lima-Costa, Peixoto, Firmo, & Uchoa, 2007) and specificities of 86.4,87.5 and 80.5%, respectively.The NHANES III Survey showed a sensitivity of 71% and a specificity of 90% (Vargas, Burt, Gillum, & Pamuk, 1997).On the other hand, there are a few studies on the validity of self-reported diabetes in Brazilian populations.Although studies conducted outside Brazil have indicated that self-report of diabetes shows little disagreement with other sources of information (Jackson et al., 2014).A Brazilian study showed a low sensitivity (57.1%), suggesting that self-reported diabetes may not be suitable as an indicator of disease prevalence for the Brazilian population (Lima-Costa et al., 2004).Apart from the people's poor knowledge of their own health status, it is known that diabetes and hypertension rarely cause symptoms in the early stages and many people go undiagnosed (WHO, 2016).Therefore, in any case, estimates of self-reported hypertension and diabetes prevalence are always subject to underreporting.Despite these problems, the values of prevalence obtained in this study are satisfactorily close to those reported in works using objective criteria to diagnose hypertension (Malta et al., 2016) and diabetes (Torquato et al., 2003).This demonstrates the utility of the results to describe the frequency of these health conditions among users of primary health care services in Ribeirão Preto.
Another important limitation of this study is its cross-sectional design and thus caution should be taken in interpreting the associations showed in Tables 1 and 2. As the effect of exposure time is not considered here, more detailed studies are needed to address the issues of time-lag and reporting biases -the major problems in interpreting these findings.

Conclusion
In conclusion, knowledge on the prevalence of diabetes and hypertension in Brazil is essential for supporting prevention and control measures that will contribute to reducing the impact of cardiovascular diseases at population level, and the present study can be considered a small contribution in this direction.
(a) PR adjusted for sex and age.* 95% CI does not cover the value of 1, suggesting a significant effect (similar to p < 0.05).
(a) PR adjusted for sex and age.* 95% CI does not cover the value of 1, suggesting a significant effect (similar to p < 0.05).

Table 3 .
Crude and age-and-sex adjusted prevalence ratios (PR) for hypertension and diabetes (n = 1,055).