Researchers establish patterns of association among chronic diseases

In analyzing data from interviews conducted with 5,037 residents of the São Paulo Metropolitan Region, Brazilian researchers identify how factors such as age and socioeconomic status influence patterns of multimorbidity among chronic diseases.

By Karina Toledo

Agência FAPESP – In analyzing data from interviews conducted with 5,037 residents of the São Paulo Metropolitan Region, researchers from the University of São Paulo Medical School (FMUSP) have identified which individual factors, including gender, age, socioeconomic status and place of residence, influence patterns of multimorbidity – a term that refers to the co-occurrence of two or more chronic medical conditions in one person.

According to the findings, the co-occurrence of migraines and other painful conditions, episodes of anxiety, depression and insomnia were nearly twice as common among women. An association between arthritis and metabolic diseases such as cardiovascular disease and diabetes was found more frequently among the elderly and among residents of neighborhoods with greater income inequality.

The concomitant association of problems related to drugs, alcohol and tobacco was more common among young adults, males and those with greater economic power. In terms of diseases including cancer and neurological conditions such as Alzheimer’s disease, however, there was no relationship between the individual and contextual factors investigated.

“Our findings, as well as those from international studies, indicate that people with two or more chronic diseases are at an increased risk of developing other associated chronic conditions. The more advanced one’s age, and the lower one’s socioeconomic level, the greater is the risk, and this ends up creating clusters of physical and mental morbidity among the population,” said Wang Yuan Pang, a researcher at the Institute of Psychiatry at the Hospital das Clínicas (HC) of the FMUSP and study coordinator, along with Laura Helena Andrade, also of FMUSP.

Pang presented the findings on April 8 during the international event known as the World Health Summit – Regional Meeting Latin America, and they will be published in a special edition of the journal The Lancet, which is scheduled to be released in October in Berlin, Germany.

The analysis is an extension of the São Paulo Megacity Mental Health Survey (read more about it at: http://agencia.fapesp.br/en/15329) completed in 2009 within the scope of the thematic project entitled “Epidemiological study of psychiatric disorders in the São Paulo Metropolitan Region: prevalence, risk factors, and social and economic burden,” funded by FAPESP and led by Andrade.

The interviews were conducted between 2005 and 2007 with a representative sample of the population of the São Paulo Metropolitan Region over age 18 years. The initial objective was to estimate the prevalence of mental disorders in a highly urbanized area. The number found was near 30% – the highest number recorded among the 24 countries included in the World Health Organization’s (WHO’s) World Mental Health Survey.

Anxiety disorders were the most commonly found mental disorder and affected 19.9% of those interviewed. Next were mood disorders (11%), impulse control disorders (4.3%) and problems related to substance abuse (3.6%). Nearly 10% of the cases were considered serious. Of these, only 30% had access to treatment.

“Our questionnaire included a section about chronic diseases. We asked if at any time the person had received a doctor’s diagnosis for conditions such as cardiovascular problems, hypertension or diabetes, and we used previously validated scales to assess conditions such as migraines and insomnia,” Andrade said.

São Paulo Megacity

According to Pang, the São Paulo Megacity database analysis enabled the group to divide the 14 chronic conditions mentioned by the interviewees into four patterns of diseases that were strongly correlated, or to multimorbidity: one pattern is made up of painful diseases, anxiety and depression; a second consists of metabolic diseases and arthritis; a third is related to substance abuse; and a fourth, more biological pattern, includes cancer and neurological conditions.

“We then decided to investigate what determined a particular pattern of disease concentration. We used a statistical technique called factor analysis to do this. We established a regression coefficient to use as an indicator and tested various models of multi-level analysis to assess how much each of the individual factors and contexts influenced each of the four patterns of multimorbidity,” said Pang.

These findings also indicated that cardiovascular disease, anxiety disorders and depression were the diseases that were the most highly associated with other chronic conditions. The researchers estimate that they have the greatest impact on the quality of life of those affected. These findings confirm the recent information found in the Global Burden of Disease Study 2010 for Brazil.

According to the researchers, the data identify the importance of reformulating medical treatment to offer patients more integrated treatment.

“Medicine in Brazil is very specialized. Cardiologists take care of hearts, pulmonologists take care of lungs, etc. But in reality, cardiologists should also be concerned about depression, anxiety and pain because these conditions are often associated,” opined Pang.

“Mental disorders are very common and often occur together with other chronic diseases. Psychiatry therefore needs to be included in planning strategies for treatment and prevention,” Andrade emphasized.

The study also received funding from FAPESP through the recently concluded project “Identification of subgroups of alcohol users and related factors in the São Paulo Metropolitan Area: gender differences, sociodemographic characteristics and psychiatric comorbidities.”