EXERCISE , BLOOD PRESSURE AND MORTALITY : FINDINGS OF EIGHT YEARS OF FOLLOW-UP EXERCÍCIO

Introducao: Nas ultimas decadas, habitos pouco saudaveis, como baixos niveis de atividade fisica e ma alimentacao, tem aumentado. Consequentemente, a prevalencia de doencas cardiovasculares e de mortalidade aumentou significativamente entre adultos. Entretanto, e sabido que a pratica regular de exercicios fisicos ajuda a melhorar os desfechos de saude. Assim sendo, o objetivo deste estudo foi analisar os efeitos de oito anos de participacao regular em um programa de exercicios sobre a pressao arterial e a mortalidade no sistema brasileiro de saude publica. Metodos: A amostra foi composta por 34 participantes com hipertensao e/ou diabetes tipo II, que foram acompanhados por oito anos. Eles foram pareados por idade, indice de massa corporal e doenca cronica em dois grupos: exercicio e controle. Durante o periodo de acompanhamento, os registros medicos foram usados para avaliar a pressao arterial sistolica e diastolica, bem como o numero de consultas medicas e a ocorrencia de obitos. Resultados: No periodo de acompanhamento, ocorreram cinco obitos no grupo controle e nenhum no grupo exercicio. A analise de Kaplan-Meier identificou mortalidade 29,4% menor entre os participantes ativos (teste exato de Fisher com p = 0,044). A quantidade de consultas medicas e pressao arterial diastolica foram significantemente menores para os participantes ativos. Conclusao: Apos acompanhamento de oito anos, participantes do grupo exercicio tiveram menor numero de consultas medicas, melhor controle da pressao arterial e menor ocorrencia de mortes.


INTRODUCTION
During the last few decades, participation in physical activity has decreased and unhealthy dietary habits have increased.Over the same period of time, the prevalence of cardiovascular diseases and mortality has increased significantly among adults 1 .The development of drugs to treat these cardiovascular complications has improved both the treatment and quality of life of patients.However, non-pharmacological interventions (such as physical activity) should be the first approach to treating cardiovascular complications 2 .
Previous studies have identified a lower prevalence of cardiovascular complications and mortality among physically active people 3,4 .Moreover, the practice of physical activity both increases life expectancy 5 and decreases healthcare expenditures 6,7 .For developing nations, however, no longitudinal data exist concerning the effects of physical activity on medical consultations and mortality in patients who receive care from the public healthcare system.
The purpose of this study was to analyze the effects of eight years of regular physical exercise on blood pressure and mortality among patients of the Brazilian National Health System.

Sample
The study covered the period from 2003 to 2010 in Bauru city (~360,000 inhabitants), a medium-sized Brazilian city, located at middle part of Sao Paulo State, the richest state of the Brazilian federation.
In the city of Bauru, the primary care of the Brazilian National Health System is organized in 17 primary health care units (small units spread over different regions of the city, which are devoted to: medical consultations [different medical specialties], low complexity medical procedures, medicine delivery and vaccines) and this study was conducted with patients by one of them (BHU "Otávio Rasi").
The pair-matched sample of 34 patients was randomly selected to match sex, chronological age, body mass index status and chronic disease (2 paired diabetic patients; 22 paired hypertensive patients and 10 paired patients with both diseases), then assigned into exercise group (EG, n=17) and control group (CG, n=17) and followed up for eight years.
The exercise program occurred within the university and was led by undergraduate students under supervision.It consisted in 40 minutes of walking at moderate intensity (40-65% of maximum oxygen uptake) and 20-25 minutes of strength training using dumbbells three times per week.
The study was approved by Ethics Committee of the Municipal Health Department of Bauru/SP (Document from March 22 nd 2003) and all participants signed the written consent form.
Patients' medical records were used to compute the dependent variables, including systolic (SBP) and diastolic (DBP) blood pressure and number of nursing and medical (e.g.dentist, gynecologist, endocrinologist, cardiologist, obstetrician, general practitioner and psychiatrist) consultations per year.The occurrence of deaths among patients was obtained through medical records and family report.

Statistical analysis
Data presented non-parametric distribution and, therefore, the Friedman test compared numerical values through follow up.Numerical variables were presented as median and interquartile range values.General characteristics at baseline were compared using the Mann-Whitnney's test.Fisher's exact test and Kaplan-Meier analysis were used to treat the categorical variables.BioEstat (release 5.0) processed all analyses, and statistical significance was set at p< 0.05.

RESULTS
Women represented 66.5% of the sample.The average age of the sample was 70.7 years old ( ± 10.3).There were no differences in baseline values between the EG and CG (Table 1).In the EG, the Friedman test identified differences in SBP (p= 0.024) and DBP (p= 0.001).Compared to baseline values, DBP in EG increased in third and fourth years of follow up, but decreased significantly in the eighth year (p= 0.044).SBP did not differ from the baseline (Figure 1).
Figure 2 is a table of survival, in which the Kaplan-Meier test shows the probability of remaining alive during the follow-up.It was observed that the CG showed a reduction of 29.4% in their probability of survival over follow-up analysis.Similarly, a significant association was found between mortality and exercise practice (p = 0.044).

DISCUSSION
This prospective study followed hypertensive and diabetic patients for eight years.Those who regularly engaged in physical exercise had decreased mortality, DBP and quantity of medical consultations.
Similar to our findings, Farrell and colleagues 8 found that men who engaged in moderate and vigorous physical exercise had a lower mortality risk than sedentary men after 19 years of follow-up.Similar results have been observed among elderly 9 .Both our findings and current scientific literature have shown that regular exercise protects against early mortality, even among elderly with chronic diseases.However, future studies are needed to identify the ideal type and amount of exercise for preventing mortality and complications associated with chronic diseases.Among adults, a physically active lifestyle has been associated with a lower incidence of arterial hypertension 10,11 .In a study that included 40 years of follow-up, long-term practice of physical activity had a protective effect on incidence of cardiovascular disease and all-cause and CVD-attributable mortality in men, compared with long-term physical inactivity 3 .Among the hypertensive patients in the present study, blood pressure was reduced after eight years of regular exercise.A number of studies have reported that exercise reduces blood pressure in both hypertensive and normotensive subjects [12][13][14] .Although the mechanisms by which regular exercise reduces blood pressure are not completely clear [15][16][17] , the benefits of physical activity may accrue through reduction of other cardiovascular risk factors, such as improved glucose tolerance 18 or lower BMI and visceral fat 19 , resulting in a lower occurrence of comorbidities associated with hypertension 20 .In addition, long-term regular physical activity preserves cardiac compliance 21 , endothelial regulation of smooth muscle tone and other aspects of vascular wall structure/function 22 , workload and cardiac performance 23 .Additionally, aerobic exercise training may significantly lower blood pressure in older hypertensive individuals, improving endothelial function and vascular tone 24 .
In the present study the number of medical consultations was reduced among those in the exercise group.Few studies have examined the relationship between healthcare costs and regular exercise.Recently, studies have identified reductions in expenditures related to medical consultations and the use of medicine among hypertensive 25 and diabetic 7,26 patients of the Brazilian National Health System, showing that people who exercise regularly are sick less often, therefore they don't go to the medical consultations as much.Also, the positive effects of regular physical activity on cognitive function, mood disorders and sleep quality, could improve the wellness of the individual 27 and, therefore, improve their self-perception of health, which would reduce the number of medical consultations.
Recently, a systematic review 28 evaluating the effects of physical activity on mortality in hypertensive patients between 1985 to 2012 reported that cardiovascular and / or all-cause mortality were inversely related to increased physical activity.The review noted, however, the lack of research to assess the effects of regular physical exercise on mortality and control of blood pressure in hypertensive patients over a follow-up period, which was the focus of the present study.
Some limitations of the study must be considered when interpreting the results.The small number of individuals in the sample and the fact that we did not assess confounding factors such as smoking, genetic background and other chronic diseases as heart attack, stroke and cancer that could have influenced the observed associations.

CONCLUSIONS
In summary, the longitudinal effects of regular exercise in diabetic and hypertensive patients were to reduce the number of healthcare services used and the mortality rate, in addition to better blood pressure control.

Table 1 .
General characteristics of the patients at baseline study(Brazil, 2003).