BACKGROUND Chronic Back Pain (CBP) may not be potentially fatal, but - - PDF document

The complete version of this paper is available in the Cadernos de Saúde Pública and was accepted for publication on July 13, 2017 under the title: (CSP_0128 / 17) "Prevalence, associated factors and related limitations in chronic back problems among adults and elderly in Brazil ". ______________________________________________________________ Epidemiology of Chronic Back Pain in Brazil: prevalence, life course, risk factors and activities of daily life limitations.

BACKGROUND Chronic Back Pain (CBP) may not be potentially fatal, but it is an important public health problem1,2,3. The CBP is highly prevalent, one of the main reasons for medical consultation4, responsible for serious losses of quality of life, high suffering and social and personal expenses. As the 2010 Disease Burden study, conducted with 118 surveys and 792 estimates from 47 countries reveals, the CBP is the leading cause of years lost due to disability5. In Brazil, CBP is also one of the most frequent chronic diseases in the population, with a prevalence of 18.5% in adults aged 18 years or over (95% CI: 17.8-19.1), according to data from the National Survey of Health (PNS) 20136. Knowing the life cycle of the disease, by age groups and generations, its intensity and impact on the quality of life, provide fundamental inputs for the prevention of spinal problems in the population7. However, although a few studies investigating the determinants of back pain and its impact on daily life activities have been conducted in developing countries, the literature is sparse compared with developed countries2. In Brazil, research is still not available in this perspective due, mainly, to the lack of population data on the limitations and restrictions of daily activities caused by the CBP. The Brazilian National Health Survey (NHS) that took place in 2013 is the first nationally representative survey to address this issue. Because of the major epidemiological and demographic transitions occurring in emerging economies in all regions of the world, there is now an urgent need to gather accurate comparable epidemiological data on back pain in older adult populations in developing countries. This work intends to contribute to this effort. A systematic review study, centered on this perspective, shows that, although prevalence increases with age, the relationship is not linear and stabilizes at around 60

• years8. Sex, age, occupation and obesity are factors related to the prevalence of CBP in

the literature 4, 9, 10, 11. The objectives of this study are to measure the prevalence of back pain in Brazil; identify risk factors and determinants associated with back pain, and describe association between back pain and disability in adults aged 60 years and older. METHODS:

Standardized national data collected from adults (18 years and older) participating in the Brazilian National Health Survey (NHS), 2013, were analyzed. The NHS is a household- based survey with a complex sampling design representative of the population of Brazil, Major Regions, UF`s, metropolitan regions and capitals12, in which the central objective is to characterize their health and lifestyle situation, besides collecting information on health care, access and health services. We analyzed the severity and characteristics of Chronic Back Pain (CBP) through prevalence and level of limitation. We measured socioeconomic inequalities and risk factors with a multivariate logistic regression, in a life course perspective, with the presence of CBP as the dependent variable. The independent variables were sex, age, educational level, household location, race/color, SRH, associated chronic diseases, BMI and physical activity. For each independent variable, the Odds Ratio (OR) with its respective 95% confidence intervals was calculated from the adjusted logistic models. Since it was a complex sampling design with more than one selection stage, all analyzes were performed using the ComplexSample module of the SPSS 21 statistical package. RESULTS: The prevalence of CBP was 18.5 (95% CI: 17.8-19.1), being higher for women and increasing with the age, reaching 28.1% (95% CI: 26.6-29.7) at the age of 60. CBP causes limitations in ADL in 67% of people, being 32.6% of low severity, 18.3% moderate and 16.4% intense. From the age of 50, 70% of CBP sufferers have some limitation and about 20% suffer from severe ADL limitations. The limitations gradually increase with age, stabilizing around the age of 50. Women had a higher risk of CCP than men (OR = 1.24, 95% CI: 1.14-1.35), with more disadvantages in the young to adult life stage (OR = 1.33, 95% CI: 1.20- 1.48). The lower educational level has a significant relationship with the CBP. People who have never attended school or with incomplete primary school are more likely to have CBPs in all age groups than those with college education or higher. Rural residents were 14% more likely to have CBP when compared to urban residents (OR = 1.14 95% CI: 1.01- 1.29). Race/color showed no significant association with CPB. SRH status has a high association with PCC. People with bad and very bad avaliation have four times more CBP (4.98 CI95%: 4.11-6.04) than those with very good SRH. With regular SRH the PCC is 3 times higher (OR 3.10 95% CI: 2.61-3.68). The effect of SRH

• n CBP decreases with age.

Several chronic diseases are associated with the presence of CBP. Arthritis is the most associated disease with CBP, presenting a three times higher risk for those who have it (OR = 2.78, 95% CI: 2.45-3.15), depression presents twice as much (OR = 2.0% CI 95% : 1.77-2.25). Chronic heart disease increases the chance of having CBP by 30% (OR 1.31 95% CI: 1.09-1.58), and the risk increases between 18 and 49 years (OR 1.61 95% CI: 1 , 13-2, 28). Having high blood pressure increases the risk of CBP by 14% in the general population (OR 1.14 95% CI: 1.03-1.27) and in 34% in the age range between 18 and 49 years (OR 1.34 95% CI: 1.15-1.57). Having asthma also increases the chance of having PCC, especially among the elderly. Having diabetes proved to be protective for the population and almost all age groups except 50-59 years.

BMI did not show a significant relation to the general population. By age group, it is

• bserved that for those 18 to 49 years of age, being overweight is a risk condition

compared to normal weight (OR = 1.25, 95% CI: 1.09-1.44). Obesity was a protective factor (OR = 0.74, 95% CI: 0.56-0.97). Being physically active did not prove to be significant for any of the age groups.

DISCUSSION The prevalence of CBP observed (18.5%) indicates that about 25 million people aged 18 years and older have the problem. This result is consistent with that found in the meta- analysis of Hoy et al. (2012)13 who considered 165 studies from 54 countries: the median prevalence of CBP was 19.4% and the mean was 18.1%. It is worth emphasizing the challenge of comparing the prevalence of CBP, mainly due to the methodological heterogeneity between the studies and the difficulties of obtaining valid population estimates. The analysis of the life cycle of the CBP, from 18 years to old age, showed a trend similar to that of other studies2,14: the prevalence of CBP increases rapidly to the stage of young to adult (around 6% at 18 years and 12% at age 30) and stabilizes after age 50. This may be due to cognitive impairment, increased pain tolerance and increased comorbidities could explain this stability in the old age. The severity of CBP also increases with age. In Brazil, from the age of 50, 70% of PCC sufferers suffered from some limitation. The intense or very intense limitations of the daily life activities increased from 2.8% at 18 years to 20.2% at 75 years. This result is in agreement with the results pointed out by the study of Load of the Disease7 that shows the CBP as one of the main problems that generate losses in quality life years. This study confirms the association between the presence of CBP and demographic, socioeconomic, behavioral and health conditions, with poor health status, comorbidities (arthritis, depression and asthma) and low schooling the main risk factors As already pointed out in several international studies that took place in high income countries

1,3,15,16.

Educational level is used as a strong predictor of CBP prevalence3,16 because it is a proxy variable of socioeconomic conditions during the life cycle. In Brazil, it was found that, controlling for several factors, uneducated people are 38% more likely to have PCC. Differences in work characteristics may explain a substantial part of this association. SRH is used a good indicator of quality of life and morbidity, and an important predictor

• f subsequent mortality, which has gained considerable interest in research over the last

three decade. There was a high correlation between the poor or very poor perception of health status and the occurrence of CBP. It is worth noting that with the advancement of age the association between bad ASS and the occurrence of CCP loses force.

The high prevalence and impact on living conditions reveal the need for epidemiological studies on CBP. Results suggest that promotion and prevention

• f CBP should be intensified, especially before the age of 50, considering the

country's marked aging of the population.

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