Artigos

Conteúdo (article):

FATORES ASSOCIADOS À MÁ QUALIDADE DO SONO EM BRASILEIROS MAIS VELHOS: UMA ANÁLISE TRANSVERSAL DO ELSI-BRASIL

FACTORS ASSOCIATED WITH POOR SLEEP QUALITY IN OLDER BRAZILIANS: A CROSS-SECTIONAL ANALYSIS OF ELSI-BRAZIL

Ricardo Rodrigues Pereira; instituição: Faculdade Ciências Médicas de Minas Gerais; e-mail: rodriguesrp.ricardo@gmail.com; orcid: 0009-0000-6957-3198
Murilo Reis Sampaio; instituição: Faculdade Ciências Médicas de Minas Gerais; e-mail: muriloreissampaio@terra.com.br; orcid: 0009-0007-1701-2015
Bruno Porto Pessoa; instituição: Faculdade Ciências Médicas de Minas Gerais; e-mail: bruno.pessoa@cienciasmedicasmg.edu.br; orcid: 0000-0002-4212-519x

RESUMO

Objetivo: Identificar a prevalência e fatores associados a má qualidade do sono autorreferida em adultos e idosos brasileiros com 50 anos ou mais. Métodos: Estudo transversal com participantes do Estudo Longitudinal da Saúde dos Idosos Brasileiros (2019-2021). Foram incluídos 9849 participantes com idade maior ou igual a 50 anos com informações completas para as variáveis de interesse. Qualidade do sono autorreferida foi a variável de desfecho. As variáveis independentes compreenderam indicadores sociodemográficos, comportamentais e condições de saúde. Foi realizada regressão de Poisson para estimativa das razões de prevalência (RP) e respectivos intervalos de 95% de confiança (IC95%). Resultados: A prevalência de má qualidade do sono foi de 15.6%. Foram observadas associações significativas entre o desfecho e sexo masculino (RP = 0.70; IC95%: 0.61 - 0.81), avaliar a saúde como boa (RP = 0.49; IC95%: 0.40 - 0.60) e residir na região sul (RP = 0.68; IC95%: 0.49 – 0.94), número de doenças crônicas (2.52; IC95%: 1.97 – 3.24, para os com duas ou mais) e avaliar a memória como ruim (RP = 1.30; IC95%: 1.12 – 1.51). Conclusão: A má qualidade do sono em adultos mais velhos no Brasil foi associada com diversos fatores, incluindo o sexo feminino, percepção negativa da saúde e da memória, consumo excessivo de álcool e a presença de múltiplas condições crônicas.

Palavras-chave: Qualidade do Sono;Prevalência; Idoso; Envelhecimento.

 
ABSTRACT

Objective: To identify the prevalence and main factors associated with self-reported poor sleep quality in Brazilian adults aged 50 and older. Methods: A cross-sectional study with participants from the Brazilian Longitudinal Study of Aging (2019-2021). A total of 9,849 participants, aged 50 and older, with complete information for the variables of interest were included. Self-reported sleep quality was the outcome variable. Independent variables included sociodemographic, behavioral, and health-related indicators. Poisson regression was performed to estimate prevalence ratios (PR) and their respective 95% confidence intervals (CI95%). Results: The prevalence of poor sleep quality was 15.6%. Significant associations were observed between the outcome and male gender (PR = 0.70; CI95%: 0.61 - 0.81), self-rated good health (PR = 0.49; CI95%: 0.40 - 0.60), and residence in the southern region (PR = 0.68; CI95%: 0.49 – 0.94), the number of chronic diseases (PR = 2.52; CI95%: 1.97 – 3.24, for those with two or more), and self-rated poor memory (PR = 1.30; CI95%: 1.12 – 1.51). Conclusion: Poor sleep quality in Brazilian older adults was associated with various factors, including female gender, negative perception of health and memory, excessive alcohol consumption, and the presence of multiple chronic conditions.

Keywords: Sleep Quality; Prevalence; Elderly; Aging.

INTRODUCTION
According to the World Health Organization (WHO), population aging is one of the most important health problems worldwide1. The global population, aged 65 and over, is expected to double by 20402. In Brazil, approximately 30 million Brazilians are aged 60 or over, which is equivalent to 14% of the total population in 20233. Simultaneously, and partly as a consequence of population aging, there has been a change in the profile of the most prevalent diseases, with the predominance of Noncommunicable Diseases (NCDs), whose incidence and mortality increase in direct proportion to the average age of the population4.
An important aspect associated with aging is a decline in sleep quality. It is estimated that approximately 50% of all adults aged 50 and over have problems sleeping, including initiating and maintaining sleep5. Sleep disorders are more common in older individuals because the prevalence of factors that negatively affect sleep increases with age, such as depressed mood, anxiety, stress, obesity, respiratory symptoms, perceived health from fair to poor, and physical disability6.
Sleep is closely linked to the proper functioning of the nervous, cardiovascular, metabolic, and immune systems, as well as to almost all other physiological systems in the body. There is a mutually facilitating relationship between these systems and sleep in such a way that insomnia nearly always leads to a deviation from the body\'s homeostatic functioning7.
Observational epidemiological studies suggest that poor sleep quality may be associated with an increased risk of adverse health outcomes, such as total mortality, cardiovascular disease, type 2 diabetes mellitus, obesity, and respiratory disorders8,9,10,11. Roth et al. found reports of poor health, less energy, and worse cognitive functioning among people with sleep disorders when compared to people with normal sleep8.
Sleep quality and associated factors have mainly been investigated in Europe, North America, and Asia, and studies have shown a broad variation in the prevalence of poor sleep quality. In Portugal, the estimate was 10.1% of the adult population9; in Canada there was a variation of 10% to 35%10,11; in Japan, 25.6%12; in China, 33.8%13; and in South Korea, 38%14. One study, conducted by the SAGE-INDEPTH collaboration of the WHO with more than 40,000 individuals from eight countries in Africa and Asia, showed that 16.6% of older adults in low-income settings reported severe/extreme nighttime sleep problems, with a higher prevalence among women and older age groups15.
Few studies have involved Latin American populations, and it is important to identify factors that influence sleep in different cultures. In Brazil, the frequency of sleep complaints in the general population has been assessed in previous studies conducted in the states of São Paulo, Paraná, and Santa Catarina, which reported estimates ranging from 21% to 64.9%16–19. However, these studies used a restricted sample of the population, and only one study examined the factors associated with sleep problems among adults. However, only health variables were analyzed as possible associated factors20. In this light, the present study aimed to identify the prevalence and factors associated with self-reported poor sleep quality in Brazilian adults and elderly individuals, aged 50 years or older.

METHODOLOGY
Sample
This is a cross-sectional study that used data produced by the Brazilian Longitudinal Study of Aging (ELSI-Brazil). The ELSI-Brazil sample was designed to represent the Brazilian population, aged 50 years and over. Data from the Demographic Census conducted by the Brazilian Institute of Geography and Statistics (IBGE) in 2010 were used to prepare the sample.
The sample was selected in strata, according to the size of the population living in the municipalities. For municipalities with up to 750,000 inhabitants, the selection was made in three stages (municipality, census tract, and household), and for large municipalities, in two stages (census tract and household). Residents of 70 Brazilian municipalities from all regions of the country were interviewed. The final sample of the study was 9,849, representing the Brazilian population, aged 50 years and over, who were not institutionalized. The initial assessment of the study included four stages: home interviews, individual interviews, physical measurements, and blood tests. The data used originated from the study’s baseline, conducted from 2019 to 2021. Further details on the methodological procedures of the study were published in a previous work21.
The dependent variable of the present study was self-reported sleep quality. This variable was obtained through the following question from the ELSI – Brazil individual questionnaire: “How do you rate the quality of your sleep?” This question has five different answers: very good, good, fair, poor, and very poor. These answers were dichotomized as poor sleep (poor and very poor) and good sleep (fair, good, and very good). Although dichotomizing Likert scale responses results in a loss of information, it simplifies statistical analysis and facilitates the understanding of the results22.
In addition, sociodemographic characteristics were collected: sex, age group (50-59, 60-69, 70-79, ≥80 years), skin color (white, brown, black, others – yellow and indigenous). The number of people who self-identified as yellow (n = 27) or indigenous (n = 38) was very small, even smaller than the number of individuals who responded "I don\'t know" (n = 76). For this reason, these two groups were grouped into a single race/skin color category called "others". Marital status (single, married/cohabiting/stable union, divorced or separated, widowed), geographic region, area of residence (urban/rural), years of education (<5, 5-8, ≥9). Per capita household income was categorized into tertiles (low, medium, and high).
Health conditions: Self-perceived health (bad/good), self-assessed memory (bad/good). Number of NCDs (none, one, two or more). Chronic diseases were assessed by self-reporting previous medical diagnosis and included the following conditions: diabetes mellitus, coronary heart disease (heart attack, angina, and heart failure), stroke, chronic lung disease, arthritis, asthma, depression, cancer, and kidney failure. Polypharmacy (yes/no), defined as the use of four or more medications simultaneously22. Whether the participant has a health plan (yes/no)
Nutritional status was defined using the Body Mass Index (BMI), which is calculated as the ratio between weight (in kilograms) and height squared (in meters). For adults (up to 59 years), nutritional status was classified according to the WHO criteria23 as follows: eutrophic (BMI ≥ 18.5 to 24.9 kg/m²), underweight (BMI < 18.5 kg/m²), overweight (BMI ≥ 25.0 to 29.9 kg/m²), and obesity (BMI ≥ 30 kg/m²). For the elderly (≥60 years), the classification of the Pan American Health Organization (PAHO)24 was used: eutrophic (BMI > 23.0 and < 28.0 kg/m²), underweight (BMI ≤ 23.0 kg/m²), overweight (BMI ≥ 28.0 and < 30.0 kg/m²), and obesity (BMI ≥ 30 kg/m²). Waist circumference was classified as normal or increased, according to the cutoff points for cardiovascular risk as set forth by the WHO: >94 cm for men and >80 cm for women25.

Data Analysis
Descriptive analysis was performed using weighted proportions of independent variables. Categorical variables were compared between the good and poor sleep groups using Pearson\'s chi-square test with Rao Scott correction, which is suitable for complex samples. To verify possible perfect correlations between independent variables, the variance inflation factor (VIF) test was used. The results of the VIF test were less than 5, indicating the absence of multicollinearity. Variables with p<0.20 in the bivariate analyses were selected for the multiple model, which was adjusted for all variables. Poisson regression with robust variance was used for the model. Prevalence ratios (PR) and their respective confidence intervals (CI) were estimated. Variables with p<0.05 were maintained in the final model, and a 95% Confidence Interval (95% CI) was adopted. All analyses were performed using the Stata package (College Station, Texas, USA), version 17.0, in survey mode, which allows the inclusion of the sample weight calculated for individuals.

Ethical aspects
ELSI-Brazil was approved by the Research Ethics Committee of the René Rachou Institute of the Oswaldo Cruz Foundation, Minas Gerais (CAAE 34649814.3.0000.5091). All participants signed an informed consent form before participating in the interviews and physical assessments.

RESULTS
The descriptive results obtained from a sample of 9,849 individuals showed that 15.6% of the adults over 50 years of age perceived their sleep as poor. Further information on the sample characteristics is described in Table 1.
Gender showed a significant positive association (p<0.001) with poor sleep quality, which was more prevalent among women (18.6%) than among men (11.4%). Significant differences were also observed regarding race/skin color. The prevalence of poor sleep was higher among those who self-reported themselves as black (18.3%) and lower among those who self-reported themselves as white (14.0%). Among those who assessed their health as poor, 34.8% were dissatisfied with the quality of their sleep. A directly proportional relationship was found between the number of chronic diseases and poor sleep quality. Those without chronic conditions had a prevalence of 7.1%, while those with one condition showed a prevalence of 13.0% and those with two or more conditions showed a prevalence of 24.3%. Significant differences were observed in relation to education. Among those with less than five years of education, 17.0% showed poor sleep quality. For those with 5 to 8 years of education, the prevalence was 14.2%, while for those with more than 9 years of education, the prevalence was 13.6%.
Table 2 shows the prevalence ratios and their corresponding confidence intervals, obtained through multiple analysis. After adjusting for all variables in the model, our study found a 30% decrease in the prevalence of poor sleep quality among men (PR = 0.70; 95% CI: 0.61 - 0.81) when compared to women. Regarding self-rated health, those who self-rated their health as good have, on average, a prevalence of 51% lower than those who rated it as poor (PR = 0.49; 95% CI: 0.40 - 0.60). The association with geographic region indicates that the prevalence of poor sleep is expected to be 32% lower among residents of the South region (PR = 0.68; 95% CI: 0.49 - 0.94) of the country, as compared to those living in the North region. One factor strongly associated with sleep quality is the number of chronic conditions present in the individual. The greater the number of existing morbidities, the higher the prevalence ratio (PR = 1.61; 95% CI: 1.23–2.11 for those with one condition and PR: 2.52; 95% CI: 1.97–3.24 for those with two or more). Excessive alcohol consumption was associated with a higher prevalence of poor sleep quality (PR = 2.40; 95% CI: 1.29–4.46). The expected prevalence of poor sleep among individuals who rated their memory as poor was 30% higher (PR = 1.30; 95% CI: 1.12–1.51) than among those who rated it as good.

DISCUSSION
The present study estimated the prevalence of poor sleep quality at 15.6% among Brazilians over 50 years of age, with notable disparities regarding gender. Strong associations were found between sleep quality and health status, expressed in different variables, such as the number of chronic conditions, self-rated health, and self-rated memory. It was also identified that alcohol consumption and geographic region are associated with sleep quality. Although the prevalence of sleep problems varies widely, depending on the population, this result is in line with the literature. In Brazil, the states of São Paulo, Paraná, and Santa Catarina reported estimates ranging from 21% to 64.9%16–19. In a study conducted in eight different countries, the prevalence of poor sleep quality ranged from 3.9% to over 40%26. One previous study found that 15.7% of 7,154 older adults, aged ≥60 years, in China reported moderate to severe sleep problems, as measured by a question on sleep quality27. Another study of individuals, aged 50–70 years, in Beijing and Shanghai, found that 16% of 3,289 participants reported poor sleep quality, as measured by self-reported sleep duration28. In a study of older adults, aged ≥65 years, in 22 provinces in China, 35% of the 15,638 participants reported fair to very poor sleep quality29.
Regarding gender, as in the current research, studies in general demonstrate a higher prevalence of sleep problems among women30–32. Women generally report more health problems than men, seek health services more frequently, demonstrate greater attention to the signs and symptoms of diseases, and assume the role of being sick and reporting symptoms with less embarrassment33. The differences observed in the prevalence of poor sleep quality may be due to hormonal changes related to menopausal symptoms and associated with physical, physiological, and psychological changes that may increase the incidence of sleep-related problems. In addition, it is possible that changes in sleep quality are more common among women due to the work overload they face, performing such roles as mothers, housewives, and professionals. This overload can cause rest moments to be directed towards performing tasks, which can negatively affect sleep34.
Regarding geographic region, the results show a decrease in the prevalence of sleep-related problems among residents of the South region of the country, when compared to the North region. Recent studies have shown that sleep is influenced and shaped by cultural factors, including cultural values, beliefs and practices35. One study, conducted with data from the 2010 Brazilian census, showed a regional effect on the total number of sleep-related complaints, demonstrating that in the South region, individuals presented fewer complaints when compared to the Northeast and Southeast36. Other studies conducted in different regions of Brazil – South, Southeast, and Midwest – also reported a different prevalence of poor sleep quality in adults16–18. In addition to cultural differences, environmental factors can also influence sleep quality. Higher temperatures and humidity impair sleep, leading to longer periods of wakefulness and less rapid eye movement and slow-wave sleep among those exposed to extreme heat37. This fact may help explain the association found in this study, since the North and South regions showed the highest temperatures recorded in Brazil38.
Poor sleep quality has proven to be associated with people rating their health as poor. There is a close relationship between self-rated health status and self-rated sleep problems, indicating that being satisfied with sleep quality is a major factor in self-rated health39. Observational studies have shown a significant association between sleep problems and sleep duration with self-rated poor health. The results suggest that sleep problems are important factors in determining the health of older adults in low- and middle-income countries40,41. One possible mechanism by which sleep quality may be associated with self-rated health is its potential to signal low-grade inflammation. Sleep disturbances and inflammation often occur together and are increasingly recognized as a prevalent symptom cluster42–44. Experimental research that has elicited acute inflammation by administering immune activators, such as lipopolysaccharide (LPS) and Salmonella typhi, or in patients undergoing immunotherapy, has demonstrated that this inflammation can cause fatigue, sleep disturbances, and reduced self-perceived health45–47. These findings suggest that inflammation may be a common link between sleep quality and self-perceived health. However, low-grade inflammation, which is a physiological process, is often not detectable without overt medical symptoms48. Although speculative, it is possible that fatigue and sleep quality may serve as indicators of low-grade inflammation, thereby influencing one’s perception of health.
Another factor associated with poor sleep quality found in this study is the fact that the individual has one or more chronic diseases. Previous studies have shown that poor sleep is associated with several diseases, such as lung disease, gastrointestinal problems, chronic kidney disease, fibromyalgia, infectious diseases, menopause, and cancer49,50. The associations between sleep problems and chronic conditions can be explained by the coexistence of sleep-disordered breathing in such conditions as chronic lung disease, diabetes, and stroke, or by the symptoms of the chronic conditions themselves (e.g., nocturnal symptoms in asthma, COPD, and nocturia in diabetes)51. The association between arthritis and sleep problems can be mediated by pain and physical limitations52. Mental illnesses are the conditions most likely to coexist with chronic insomnia, and sleep problems are one of the main symptoms of depression and anxiety, which have also been related to the subsequent development of many psychiatric disorders53. Finally, these associations can also be explained by the psychological distress and anxiety associated with these conditions. The results obtained in the study allow us to establish an association between sleep disorders and a self-assessment of memory quality. This result is consistent with the evidence in the current literature54,55. One systematic review demonstrated that individuals with sleep disorders have a higher risk of memory loss when compared to those without sleep problems55. Another study also confirmed this result, indicating that 70% of all patients with initial memory loss have sleep disorders, and that these disorders are predictors of more severe cognitive and neurological symptoms, in addition to a worse quality of life54. It is important to emphasize that both sleep disorders and memory loss are multifactorial conditions, and the results obtained corroborate the positive association between these two conditions.
One of the possible limitations of this study is that sleep quality was self-reported rather than using a validated assessment instrument. However, studies have shown that self-reporting is equally effective in assessing sleep quality when compared to a validated questionnaire used for this purpose56,57. In addition, it is important to consider that the information provided by the participants was self-reported and refers to past behaviors and events, which may introduce memory bias and differences in interpretation by the interviewees. Another factor to be considered is that the data were obtained through the application of a questionnaire in different Brazilian locations, which may have population and even cultural diversity, which can affect the understanding of the questions. This study demonstrates significant characteristics, as it is a comprehensive nationwide survey on sleep problems. The study included more than 9,000 participants over 50 years of age, covering sociodemographic factors, lifestyle behaviors, and health conditions. Finally, it can be concluded that the prevalence of sleep problems in the population of adults over 50 years of age in Brazil is similar to that found in the same population in other underdeveloped countries. This multivariate analysis identified associations between the variable of sleep problems and sociodemographic factors, health conditions, and lifestyle. Thus, the results of this study contribute to current evidence on the relationship between sleep and health determinants, highlighting the need for more specific longitudinal studies to better understand and characterize sleep problems in the population of older adults in Brazil.

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