Individual-and state-level factors associated with functional limitation prevalence among Colombian elderly : a multilevel analysis

This study aimed to identify the main regional factors associated with variations in the prevalence of functional limitation on the older adult in Colombia adjusted by individual characteristics. This multilevel study used cross-sectional data from 23,694 adults over 60 years of age in the SABE, Colombia nationwide survey. State-level factors (poverty, development, inequity, violence, health coverage, and access to improved water sources), as well as individual health related, socioeconomic and demographic characteristics, were analyzed. The overall prevalence of functional impairment for the basic activities of daily living (ADL) was 22%. The presence of comorbidities, low educational level, physical inactivity, no participation in social groups, mistreatment and being over 75 years old were associated with functional limitation. At the group level, the analysis showed significant differences in the functional limitation prevalence across states, particularly regarding the socioeconomic status measured according to the Human Development Index (median OR = 1.22; 95%CI: 1.13-1.30; p = 0.011). This study provides evidence on the impact of socioeconomic variation across states on FL prevalence in the Colombian elderly once adjusted for individual characteristics. The findings of this study, through a multilevel approach methodology, provide information to effectively address the conditions that affect the functionality in this population through the identification and prioritization of public health care in groups with economic and health vulnerability. Activities of Daily Living; Aged; Socioeconomic Factors; Multilevel Analysis Correspondence S. M. Ballesteros Universidad del Rosario, Cundinamarca, Colombia. Carrera 105 F # 70 C 23, Bogotá, Cundinamarca, 111221, Colombia. silvia.ballesteros@urosario.edu.co 1 Universidad del Rosario, Bogotá, Colombia. 2 Universidad El Bosque, Bogotá, Colombia. doi: 10.1590/0102-311X00163717 Cad. Saúde Pública 2018; 34(8):e00163717 ARTIGO ARTICLE This article is published in Open Access under the Creative Commons Attribution license, which allows use, distribution, and reproduction in any medium, without restrictions, as long as the original work is correctly cited. Ballesteros SM, Moreno-Montoya J 2 Cad. Saúde Pública 2018; 34(8):e00163717 Introduction Functional limitation, defined as decreased ability of an individual to independently perform activities of daily living (ADL) 1, is strongly associated with increased prevalence of falls, depression and decreased quality of life in the elderly population 2,3,4. Functional decline also impacts on economic and social factors as it is related to augmented mortality rates and health care costs 5,6. In developed countries, the functional limitation prevalence varies from 9.6 to 12.3% 2,5, while in developing countries it affects between 13 to 28% of the older adults 7,8, being the latter the most affected, due to the demographic transition 9,10, with growth rates of older adults almost three times higher than in developed regions 11. Demographic reports indicate that the functional limitation prevalence is larger with aging 12,13,14 and sex (females) 8,15,16, and associated with poor self-perceived health 17, non-white population 13, physical inactivity 14,18, obesity 19 and presence of co-morbidities such as type 2 diabetes, stroke, depression, heart disease, hypertension and cognitive impairment 18. Moreover, individual socioeconomic status characteristics such as income 20, educational level 8,14,15, health care access 13 and occupation 8,15 have impact on elderly functionality. Besides these factors, the health status of older adults is also influenced by environmental characteristics that may act on individual and population health through different pathways such as economic opportunities and healthcare services 21. Contextual factors such as area-level wealth have been related to differences between regions in limitations for ADL. Populations living in economically developed provinces and in wealthier villages are less likely to report difficulties with ADLs 22,23. In this regard, the resource availability of a region to fulfil its population needs is reported to be associated with their mental and physical health 21,24. Previous studies indicate that regional socioeconomic deprivation and inequality have a negative impact on the facilities for physical activity and on the availability and accessibility to healthy food 25,26; therefore, these factors are related to increased prevalence of chronic conditions such as diabetes and hypertension in older adults 21,27; conditions whose association with poor performance in ADL has been previously reported 14,18. Prior research also indicates that elderly individuals living in wealthier villages experience fewer depressive symptoms 24. Furthermore, depression is associated with decreases in energy production to perform activities and consequently with alterations in functional capacity 14. However, in particular contexts, as China, it has been found higher per capita gross domestic product (GDP) at the community level is associated with a higher rate of ADL disability of older people 28. In addition, the region’s income inequality has also been related to ADL prevalence discrepancies between areas. Previous reports indicate that the odds of having ADL limitations for an individual in a state with the highest inequality is approximately 32% higher than those in the states with the lowest income inequality 29. Neighborhood safety has also been related to ADL in elderly population. Longitudinal studies claim that older adults who reported to be functionally independent at baseline and considered their neighborhood to be unsafe were 21% more likely to experience functional decline after 10-year follow-up compared with those who perceived their neighborhood to be very safe 30. On the other hand, inequalities in the availability of health care services at the regional level have been associated with health disparities between provinces in China 31. Moreover, previous research indicates that older adults living in states with higher percentages of uninsured population and lowerthan-average annual per capita health expenditure had lower odds of receiving quality preventative care 32. Furthermore, adequate access to health services is suggested to delay functional decline among aged population 13. Other contextual factors such as having a sewage system and a continuous supply of electricity were associated with reduced physical limitations 22. Area-level resources have reported to be more influent in the maintenance of health for the elderly population than for their younger counterparts 33. Nonetheless, comprehensive research for factors related to elderly ADL disability is still sparse in the Colombian population. Therefore, this study aimed to identify the regional factors related to the functional limitation prevalence across states in Colombian elderly after individual characteristics’ adjustment. CONTEXT FACTORS ASSOCIATED WITH FUNCTIONAL LIMITATION IN THE ELDERLY 3 Cad. Saúde Pública 2018; 34(8):e00163717 Methods


Introduction
Functional limitation, defined as decreased ability of an individual to independently perform activities of daily living (ADL) 1 , is strongly associated with increased prevalence of falls, depression and decreased quality of life in the elderly population 2,3,4 .Functional decline also impacts on economic and social factors as it is related to augmented mortality rates and health care costs 5,6 .In developed countries, the functional limitation prevalence varies from 9.6 to 12.3% 2,5 , while in developing countries it affects between 13 to 28% of the older adults 7,8 , being the latter the most affected, due to the demographic transition 9,10 , with growth rates of older adults almost three times higher than in developed regions 11 .
Demographic reports indicate that the functional limitation prevalence is larger with aging 12,13,14 and sex (females) 8,15,16 , and associated with poor self-perceived health 17 , non-white population 13 , physical inactivity 14,18 , obesity 19 and presence of co-morbidities such as type 2 diabetes, stroke, depression, heart disease, hypertension and cognitive impairment 18 .Moreover, individual socioeconomic status characteristics such as income 20 , educational level 8,14,15 , health care access 13 and occupation 8,15 have impact on elderly functionality.
Besides these factors, the health status of older adults is also influenced by environmental characteristics that may act on individual and population health through different pathways such as economic opportunities and healthcare services 21 .Contextual factors such as area-level wealth have been related to differences between regions in limitations for ADL.Populations living in economically developed provinces and in wealthier villages are less likely to report difficulties with ADLs 22,23 .In this regard, the resource availability of a region to fulfil its population needs is reported to be associated with their mental and physical health 21,24 .Previous studies indicate that regional socioeconomic deprivation and inequality have a negative impact on the facilities for physical activity and on the availability and accessibility to healthy food 25,26 ; therefore, these factors are related to increased prevalence of chronic conditions such as diabetes and hypertension in older adults 21,27 ; conditions whose association with poor performance in ADL has been previously reported 14,18 .Prior research also indicates that elderly individuals living in wealthier villages experience fewer depressive symptoms 24 .Furthermore, depression is associated with decreases in energy production to perform activities and consequently with alterations in functional capacity 14 .However, in particular contexts, as China, it has been found higher per capita gross domestic product (GDP) at the community level is associated with a higher rate of ADL disability of older people 28 .
In addition, the region's income inequality has also been related to ADL prevalence discrepancies between areas.Previous reports indicate that the odds of having ADL limitations for an individual in a state with the highest inequality is approximately 32% higher than those in the states with the lowest income inequality 29 .Neighborhood safety has also been related to ADL in elderly population.Longitudinal studies claim that older adults who reported to be functionally independent at baseline and considered their neighborhood to be unsafe were 21% more likely to experience functional decline after 10-year follow-up compared with those who perceived their neighborhood to be very safe 30 .
On the other hand, inequalities in the availability of health care services at the regional level have been associated with health disparities between provinces in China 31 .Moreover, previous research indicates that older adults living in states with higher percentages of uninsured population and lowerthan-average annual per capita health expenditure had lower odds of receiving quality preventative care 32 .Furthermore, adequate access to health services is suggested to delay functional decline among aged population 13 .Other contextual factors such as having a sewage system and a continuous supply of electricity were associated with reduced physical limitations 22 .
Area-level resources have reported to be more influent in the maintenance of health for the elderly population than for their younger counterparts 33 .Nonetheless, comprehensive research for factors related to elderly ADL disability is still sparse in the Colombian population.Therefore, this study aimed to identify the regional factors related to the functional limitation prevalence across states in Colombian elderly after individual characteristics' adjustment.

Individual-level variables
Functional status was measured using the Barthel Index scale, which covers the self-report independence in performing ten basic ADLs including, bathing, dressing, grooming, toileting, feeding, continence, transferring, mobility and use of stairs 35 .Functional limitation was defined herein by the report of difficulty in performing at least one of these activities 8 .Independent individual variables such as sex, age, educational level, self-reported comorbidities, lifestyle characteristics, mistreatment, income, participation in social groups, presence of barriers to health services and internal displacement due to armed conflict were included in the analyses.

Regional-level variables
Regional socioeconomic status were analyzed using the following state-level variables: the Unsatisfied Basic Needs index (UBN) in 2011 36 , the Gini coefficient in 2014 37 , the Human Development Index (HDI) in 2010 38 , the participation percentage in the national GDP of 2014 39 and percentage of the population without access to improved water sources in 2005 40 .States healthcare services were assessed by the percentage of health coverage in 2014 (Ministerio de Salud y Protección Social de Colombia.Estadísticas -afiliados cargados BDUA marzo 2014.https://www.minsalud.gov.co/estadisticas/Estadsticas/Forms/DispForm.aspx?ID=1046, accessed on 20/Apr/2017); and violence was analyzed using the homicide rate per 100,000 inhabitants in 2014 41 .

Statistical analysis
Study sample characteristics were assessed by using absolute and relative frequencies with 95% confidence intervals (95%CI) for qualitative variables, as well as measures of central tendency and dispersion were calculated for quantitative variables.Differences in baseline characteristics were compared using independent χ 2 test; variables with p-values below 20% were included in the adjusted models.A preliminary evaluation of the effect of individual-level variables was performed by 1-level stepwise logistic model, significant variables (p < 0.05) were included in the multilevel model.A first empty model (intercept only) was used to assess geographic variation, and the suitability of the 2-level approach was evaluated with the intraclass correlation coefficient.The associations and variance between individual variables and functional limitations were evaluated using odds ratios (ORs) and 95%CI in the fixed-effects part of the models.For the selection of the variables at state level, Wald tests were developed to evaluate their significance regarding the functional limitation prevalence.For the adjustment of regional-level variables, a two-level logit model 42 was used taking as random effects the state variables.To evaluate the variability in prevalence between regions, a median OR (MOR) Cad. Saúde Pública 2018; 34(8):e00163717 was used to generate a reference value for comparison between two potential subjects in regions with opposite values of the regional aggregation variable under study.The MOR translates the area-level variance, due to area-level variables, to the odds ratio scale; therefore, MOR is a measure that allows comparison with the individual OR.In this research, this value shows the extent to which the individual probability of functional limitation is determined by the state-level variables 43 .All analyses were carried out using Stata version 14 software (StataCorp LP, Colege Station, USA).

Results
The overall functional impairment prevalence for ADL was 22% (95%CI: reported suffering from some type of mistreatment by the members of their household during the three months before the application of the survey and 28.5% (95%CI: 28.14-28.86)reported having at least one access barrier to healthcare services, such as delay of appointment allocation and refusal to provide medications or medical procedures.About individual SES characteristics, most of the older adults (68.7%; 95%CI: 67.75-69.65)have an income of less than 7.83 dollars per day and 93.4% (95%CI: 92.21-94.59)have secondary education or lower (Table 1).
All crude comparisons among individual characteristics showed significant differences between subjects with and without functional limitation, except for smoking and urban/rural residence (Table 1).The prevalence of chronic diseases, overweight, mistreatment and physical inactivity were significantly higher among subjects withfunctional limitation, as well as the proportion of people with low education level (Table 1).The HDI (MOR = 1.186; 95%CI: 1.124-1.249;p = 0.009) and the percentage of participation in the national GDP (MOR = 1.017; 95%CI: 1.016-1.017;p < 0.001) were the only state-level variables that achieved statistical convergence and had a significant effect in the crude analysis without individual-level variable adjustments.
The adjusted analysis (Model II, Table 2) showed that secondary education level or lower, poor self-perceived health, no participation in social groups, age 75 or older, low subjective quality of vision, experience of falls during the last year, physical inactivity, mistreatment, and comorbidities such as depression, cognitive impairment, hypertension, diabetes and respiratory, cerebrovascular and mental diseases were factors associated with functional limitation.
The estimation of regional variance, by a null model analysis, showed inter-state variability regarding functional limitation prevalence was statistically significant (p < 0.001; intraclass correlation coefficient = 2.9%).In the multilevel models adjusted for individual-level variables, except for percentage of population without access to improved water sources, in which the convergence of the statistical model was not achieved, all state-level variables had significant effects regarding functional limitations prevalence (Table 3).
Nonetheless, the models with multiple state-level variables did not achieve statistical convergence, hence correlations between state-level variables were assessed.Strong correlations were identified between HDI and UBN, GDP, and percentage of the population without access to improved water sources.Medium strength correlations were identified between Gini and water access, percentage of population with health coverage and UBN, and GDP with homicide rate (Table 4).Due to these correlations and considering that the HDI is a measure that represents several dimensions of a region socioeconomic status, HDI was the state-level variable used to explain the plausible association between environmental socioeconomic characteristics and individual functional limitations (Model III, Table 2).The inclusion of regional variables had minimal effects on the ORs estimated for individual-level variables (Table 2).

Discussion
This study verified that the functional limitations prevalence for ADLs in Colombian elderly varies regarding individual characteristics and factors that affect the subjects collectively, in particular the regional socioeconomic level; this situation reflects lags on the access, use or quality of primary prevention and health care services 44,45,46 .Similar findings have previously been reported for other chronic diseases, including mental illness 47 , type 2 diabetes 21 , hypertension 27 and coronary disease 45 .
As reported previously, low human development has been associated with lesser functional levels, in particular poor self-care prevalence has reported to be higher in low income countries 48 , and individuals living in highly developed regions reported better physical health than those living in developing regions 49 .Deprived regions are linked to high area-level crime rates, which has been correlated to physical inactivity and social isolation and, thus, functional decline 30 .Disadvantaged area-level socioeconomic status has also been related to reduced cohesiveness 50    participate in their community in actions that promote health, thereby it is related to fewer ADL disabilities 51 .The human development index is also an indicator of the population literacy.Former literature report higher prevalence of self-care limitations in the lowest education level population compared with the highest 48 .For this work, HDI was considered as a proximal or indicator variable of the effect derived from any or several development or deprivation aspects in communities regarding functional limitations.Low human development, as an indicator of low regional socioeconomic status 46 , has also previously been related to increased prevalence of health conditions that affect functional independence 27 .It is reported that disadvantaged regions show higher food insecurity prevalence 21,25 and lower access to sport areas 26 , factors associated with chronic conditions like diabetes 21 , whose consequent complications such as neuropathies, loss of limbs, cognitive impairment and microvascular dysfunction may affect motion capacity 52 .Also, psychosocial stress and depression, caused by higher rates of violence and low levels of social support, may be factors linked with the mechanism that links individual functional capacity to perform tasks with regional economic deprivation 21,50,53 .
As in previous research, this study verified the association between functional limitations and individual variables such as age 12,13,14 , educational level 12,14 , participation in social groups 12,18,54 , physical activity 14,18,55 , and the presence of comorbidities 12,13,14,18 .However, the effect of overweight was discarded.In this regard, previous findings state the deficiency of body mass index (BMI) as an indicator of the probability of developing chronic diseases given its limitations to characterize body composition 56,57 .On the other hand, the relationship between low body weight and decreased muscle strength with individuals' mobility affectations has been consistently reported 12,14 .
Cad. Saúde Pública 2018; 34(8):e00163717 The self-reported perception of access barriers to healthcare did not have a significant association with function limitations in this study.Previous research has reported that elderly subjects without private supplemental health insurance (medication and diagnostic test coverage) are more likely to suffer chronic diseases related to function limitations than their counterpart with such coverage; however, among individuals with functional impairment, private supplemental insurance is not correlated to improving or weakening functional status 13 .
Mistreatment was also associated with functional limitations in the current study.Previous research indicates that the presence of multiple types of abuse in the elderly population is associated with the manifestation of depressive symptoms and cognitive deficit 58,59 , health conditions whose negative impact on the physical and intellectual capacity of subjects to preserve independence has been widely reported 12,14,17,18 .
Our findings, however, have some limitations.Due to the cross-sectional nature of the data, derived inferences must be analyzed in the scenario of temporal transversality, in which it is impossible to define the temporality of causal inferences, and which could be bidirectional.Another limitation resides in the use of self-reports 60 , implying the use of perceptions, a situation that can distort the evaluation of the effect of the exposures of interest in a non-differential way; and in the lack of simultaneity of secondary sources, which does not guarantee the contemporaneity of the described effects 61 .Moreover, further studies may include area-level factors such as social cohesion and social capital, which have been previously reported to play a role in the functional disability onset 51 .
Nonetheless, this study provides evidence on the impact of regional socioeconomic variation on the functiona limitations prevalence for ADL in Colombian elderly.As the context is similar to other scenarios in the region, this study may constitute a benchmark to strengthen the understanding of the phenomena inherent to the aging process in the Latin American population.Also, this study provides information for the identification and priorization of public health care in groups with economic and health vulnerability 21,46,62 .Consistent with other studies, the evidence provided here reiterates the importance of caring for the elderly and the control of chronic diseases, particularly in a growing demographic transition framework 10 .Therefore, the use of regional and individual information allows to effectively address the information research for the control and prevention of conditions that affect the functional status of older people 63 .

Contributors
S. M. Ballesteros and J. Moreno-Montoya participated in the study conception and design, analysis and interpretation of data, drafting the paper and revising it critically for important intellectual content and final approval of the version to be published.

Table 1
Functional limitation and individual characteristics.

Table 2
Significant effects at the individual-and state-level variables.

Table 3
State-level effects in functional limitations prevalence.

Table 4
Correlations between state-level variables.
GDP: Gross Domestic Product; HDI: Human Development Index; UBN: Unsatisfied Basic Needs index.* Percentage of the population without access to improved water sources.