Prevalence of functional incapacity by gender in elderly people in Brazil : a systematic review with meta-analysis

1 Universidade Federal do Sul e Sudeste do Pará, Instituto de Estudos em Saúde e Biológicas. Marabá, Pará, Brasil. 2 Universidade de São Paulo, Faculdade de Medicina, Departamento de Fisioterapia, Fonoaudiologia e Terapia Ocupacional. São Paulo, São Paulo, Brasil. 3 Associação de Pais e Amigos dos Excepcionais, Setor de Terapia Ocupacional. Lavras, Minas Gerais, Brasil. 4 Pontifícia Universidade Católica de Minas Gerais, Instituto de Ciências Exatas e Informática, Departamento de Matemática. Belo Horizonte, Minas Gerais, Brasil.


INTRODUCTION
Maintaining functional capacity is considered to be the main parameter for the assessment of health and quality of life during the aging process. 1 From this perspective, the promotion of healthy aging can involve the adoption and consolidation of active lifestyles that include frequent physical activity, the diversification of one's daily routine, and active participation in groups as possible ways of exercising functional capacity. 2 As a result, measures to promote health and the prevention of disease, along with the appropriate management of existing comorbidities, are aimed at maintaining this capacity and preventing disabilities.
According to the World Health Organization (WHO), 3 functional incapacity can be understood as the process of losing the ability to perform the daily tasks necessary for an independent and autonomous life.From a practical standpoint, this ability can be measured by the performance of daily activities, which are didactically divided into basic activities of daily living (BADL) such as bathing, eating, using the toilet and walking through the rooms of the house, and instrumental activities of daily living (IADL), such as shopping, performing housework and preparing meals.It has been shown that there is a dose-response type association between age and the prevalence of functional incapacity, and that aging is different for men and women. 5,6However, most such studies involve representative samples of municipal districts or states, and not nationwide research.
Considering the importance of functional capacity as a health indicator for the elderly and the scattered information on the topic in Brazilian research, the present study aimed to describe the prevalence of functional incapacity by gender among elderly Brazilian individuals through a systematic review and meta-analysis of articles on the topic.

METHOD
In this systematic review and meta-analysis, we sought to answer the following question: Are there differences by gender in the prevalence of functional incapacity among elderly Brazilians?
A search for articles published up to June 2013 was performed in the MEDLINE, SciELO, LILACS, Scopus, Web of Science and Science Direct electronic databases.
The descriptors used in the review process were selected after consulting the Bireme DeCS Health Sciences Descriptors.The search was conducted in English using concepts grouped into three blocks.The first included terms related to functional capacity ("functional assessment", "functionality", "daily activities") the second with terms related to aging ("old" and "old age") and the third with terms related to Brazil ("Brazil").To combine these descriptors, we used the logical operator "OR" within each block and the logical operator "AND" to combine the blocks.The same search strategy was used in all the databases surveyed.
We chose not to employ any restrictions related to the size of the data, language, type of study or sample or publication period.Although the studies did not cover the same time periods, we did not exclude articles based on publication period to ensure that all the studies of potential relevance to the review were included.
The inclusion criteria were: a population sample consisting only of elderly persons (aged 60 years or over); assessment of functional capacity to calculate the prevalence of incapacity by gender, and data collection carried out in Brazil.Articles were excluded if they were limited to specific health conditions among the elderly (obesity, hypertension, diabetes, dementia and other diseases).In addition, the authors chose to exclude theses, dissertations and monographs, as systematic research on this topic for these works would not be viable.
Articles were firstly selected by title and abstract and then through a full reading.Each article was reviewed and selected by two reviewers.Where there was disagreement, a third person was consulted.Duplicate articles, with identical results published in different magazines, were checked to allow the exclusion of one of the studies.In the case of the duplication of articles from more than one database, the version with the widest scope was maintained.
In addition to prevalence of functional incapacity, the articles selected were mapped in relation to type of study, location, sample size, age of participants, type of statistical analysis and the method of evaluation and classification of functional capacity.
In the case of items with incomplete information, three attempts were made to contact the corresponding author via e-mail, between the months of August and September 2013, in order to seek additional information.A standard e-mail was sent to the authors, requesting the following information: n total of statistical analysis, percentage of men in the sample and prevalence of functional incapacity by gender.
The instruments used to assess the methodological quality of the observational articles to be included in the systematic review were Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).STROBE contains 22 items that deal with recommendations on what should be contained in a precise and complete description in an observational study. 7PRISMA is a list of specific checks for systematic review studies.It contains 27 topics and is designed to increase the quality of systematic reviews and meta-analyzes of randomized controlled trials and nonrandomized studies. 8alysis of the selected articles was carried out descriptively and in two stages.The first included: year; authorship; location; type of study; target population; study design and statistical analysis of data.The second stage comprised an analysis of the prevalence of functional incapacity by gender data with the Mantel-Haenszel test and presentation via a forest-plot graph using the BioEstat 3.0 program.

RESULTS
Figure 1 shows the flowchart of the article selection process.Of the 3,656 articles initially identified from all the databases, 2,585 duplicates were excluded and 114 articles were eligible for a full reading.It was not possible to identify the prevalence of functional incapacity in percentage form in 42 of the articles, and 28 articles did not separately assess functionality by gender.Although 44 articles were reviewed and approved according to the PRISMA and STROBE criteria, 21 articles were excluded due to a lack of response from the authors for complementary information.After this stage, 23 items were considered eligible for the systematic review.All articles present in the review defined a minimum age for inclusion in the study.A total of 19 (82.0%) studies included individuals aged 60 years of age or older; two (8.7%) included persons aged 65 or more, and the same number included individuals aged 80 or older.
Functional incapacity was measured indirectly, or in other words, based on information provided by individuals.In all the studies included in this review the BADL and IADL measurement scales were the most commonly used instruments.Five (21.7%) studies 16,19,22,30,31 used the Brazilian Multidimensional Function Assessment Questionnaire (BOMFAQ), three (13.0%)studies 10,13,14 used the Katz scale combined with the Lawton-Brody Index (LBI) and three (13.0%)studies 17,18,31 used the ABVD scale from Older American Resources and Services (OARS).Although most studies used previously validated questionnaires that provided scores, four (17.3%) 11,21,23,26 inquired about the functional capacity of older people through open questions regarding the presence of difficulty in performing one or more BADL or IADL (table 1).
With respect to the sampling process, there was significant gender variation in the composition of the samples, with only one study 27 mainly comprising men.5][16][17]19,[20][21][22][23]25 used a probabilistic sampling process based on selecting the number of participants through a draw and/ or the number of households sampled.Seven (30.4%) studies 10,12,16,21,24,28,31 did not describe the loss percentage of the sample (Table 1).
Data relating to the prevalence of functional incapacity in each study and prevalence stratified by gender is shown in Table 2.There was considerable variability in the overall prevalence results, which ranged from 13.2% to 85.0%.Prevalence rates by gender ranged from 12.3% to 94.1% for men and from 14.9% to 84.6% for women.The sample sizes of the studies also varied, with the smallest consisting of 39 elderly persons and the largest of 28,943 elderly individuals (Table 2).
Taking into account the samples of all the studies, 44,714 elderly persons were interviewed.The result of the Chi-squared and Mantel-Haenszel tests are shown in Figure 2.There was a significant statistical difference between men and women in relation to the prevalence of functional incapacity.
The proportion of functional incapacity among women was 1.51 times greater than among men ( p<0.001), with a confidence interval of between 1.43 and 1.59.This effect was not significant in only five studies (21.7%) 16,24,[26][27][28] , where the horizontal line of the Forest-plot graph crossed the vertical line.

DISCUSSION
The vast majority of studies included in this systematic review were conducted in the south and southeast of Brazil.A possible explanation for this finding would be the significant regional differences in the rate of aging, which has an effect on the scientific production of each area.A study based on 2010 census data found that population aging in Brazil is increasing rapidly, with an increase of 268.0% in the aging rate between 1970 and 2010.In terms of regional variation, in 2010 the highest rates were found in the south (54.9%) and southeast (54.5%) and the lowest rate was found in the north (21.8%). 32e samples of the selected studies were mainly composed of women, corroborating official Brazilian data.The aforementioned census results found that the gender ratio, which had been 99.8 men for every 100 women in 1960, was 96 men for every 100 women in 2010. 33is study confirmed the high prevalence of functional incapacity among elderly Brazilians and the wide variability between genders.The average prevalence was 42.8% (±21.0)among women and 39.6% (±26.2) among men.These results are similar to other Brazilian studies. 34,35 eight of the studies selected for review, 11,12,15,19,21,22,24,31 the prevalence of functional incapacity among women was higher than 50.0%.Differences in the prevalence of functional incapacity between genders were also identified in other articles. 23,36w studies have been published in Brazil that attempt to assess possible explanations for gender differences in functional incapacity, or the more accentuated loss of functional capacity among women. 14me hypotheses to explain this gender difference include the fact that women tend to report greater functional difficulties than men; 2 there are higher initial levels of incapacity among older women; 36 and greater longevity among women, which combined with limitations, may lead to dependency on care. 2 An additional hypothesis for explaining these differences is based on higher levels of widowhood among women in comparison to men. 34,35The resulting weakening of an individual's support network associated with greater life expectancy and a higher prevalence of chronic diseases increase the vulnerability of women to incapacitating conditions.
In the case of the present study, variations in prevalence can also be explained by the lack of standardization in the measures of functional capacity used and the differences in sample size between the studies.Two of the selected studies 19,24 involved octogenarians.The variability of the cutoff points used to analyze the data made it impossible to establish a relationship between age and functional capacity by gender during meta-analysis.][38] The initial results of the Rede de Estudos sobre a Fragilidade em Idosos Brasileiros (Frailty among Elderly Brazilians Study Network) (FIBRA) found a statistically significant reduction in the performance of BADL and IADL over a six-month period in a sample of 167 elderly persons in Belo Horizonte in the state of Minas Gerais. 39though important indicators have been established to define the functional incapacity of older elderly persons that hinders the performance of daily activities, Brazilian scientific production related to the functionality of this population is recent. 40e instruments used to assess functional incapacity among elderly Brazilians in literature and in this systematic review are mostly indirect and self-reported methods of evaluation, and refer to how the elderly individuals perform their daily activities, most specifically ADLs and IADLs.The advantage of using self-reported or subjective measures is that it provides information on the severity and type of limitations experienced in different situations and contexts. 41Furthermore, these questionnaires are easy to access and apply and can be good indicators for assessing incapacity and/or limitations in the physical functioning and mental health of the elderly caused by disease and other conditions associated with aging. 42The disadvantages of using these instruments include the fact that information collected through selfreporting may be influenced by the physiological, cognitive and emotional changes that occur during aging.Furthermore, for elderly individuals living in the community, some of these instruments do not have the necessary discriminatory power for all ADLs and IADLs, as the majority of such individuals are considered functionally independent.
The scales adopted in the selected studies include the BOMFAQ, 43 the Katz scale 44 and the Lawton-Brody index. 45e BOMFAQ is used to evaluate the difficulty involved in performing 15 daily activities, of which eight are classified as BADLs and seven are considered IADLs.The reported presence of difficulty or dependence involved in each of these activities is recorded, regardless of the degree of such difficulty or dependence. 43e Katz scale evaluates independence in six ADLs on three levels, through which the elderly person is classified into one of eight possible categories. 44In Brazil, the cross-cultural adaptation and validation of the Katz scale into Portuguese was performed by Lino et al. 46 The Lawton-Brody scale, assessed for reliability by Santos & Virtuoso 47 and validated by Araújo et al., 48 was also adopted in some of the studies, and evaluates independence in six BADLs, described by the authors as the physical activities of daily living, eight IADL for women and five for men, in three to five levels.There are two score possibilities, one of which considers the score for each activity and one that considers the total score.The limitations of this systematic review are related to the variability in the research types and the contexts in which data collection was performed, as well as the small number of characteristics analyzed.This may explain, at least in part, the heterogeneity of the prevalence of functional incapacity observed in the articles selected.
Considering that Brazilian scientific literature is relatively recent in relation to the calculation of prevalence of incapacity among the elderly, it was decided not to adopt a strict delimitation in the search strategy.The main selection criteria for this review were age and the absence of specific health conditions among the elderly individuals, which did not allow a full comparison between the populations.
Moreover, although all the selected studies used questionnaires and scales to measure functional capacity, the cutoff point for failure differed among the studies.These variations demonstrate the need to use standardized methods in the cross-cultural adaptation process to objectively calculate the functionality of the elderly, and investigate risk and protective factors between the genders.Despite its limitations, this review can serve as a basis for studying the influence of the clinical situation of elderly persons, and of possible associations between diseases and morbidities that can compromise the functional capacity of the elderly and therefore directly influence the prevalence of functional incapacity.

CONCLUSION
The main contribution of the present study lies in the fact that it is the first to use a systematic review and meta-analysis to investigate the prevalence of functional incapacity among the elderly by gender.It can be concluded that the prevalence of functional incapacity in elderly Brazilians is high, especially among women.The results of this systematic review also suggest that the differences between the genders need to be better investigated.The conditions necessary to enable the results of studies to be compared include the standardization of the instruments used for measuring functional disabilities, and the definition of variables and other comparable measures for the realization of meta-regression and the testing of associations between disability and possible risk factors.
It is suggested that further studies should include, as well as a rigorous design, a sample of sufficient size to allow statistical comparison between men and women, and the application of standardized instruments for monitoring longterm results.Despite the challenges observed, it is believed that the present study represents an initial effort to systematize information about functional capacity, a major health indicator for elderly persons.Further studies of this nature will allow the identification of specific groups for intervention and health promotion strategies, aimed primarily at maintaining and improving the functional capacity and autonomy of the elderly as long as possible.

Figure 2 .
Figure 2. Forest-plot of prevalence of functional incapacity of elderly Brazilian individuals by gender.Belo Horizonte, Minas Gerais, 2014.

Table 1 .
Characteristics of articles included in the review.Belo Horizonte, Minas Gerais, 2014.

Table 1
basic activities of daily living; IADL= instrumental activities of daily living; BOMFAQ= Brazilian OARS Multidimensional Function Assessment Questionnaire; LTCF= Long-term Care Facility for the Elderly; MPPT= Modified Physical Performance Test; OARS= Older American Resources and Services; LBI= Lawton-Brody Index. BADL=