brazil is among the 25 countries in the world with the fastest aging rates [ 1 , 2 ] . in 1950 , 2.6 million ( 4.9% ) brazilians were older than 60  years of age , and this number has increased to 20.6 million people ( 10.8% ) according to the 2010 census .
improvements in medical care and living standards have been shown to translate into higher life expectancy . in 1950 , for example , life expectancy at birth in brazil was 50.9  years , but the figure increased to 72.2  years in 2010 .
however , the number of disabled people is expected to increase in the coming years , given the rapid growth rate of the elderly population and the rise in the prevalence of obesity and chronic diseases .
fast changes in the population 's nutritional intake that have occurred in brazil in recent decades   have resulted in an increase in the prevalence of obesity [ 6 , 7 ] . in the past three decades , obesity rates in brazil tripled among men and almost doubled among women . with the exception of higher - income urban women ,
few studies focus on the impact of bmi on mortality and disability in the latin american and the caribbean ( lac ) region .
based on the baseline for the health , well - being , and aging in latin america and the caribbean study ( sabe ) , al snih and colleagues   showed that obese individuals were 1.6 times more likely to face difficulties performing activities of daily living ( adl ) than those with normal bmi .
corona and colleagues   found that older adults who were underweight ( bmi    23  kg / m ) and obese ( bmi    30  kg / m ) were more likely to develop limitations on instrumental activity of daily living ( iadl ) , but their analysis did not explore bmi associations with mortality or recovery from disability .
monteverde and colleagues   found that , based on relative cutoffs ( quintiles ) , heavier older adults in mexico face higher mortality risks than those in the united states .
however , when bmi was categorized following the traditional world health organization cutoffs , no excess mortality was found among overweight and obese subjects . in fact , coefficients for overweight and obesity were not in the expected direction . however , none of these studies jointly examined the association between bmi , disability transitions , and mortality .
we examine the association between body mass index and weight changes on disability transitions and mortality .  
obesity has been associated with higher prevalence of disability in cross - sectional and longitudinal studies [ 4 , 1113 ] .
this positive association has been found among middle- and older - aged adults [ 1315 ] , and it appears that this association has not changed over time [ 16 , 17 ] .
additionally , the association between body mass index ( bmi ) and disability is strongest among those who are underweight ( bmi  <  18.5  kg / m ) and among obese subjects ( bmi  >  30 
obese women face higher prevalence of mobility impairment than men . in the united states , severe functional limitations are higher among older adults who gain or lose weight after age 50 compared to those with stable weight .
emerging evidence supports the proposition that bmi is an important predictor of the onset of mobility limitations .
older adults in the united states who gain weight over time have higher incidence of mobility limitations than those who maintain their weight .
large systematic reviews have shown that the relationship between bmi and mortality seems to follow a j - shaped ( sometimes u - shaped ) curve [ 17 , 2022 ] .
all - cause mortality appears to be lowest at bmi levels between 20 and 24.9  kg / m [ 20 , 22 ] , with obese individuals facing higher mortality risks than their normal - weight counterparts [ 20 , 22 , 23 ] .
recent studies , however , show that overweight individuals have higher life expectancy than individuals of normal weight or those who are obese , whereas other studies have an l - shape ( see , for a short review ) .
higher mortality at low levels of bmi has been associated primarily with lung cancer and respiratory diseases . at older ages , results from a systematic review and
meta - analysis indicated that bmi in the overweight range of 2529.9  kg / m is not associated with increased mortality , whereas other studies have shown that the burden of obesity on mortality seems to be reduced or eliminated among older adults [ 11 , 12 , 2630 ] .   the use of bmi categories has been criticized for not reproducing well the complexities of the bmi and mortality relationship [ 3133 ] .
gronniger   used semiparametric models and found that men in the mild - obese category ( bmis of 3035  kg / m ) had similar mortality than those of normal weight , but among women bmi levels above 27  kg / m were associated with higher mortality in the u.s .
wong and colleagues   used multivariable fractional polynomials to explore the association between bmi and mortality in a sample of adults in the ua they found that the best fitting model contained the powers 1 and 2 for bmi .
their results indicated that the nadir of the bmi mortality curve was in the normal range for women but overweight range for men .
zajacova and burgard   used generalized additive models and found that the nadir was at bmis 23 to 26 , which is also in the normal overweight range .
however , they point out that there are important differences depending on the cause of death . for example
, the association between bmi and diabetes mortality increases monotonically , but , for all - cause mortality , it followed more a v - shape .
however , even though these alternative models often provide better fit to the data , the results of these studies are often interpreted making references for traditional cutoffs as they are more easily understood by the general audience and health practitioners . the use of bmi and bmi categories have also been criticized because it can be related to underlying health status .
for example , individuals may be underweight based on their bmi because they have health conditions such as cancer , thyroid problems , infectious , or digestive diseases that lead to low body weight .
one approach to address this limitation has been to take into account body weight changes .
our study uses data a large cohort study conducted in so paulo , brazil , to examine the association between bmi and body weight changes on disability transitions and mortality , while controlling for a series of demographic , socioeconomic , and health determinants .
we investigate these associations on three types of disability ( activities of daily living , instrumental activities of daily living , and nagi 's limitations ) transitions .
data from the two waves ( 2000 and 2006 ) of the sabe cohort study conducted in so paulo , brazil , were used in this study .
sabe is a multicenter survey with respondents in seven major cities throughout lac countries that have been investigating the health and well - being of older adults ( age 60 and over ) .
the study was approved by the institutional review boards at the collaborating institutions [ 34 , 35 ] , and the participants provided consent to have their data used for research purposes .
the baseline sample was obtained using a two - stage stratified sampling based on the 1995 national household survey master sampling frame .
the first stage was a household interview conducted by a single interviewer using a standardized questionnaire that included several questions about the living conditions and health status of the subjects .
the second stage of data collection consisted of a household visit by a pair of interviewers who completed anthropometric and physical - performance measurements . at baseline ,
additional characteristics of the baseline data collection process have been described elsewhere [ 3638 ] . in 2006 , to reestablish contact , trained interviewers visited the addresses and neighborhoods of surviving participants from the 2000 survey . for those not found during these visits
, interviewers used the additional contact information collected at baseline ( e.g. , telephone numbers of children or other relatives ) to obtain further information about the subjects ' current location . in 2006 , researchers collected data via face - to - face interviews using a standardized questionnaire .
the 2006 questionnaire was very similar to the one used in 2000 but included additional questions that complemented the previous study .
vital statistics records were used to identify subjects who had died between 2000 and 2006 .
the search was based on the names , sex , dates of birth , and addresses listed in the 2000 database . of the 2,143 participants in the first wave of sabe so paulo , 355 ( 16.6% ) had missing data on selected variables .
those with missing data were older ( 75.1  years ) than those with complete data ( 72.9  years ) ( p = 0.0001 ) , but there were no sex differences .
the prevalence of all measures of disability was higher among those with missing data ( p < 0.001 ) .
the final sample is composed of 1,788 individuals , with a subset of 961 with weight change included in the analyses .
self - reported disability in six adl measures ( dressing , bathing , eating , getting in and out of a bed , toileting , and getting across a room ) were used to measure disability .
please tell me if you have any difficulty with these because of a health problem .
exclude any difficulties you expect to last less than three months .  after this introduction , they were asked  do you have difficulty  ?  and
 does not know ,  and  no response  for each one of the six adl measures .
participants who answered  does not know  and  no response  were classified as missing .
 the iadl items included were preparing a hot meal , managing money , shopping , using of transportation within the community , ability to use the telephone , and responsibility for one 's own medications .
 can not do it ,   does not know ,  and  no response .
 those who answered  can not do it  were classified as having difficulty performing the activity , whereas those answering  does not know  and  no response  were classified as missing . the nagi physical performance measure included lifting or carrying objects that weighed five kilograms or more ; lifting a coin ; pulling or pushing a large object , such as a living - room chair ; stooping , kneeling , or crouching ; and reaching or extending the arms above shoulder level . each of the three disability measures was converted into binary form , in which respondents scored  0  if they did not indicate any limitations and  1  if they reported having difficulty performing one or more activity in the scale .
body weight and height were measured without shoes and with light clothing by trained examiners .
four bmi categories were defined according to the criteria adopted by the pan american health organization for the sabe study : underweight ( bmi    23.0 ) , normal ( bmi  >  23 and <  28 ) , overweight ( bmi    28.0 and <  30 ) , and obese ( bmi    30 ) . change in bmi was calculated as bmi in 2006 minus the bmi at baseline .
this difference was divided by the baseline bmi and then recoded into three categories : ( a ) an increase of 5% or more ;
( b ) a decrease of 5% or more ; and ( c ) changes within 5% of the baseline weight ( reference category ) [ 19 , 39 ] .
the following sociodemographic characteristics were included in the analysis : age ( in years ) , gender , smoking status ( never , former , or current smoker ) , schooling ( in years of formal education ) , and household arrangement ( living alone or accompanied ) .
all regression analysis also included a measure of number of chronic conditions at the baseline .
health status based on the number of self - reported chronic conditions included diabetes , hypertension , cardiovascular disease , stroke , cancer , arthritis , and osteoporosis .  
12.1 for windows ( statacorp , college station , tx ) was used for all the statistical analyses .
weighted logistic regressions were then used to assess the influence of bmi on disability prevalence .
multinomial logistic regressions were used to assess the influence of bmi on disability transitions and mortality . for those free of disability ,
four outcomes were considered in the multinomial logistic regressions : remained free of disability ( reference category ) , became disabled ( incidence ) , died , or were lost to followup . for those who were disabled at the baseline , four outcomes were included in the multinomial logistic regressions : remained disabled ( reference category ) , recovered from disability , died , or were lost to followup .
multinomial logistic regressions were used to analyze the role of weight change on health transitions as discussed above , excluding mortality , as we do not have information on weight change prior to death in between waves .   in the baseline , there were 1,420 individuals free of adl and 368 individuals with adl . in 2006 , among those free of adl , 606 individuals had remained free of adl , 226 had developed adl , 329 had died , and 259 were lost in the followup or had missing data on adl status . among those who had adl in the baseline , 99 remained with adl , 75 recovered from adl , 144 died and 50 were lost in the followup or had missing data on adl in 2006 . for iadl limitations ,
1,207 were free of iadl , and 581 had iadl in the baseline . among those who were free of iadl in the baseline , 491 remained free of limitations , 257 developed iadl , 230 had died , and 229 were lost in the followup or had missing data on iadl in the second wave . among those with iadl in the baseline , 220 remained with iadl , 36 recovered from iadl , 243 had died , and 82 were lost in the followup or had missing data on iadl status in 2006 . regarding the nagi , 654 participants were free of it in 2000 , and 1,134 had at least one nagi limitation . among those free of nagi , 192 remained free of it , 210 developed nagi , 129 died , and 123 were lost in the followup or had missing data on the nagi variable in 2006 . among those who had at least one nagi limitation in 2000 , 539 remained with nagi 's limitations , 70 recovered from nagi 's limitations , 344 died , and 181 were lost in the followup or had missing data on nagi 's limitations in the second wave .
in the final sample , 23.4% were underweight , 43.3% had normal weight , 12.4% were overweight , and 21.1% of the participants were classified as obese .  
table 1 presents the prevalence estimates of disability according to measures of adl , iadl , and nagi 's limitations by sex and bmi category at baseline .
prevalence of adl and nagi 's limitations was highest among obese individuals , whereas prevalence of iadl was highest among underweight older adults .
weighted estimates indicated that 16.7% of the sample in so paulo had difficulty performing at least one adl .
prevalence of iadl reached 24.4% , and most ( 57.8% ) of the older brazilian adults reported nagi 's limitations . in logistic regressions , after adjusting for age and sex ( not shown ) , individuals who were underweight did not differ from those of normal weight on their likelihood of reporting having adl , iadl , or nagi in the baseline .
obese individuals were more likely than normal weight participants to report having at least one adl ( or = 1.8 , 95% ci = 1.2 , 2.6 ) and nagi 's limitations ( or = 2.5 , 95% ci = 1.8 , 3.6 ) .
there were no statistical differences between normal weight and obese participants regarding iadl prevalence at baseline .
there were no statistical differences between normal and overweight subjects regarding adl and iadl prevalence at baseline , but overweight individuals were more likely than those of normal weight to have nagi 's limitations ( or = 1.6 , 95% ci  =  1.1 , 2.2 ) .
women were more likely than men to report having adl , iadl , and nagi 's limitations at baseline ( p < 0.05 ) . 

table 2 shows the multinomial logistic regression results of the disability transitions and mortality between 2000 and 2006 among those who were free of disability in the baseline .
compared to normal weight individuals , obese individuals were more likely to develop adl ( rrr  =  2.1 ) and iadl ( rrr  =  2.4 ) , whereas individuals who were underweight were more likely to develop iadl ( rrr  =  1.9 ) .
mortality risks were higher among those who were overweight ( rrr  =  2.5 ) compared to those of normal weight in the nagi model in which the reference category was remaining free of nagi 's limitations .
for all measures of disability , the risk of becoming disabled increased with age . as expected ,
women were more likely to develop adl and nagi 's limitations , but not iadl , between waves .
higher number of chronic conditions was associated with higher mortality and higher incidence of adl and iadl .  

table 3 shows the multinomial logistic regression results of the disability transitions and mortality between 2000 and 2006 among those who had disability in the baseline .
being obese was also associated with lower recovery from nagi ( rrr = 0.46 ) versus remaining with at least one nagi limitation .
older age and higher number of chronic conditions were negatively associated with recovery . in the last set of analyses , we focus on the role of weight gain between waves on disability transitions ( table 4 ) .
the results presented in table 4 indicate that those who gained weight between waves were more likely to develop adl ( rrr  =  2.3 ) and nagi 's limitations ( rrr  =  2.2 ) than those who maintained their weight , even after controlling for initial bmi categories and other covariates .
women faced higher incidence of adl ( rrr  =  1.8 ) and nagi ( rrr  =  2.4 ) than men .
when the analyses focused on those who had disability in the baseline , we found that weight gain was associated with lower recovery from adl ( rrr  =  0.18 ) .
. a higher number of chronic conditions were associated with lower recovery of adl and nagi .
most previous studies have focused on the association between bmi and disability [ 4 , 9 , 13 , 15 , 16 ] or bmi and mortality [ 10 , 2029 , 3133 ] , but few have analyzed the effect of bmi on both disability and mortality [ 11 , 12 , 14 , 30 ] . using three disability measures and data from a large cohort study , this study contributes to the literature by exploring the impact of bmi and weight changes on disability status transitions and on mortality .
this study confirmed the negative effects of obesity on disability in so paulo , brazil .
higher levels of nagi 's limitations were also found among those who were overweight at baseline .
most longitudinal studies have found that obese older adults are more likely to have experienced incidence of disability in the followup than those of normal weight [ 13 , 14 , 40 ] , and our study confirmed these findings .
older adult brazilians who were obese at baseline faced higher risks of becoming disabled with adl or iadl limitations compared to those of normal weight .
however , being overweight was not associated with higher incidence of disability after controls were included in the analysis , which is consistent with previous findings . in terms of recovery , we also found that obese individuals were less likely to recover ( versus remaining disabled in the followup ) , as other studies have also found .
there is growing interest in the role of weight changes on health transitions [ 13 , 18 , 19 , 42 ] .
studies have shown that weight gain in older adults is associated with decreased physical function and role limitations [ 18 , 19 ] .
we found similar findings in which older adults who gained weight between waves were more likely to develop adl and nagi 's limitations than those who maintained their weight , even after controlling for initial bmi categories .
al snih and colleagues   also reported higher adl incidence among individuals who had weight gain of more than 5% between waves .
some studies have indicated that weight loss is associated with improvements in mobility and functioning , whereas others have reported increased adl disability .
weight - loss therapy among obese older adults seems to be beneficial for improving quality of life and physical functioning .
ritchie and colleagues   found that intentional weight loss was not associated with functional decline ; however , those who unintentionally lost weight faced higher rates of functional decline , regardless of the initial bmi . in our study , we found no differences between those who lost weight and those who maintained weight on disability transitions after controlling for initial bmi .
given the lack of data on intent related to weight changes , further studies are necessary to explore the impact of weight change on mortality and disability in latin american countries .
in additional analyses ( not shown and available upon request ) , we have explored additional models to test whether bmi and weight changes influence changes in the number of disabilities over time .
we found that obesity was associated with the increases in the number of nagi 's limitations .
weight loss and weight gain were associated with an increase in the number of adl and nagi 's limitations over time .
changes in the number of iadl limitations were not statistically associated with bmi categories or weight changes . as expected ,
older age was associated with the increases in the number of adl , iadl , and nagi 's limitations over time
. a higher number of chronic conditions were also associated with an increase in the number of adl , iadl and nagi 's limitations over time .
we also tested fractional polynomial models following the approach suggested by wong and colleagues   to examine the relationship between bmi , disability and mortality ( results available upon request ) , and our main conclusions remain the same , which indicates that findings are robust to different model specifications .  
the only mortality differential by bmi categories was found among overweight participants who were more likely to die than to remain free of nagi 's limitations . in further analyses ( not shown ) , results from a logistic regression that controlled for the same covariates included in this study , revealed no differences in mortality among underweight , normal weight , overweight , and obese participants .
this is consistent with previous studies suggesting that the association between bmi and mortality becomes less u - shaped at older ages , and others that suggest that higher bmi may not be detrimental for mortality at older ages .
monteverde and colleagues   also did not find statistical differences in mortality among older adults between higher bmi categories ( overweight and obese ) and normal subjects when using traditional bmi cutoffs , though they reported statistical differences when bmi was categorized in relative terms .
however , some studies allude to the fact that the association between bmi and mortality is differential between individuals who are healthy versus those with chronic conditions .
the obesity paradox literature indicates that excess weight is actually protective among patients with chronic disease . in our sample , there were no mortality differentials by bmi categories among those with chronic conditions , but overweight individuals free of chronic conditions had lower mortality than those of normal weight ( results available upon request ) .  
our findings also contribute to a growing debate in the field about whether greater life expectancy implies better health for the expanding surviving elderly female population in latin america [ 37 , 4651 ] .
we found that brazilian women experience higher levels of disability than men , which is consistent with previous studies [ 52 , 53 ] .
previous studies have indicated that brazilian women face lower mortality than their male counterparts [ 37 , 54 ] , and this study confirms these findings .  
aging is related to the increase of fat mass , and there is growing evidence of the detrimental impact of obesity on disability at older ages .
there is evidence as well that changes in lifestyle , such as walking , have positive effects on preventing mobility limitations .
a large proportion of older adults , however , do not engage in physical activity . in a study based on an urban sample in brazil , for example , 71% of older adults reported living sedentary lives . when asked about neighborhood characteristics related to concerns of leaving home to go out ,
most ( 78% ) reported fear of being robbed , while almost half ( 48.2% ) said that they were afraid of falling because of sidewalk defects .
fear of falling due to poor sidewalk conditions was associated with a 62% increase in the expected number of adl conditions .
therefore , investments aimed at improving urban infrastructure and safety may be effective in addressing the health conditions of older adults in brazil .
this study advances the literature on the impact of body weight and body weight changes on disability and mortality .
first , the data used in the study on disability measures were self - reported .
although this could be a possible source of bias , methodological studies have shown that self - reported data on functional disability are consistent with medical diagnoses .
second , the use of bmi as a measure for body weight composition among older adults is very controversial as it does not take into account body fat distribution .
in addition , bmi at baseline can be associated with health status [ 16 , 17 ] .
therefore , it is important to control for weight changes , which we accomplished in this study .
some authors have argued that waist circumference or waist - to - hip ratio could be better predictors of disability and mortality ; however , most studies to date have focused on the use of bmi and the categories used here .
other scholars have indicated that , at least for developed countries , information on bmi , waist circumference , or waist - to - hip ratio do not necessarily improve prediction of mortality due to cardiovascular disease ; instead , they suggest using information on systolic blood pressure , diabetes status , and lipids when those are available .
waist circumference and waist - to - hip ratio can be useful in better understanding mortality risks [ 59 , 60 ] . in brazil , as in other developing countries , data on blood pressure and
lipids are often lacking , so the use of anthropometric measures , such as waist circumference , may improve our understanding of the impact of body composition changes on mortality and disability .
third , the first wave of sabe focuses on the civilian population not residing in institutions . as a result
, estimates may be biased if one expects institutionalized individuals , particularly those residing in nursing homes , to be more likely to have a higher prevalence of disability than the noninstitutionalized population .
however , because the institutionalized population in brazil is relatively small , this possible bias is likely not to be very significant .
this study confirms previous studies that have found obesity to be associated with increased disability in brazilian older adults .
historically , brazil has mainly been concerned with curbing malnutrition ; however , in recent years , new policies have targeted the marketing of highly processed and unhealthy foods .
owing to the fact that obesity rates in brazil have been increasing drastically for the past three decades , our findings have important implications for policy makers in brazil with regard to curbing disability risk by promoting the use of effective preventive measures to reduce body weight , thereby making healthy aging a reality .
 the aim of this study was to examine the association between body mass index and weight changes on disability transitions and mortality among brazilian older adults . 
 longitudinal data from the health , well - being , and aging in latin america and the caribbean study conducted in so paulo , brazil ( 2000 and 2006 ) , were used to examine the impact of obesity on disability and mortality and of weight changes on health transitions related to disability . 
 logistic and multinomial regression models were used in the analyses . 
 individuals who were obese were more likely than those of normal weight to have limitations on activities of daily living ( adl ) , instrumental activity of daily living ( iadl ) , and nagi 's limitations . 
 obesity was associated with higher incidence of adl and iadl limitations and with lower recovery from nagi 's limitations . 
 compared to those who maintained their weight , those who gained weight experienced higher incidence of adl and nagi 's limitations , even after controlling for initial body mass index . 
 higher mortality among overweight individuals was only found when the reference category was  remaining free of nagi limitations .  
 the findings of the study underline the importance of maintaining normal weight for preventing disability at older ages . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusion