the beijing longitudinal study of aging is a prospective cohort study of 3,257 community - dwelling chinese population aged 55 years and older at baseline .
the geographic distribution , economic status , age , and education of the sample represent the older population of beijing , as obtained from the fourth national census data ( 27 ) . as described elsewhere (
27,28 ) , the cohort was assembled in 1992 ; the response rate was 91.2% ; participants were followed every 23 years . at the time of the 1997 survey , 784 subjects ( 24.1% ) had died , and 430 were missing at follow - up .
the survey was based on self - reporting information that covered demographic characteristics , socioeconomic status , activities of daily living , lifestyle , physical health , psychological and self - rated health , medical conditions , cognitive status , and the use of health care services . trained interviewers , mostly nurses or physicians , administered a standard questionnaire at the respondent s home ; where available , medical records were used to verify the presence of disease .
depressive symptoms were evaluated using the center for epidemiologic studies  depression scale , and cognitive function was assessed using the mini - mental state examination ( mmse ) scale . for this secondary analysis ,
survival status was determined through interviews with surviving household members and/or neighbors and verified by death certificates and/or local police register records .
vital status was known for 91.6% of the participants , with censoring for dates of death or dropout .
data of the subjects ( 8.4% ) with missing survival information were excluded from survival - related analysis only .
an fi was constructed using the baseline survey data ( 1992 ) for each participant ( n = 3,257 ) as described in the previous reports ( 14 , 26 ) .
specifically , each variable used in the fi satisfied the criteria of being associated with health status , accumulating with age , not saturating ( ie , not becoming present in > 80% of people ) , having more than 1% prevalence and less than 5% missing , and covering several systems ( 29 ) . as a result ,
35 variables were included , containing diseases ( n = 8) , symptoms ( n = 7 ) , psychological problems ( n = 5 ) , basic and instrumental activities of daily living disabilities ( n = 14 ) , the mmse total score ( table1 ) .
fifteen of these variables were binary , in which  0  was used to indicate the absence of the deficit and  1  to indicate its presence . for
the remaining 20 , three level variables , an additional value of 0.5 represented the intermediate status such as  sometimes  .
the mmse was coded as 0 ( mmse  24 ) , 0.5 ( mmse = 1523 ) , and 1 ( mmse  14 ) .
next , all the variables were summed and divided by 35 to yield a fi ranging from a theoretical minimum of 0 ( no deficits present ) to a possible maximum of 1.0 ( all deficits present ) , with higher fi values representing a greater level of frailty and thus worse health and greater vulnerability to adverse outcomes . for individuals in whom a given variable was missing ,
the fi was calculated based on the items present ; variables with missing values were excluded from both the numerator and the denominator . in this study ,
the maximum number of missing values in any individual fi was never greater than 1 .
sample characteristics were described using means and standard deviations for interval variables and percentages for the categorical variables , with differences tested using analysis of variance and chi square (  ) , respectively .
the attributable risk was calculated for each variable as the fraction referring to the proportion of risk among the exposed population that could be attributed to the exposure ( 30 ) .
the fi values were calculated separately for men and women and for different age groups .
the 95% and 99% submaximal fis ( ie , the 95% and 99% fi limits ) for a given age group were calculated as the mean fi values of the 5% and the 1% people with the greatest fi at the ages .
multivariable regression analysis was used to examine the relationship between the fi ( mean and limit values ) with age and mortality .
five - year mortality rates were compared between men and women using student s t tests , whereas the survival probability was evaluated using the kaplan 
the beijing longitudinal study of aging is a prospective cohort study of 3,257 community - dwelling chinese population aged 55 years and older at baseline .
the geographic distribution , economic status , age , and education of the sample represent the older population of beijing , as obtained from the fourth national census data ( 27 ) . as described elsewhere (
27,28 ) , the cohort was assembled in 1992 ; the response rate was 91.2% ; participants were followed every 23 years . at the time of the 1997 survey , 784 subjects ( 24.1% ) had died , and 430 were missing at follow - up .
the survey was based on self - reporting information that covered demographic characteristics , socioeconomic status , activities of daily living , lifestyle , physical health , psychological and self - rated health , medical conditions , cognitive status , and the use of health care services . trained interviewers , mostly nurses or physicians , administered a standard questionnaire at the respondent s home ; where available , medical records were used to verify the presence of disease .
depressive symptoms were evaluated using the center for epidemiologic studies  depression scale , and cognitive function was assessed using the mini - mental state examination ( mmse ) scale . for this secondary analysis ,
survival status was determined through interviews with surviving household members and/or neighbors and verified by death certificates and/or local police register records .
vital status was known for 91.6% of the participants , with censoring for dates of death or dropout .
data of the subjects ( 8.4% ) with missing survival information were excluded from survival - related analysis only .
an fi was constructed using the baseline survey data ( 1992 ) for each participant ( n = 3,257 ) as described in the previous reports ( 14 , 26 ) .
specifically , each variable used in the fi satisfied the criteria of being associated with health status , accumulating with age , not saturating ( ie , not becoming present in > 80% of people ) , having more than 1% prevalence and less than 5% missing , and covering several systems ( 29 ) . as a result ,
35 variables were included , containing diseases ( n = 8) , symptoms ( n = 7 ) , psychological problems ( n = 5 ) , basic and instrumental activities of daily living disabilities ( n = 14 ) , the mmse total score ( table1 ) . fifteen of these variables were binary , in which  0  was used to indicate the absence of the deficit and  1  to indicate its presence . for
the remaining 20 , three level variables , an additional value of 0.5 represented the intermediate status such as  sometimes  .
the mmse was coded as 0 ( mmse  24 ) , 0.5 ( mmse = 1523 ) , and 1 ( mmse  14 ) .
next , all the variables were summed and divided by 35 to yield a fi ranging from a theoretical minimum of 0 ( no deficits present ) to a possible maximum of 1.0 ( all deficits present ) , with higher fi values representing a greater level of frailty and thus worse health and greater vulnerability to adverse outcomes . for individuals in whom a given variable was missing ,
the fi was calculated based on the items present ; variables with missing values were excluded from both the numerator and the denominator . in this study ,
the maximum number of missing values in any individual fi was never greater than 1 .
sample characteristics were described using means and standard deviations for interval variables and percentages for the categorical variables , with differences tested using analysis of variance and chi square (  ) , respectively .
the attributable risk was calculated for each variable as the fraction referring to the proportion of risk among the exposed population that could be attributed to the exposure ( 30 ) .
the fi values were calculated separately for men and women and for different age groups .
the 95% and 99% submaximal fis ( ie , the 95% and 99% fi limits ) for a given age group were calculated as the mean fi values of the 5% and the 1% people with the greatest fi at the ages .
multivariable regression analysis was used to examine the relationship between the fi ( mean and limit values ) with age and mortality .
five - year mortality rates were compared between men and women using student s t tests , whereas the survival probability was evaluated using the kaplan  meier analysis .
women were also more likely to have problems with function , cognition , and depression and to exercise less , especially after age 65 . in the 55- to 64-year - old group ,
however , women aged 65 + years showed better performance with items of both activities of daily living and instrumental activities of daily living compared with men of the same age . of note , women who were between 5564 years appeared to take more medication compared with older women or men .
considering the individual deficits that make up the fi , women were more likely than men to report most deficits , except for stroke and several function items ( table 2 ) .
the baseline demographic and health conditions did not differ significantly between the participants ( n = 275 , 8.4% ) who missed survival information and the rest of the sample regarding mean age ( 70.9  9.2 vs 70.1  9.0 , f = 2.19 , p = .14 ) , % female ( 53.5% vs.50.9% ,  = 0.67 , p = .41 ) , % married ( 62.9% vs 65.7% ,  = 0.850 , p = .36 ) , mean mmse ( 23.6  4.1 vs 23.1  4.3 , f = 1.88 ,   p = .17 ) , or the mean level of fi ( 0.12  0.10 vs 0.13  0.10 , f = 0.14 , p = .71 ) ; however , the latter were more likely to be better educated and live in an urban dwelling ( 9 + y education = 22.9% vs 11.5% , =30.26 , p < .001 and rural dwelling : 12.0% vs 36.5% ,  = 66.98 , p < .001 ) .
demographics and characteristics of middle - aged and older adult men and women in the sample of the beijing longitudinal study of aging 
 note : data are presented as mean  standard deviation , unless specified otherwise .
adl = activities of daily living ; iadl = instrumental activities of daily living ; mmse = mini - mental state estimation ; ces - d = center for epidemiologic studies  depression .
group differences were examined using analysis of variance ( f ) and  test , respectively , for interval and categorical variables . the level of significance ( p )
percentage present of the health deficits used in constructing the frailty index , and their attributable risks for 5-year mortality , in middle - aged and older adult men and women 
 note : ar = attributable risk ; tia = transient ischemic attack ; mmse = mini - mental state estimation .
the level of significance ( p ) was set at .05 . in both men and women ,
most deficits were associated with an increased risk of mortality by 5 years ( table 2 ) . for the 55- to 64-year - old group , many deficits appeared to be more lethal for women than for men .
this was in contrast to those aged 65 + years : the deficits often showed a higher risk for death in men than in women .
notably , several items , when considered individually , seemed to have a protective effect regarding the 5-year mortality in the 65 + years group ( ie , negative attributable risk ) .
such variables included using hearing aids , having arthritis , transient ischemic attack , and thyroid disease , which most likely were treated .
considering deficits collectively , the mean fi increased with age for both men and women ( figure 1a and b ) .
the minimum fi remained to be 0 at almost all ages , except for ages above 80 years ( minimum fi = 0.003 ) . for any age group ,
the mean fi was greater in women than in men ( f = 67.87 , p < .001 for the difference in the means ; figure 1a and b ) .
the 95% limit values of the fi also increased with age , similarly in men and women .
the 99% submaximal limit to the fi showed no correlation with age above the age of 60 years in men , and above the age of 65 years in women ( figure 1a and b ) .
the 99% limit fi value was significantly higher in women ( 0.52  0.04 ) than in men ( 0.44  0.02).the highest absolute fi value was 0.61 in men and 0.69 in women ( ie , not exceeded 0.7 ) .
frailty index ( fi ) as a function of age in men ( panel a ) and in women ( panel b ) .
the level of fi was calculated for each individual as the sum of deficits present in the individual divided by 35the total number of variables considered .
the 95% and 99% frailty limits for a given age group were calculated as the mean fi values of the 5% ( squares and dashed lines ) and the 1% ( triangles and solid lines ) of people with the highest fis , respectively .
the mean death rate was higher in men than in women ( t = 3.74 , p = .010 ) and increased with age for both men and women ( figure 2a and b ) . for the people in whom the fi was higher than the 95% limit , the death rates were high and did not differ between men and women ( n = 94 vs n = 91 ; t = 0.54 , p = .610 ) ; this was also the case regarding the 99% limits ( n = 28 men and 28 women ; t = 0.10 , p = .922 ; figure 3a and b ) .
all but one person aged 65 + years who had an fi at or above the 99% limit died in 5 years ( ie , 15/16 men with a mean fi = 0.46  0.04 and 14/14 women with the mean fi = 0.54  0.05 ) . in the 17 people younger than 65 years who had very high fis , the 5-year mortality rates were closer to 50% and none survived to age 79 .
death rates in relation to the frailty index ( fi ) in men ( panel a ) and in women ( panel b ) .
the level of fi was calculated for each individual as the sum of deficits present in the individual divided by 35the total number of variables considered .
mean fis ( light - gray bars ) were calculated as the average of the fi values of all people within the given age groups .
the 95% and 99% frailty limits for a given age group were calculated as the mean fi values of the 5% ( medium - gray bars ) and the 1% ( dark - gray bars ) people with the highest fis , respectively .
five - year survival probabilities for men ( panel a ) and women ( panel b ) calculated using the kaplan
data are presented for people with a frailty index ( fi )  0.03 ( ie , the most fit people ; dashed lines ) and those with a fi above the 99% limit of the fi ( ie , the least fit people in various age groups ; solid lines ) . for men , the 99% limit was 0.61 ; for women , it was 0.69 .
in this study , we evaluated the limit of frailty in chinese men and women by applying the deficit accumulation approach and linked it to short - term mortality .
an fi was constructed using 35 variables assessing a wide range of health measures including medical history and disease conditions , signs , symptoms , psychological and cognitive health , and functions of daily living .
the performance of the fi with age and the increased mortality with the fi were consistent with previous reports using the same and many other data sets ( 11,1517 ) .
our study confirmed that limits to frailty were present in this chinese older adult sample , and further extended the fi limit analysis to include people of late middle ages .
this is the first study to identify a gender difference in frailty limit in relation to healthy life expectancy and mortality .
our data suggest that the gender difference regarding the limit of how many deficits one can have has impact on the gender difference in mortality .
consistent with other studies ( 17,18,31 ) , here women showed more deficit accumulation than men .
meanwhile , women , especially those with more advanced age , were more likely to have depression and lower cognitive performance . here
, men aged 5564 reported greater activities of daily living performance than women ; the situation was reversed above age 65 .
gender interaction in how deficits affect disability has not been well studied and warrants further research using different data sets . as expected , having many deficits increased the risk of death ( table 2 ) .
even so , and curiously , some apparent deficits ( eg , using hearing aids , having arthritis , transient ischemic attack , and thyroid disease ) were associated with better 5-year survival .
first , certain mild deficits ( eg , transient ischemic attack ) are indicators of subsequent severe damage ( eg , stroke ) , and their early treatment might prevent more severe problems that otherwise would lead to death .
second , for some chronic diseases , such as arthritis and thyroid illness , medication intake ( especially , nonsteroidal anti - inflammatory drugs ( 32 ) and perhaps also allopurinol ) ( 33,34 ) might help to prevent the occurrence to other deficits such as inflammation and metabolic syndromes .
third , intervention strategies such as hearing aids and dentures prevent declines in health , as have better social conditions and better nutrition . on the other hand
, the use of dentures and hearing aids might be surrogates for better overall access to health care services .
some factors , such as an apparently protective effect of arthritis , have been seen in other studies ( 35,36 ) , including more vulnerable population of disabled individuals ( 37 ) .
likewise , the impact of positive self - rated health is widely known although correcting for frailty status seems to allow additional insight  that is , self - rated health is more explanatory in relatively fit than in relatively frail people ( 38 ) .
even so , commenting on specific factors that might be associated with better conditions is problematic due to the effect of multiple comparisons and confounding .
our data suggest that in general , women tolerate more health problems than men do and some of the items showed an apparent protective effect only in women .
the advantage in health expectancy in women was clearer in those aged 65 years or older , even though women enjoyed a lower mortality rate than men at all ages ( figure 2 ) .
an empirical 99% fi limit of approximately 0.70 was seen in women , as reported in previous analyses that do not separate limit by sex ( 18,19 ) .
in fact , as shown here , the empirical 99% fi limit of men was notably lower than 0.7 . in consequence , at the 99% limit
, women tended to be frailer only at more advanced ages , while more men with a similar level of frailty ( eg , fi 
  0.45 ) would have already died .
the argument seems to be supported by the data showing the near - zero slope of deficit accumulation at the submaximal limit in relation to age in the older men , indicating an earlier exhaustion of redundancy in men than in women in this chinese sample . at the 99% frailty limit , little difference in mortality rates
were found between men and women at this limit while the maximum ( 100% ) death rate was approached .
this result is consistent with the theory of reliability , stating that at the frailty limit , a system can age no more and little chance of survival can be expected ( 20 ) . here ,
when approaching redundancy exhaustion , men were more susceptible to death than women , with highest mortality reached independent of age .
at the point when the redundancy exhaustion was reached in women , neither differential gender nor age effect on mortality was observed , as nearly all at the frailty limit were subjected to death .
taken together , the question as to why frailer women live longer than men even in the poorest countries in the world ( 25 ) can be partially revealed by our data . even though women at any given age tended to have more deficits than men , their level of tolerance of these deficits , as measured by the limit to the fi , was greater than men . in consequence ,
the average death rate of women was significantly lower than that of men at any given age .
the maximum death rate ( 100% ) was seen in men with much lower fi values than those in women of the same age .
compensation for mortality  than men , providing a likely explanation for the worldwide observation that frailer women outlive healthier men ( 31 ) .
all the variables used to construct the fi were based on self - reported data , the accuracy of which might not be the same as a clinical assessment .
interindividual variability in respect to health care access may be reflected in population survey data , which may be especially true in china where significant regional socioeconomic and health care differences have been reported ( 39 ) .
future work on studying frailty limits considering gender disparity in clinical settings will be of particular interest .
also , our data set was based on the health assessments in 1992 , which likely bears variations to the current status in china . unlike the west , fast economic growth in china has brought dramatic changes in education , income , lifestyle , culture , and health care in the past two decades , which likely has influenced the level of health measures and thus the fi ( 40 ) .
recent interventions , such as protein - energy supplementation to prevent functional decline in frail older adults , would not be reflected in these data ( 41 ) . despite high demand for health care improvement
even so , consistent results regarding the fi values , relationships of fi with age , and gender disparity in the mean fi values were suggested by our study .
these results are consistent with previous publications ( 11,1519 ) and in support of the findings on frailty limit ( 14,19,26,43 ) . in conclusion
, this study suggests a gender difference in frailty limits and its relationship with short - term mortality in older adults .
the highest fi values were significantly lower and emerged earlier in men than in women ; in both , the highest mortality resulted .
these results have important implications for understanding health expectancy and risk of death in the older population , as well as the evolution of the gender differences in frailty , which might start in midlife ( 44 ) .
quantification of frailty limits by taking into account gender differences can benefit public health planning and clinical decision making , for example , implementing frailty into clinical practice to achieve modifiable intervention outcomes ( 45 ) , for better care of older patients .
the research was supported by a canadian institute of health research grant under the china - canada joint health research initiative program ( cci-92216 ) .
k.r . accepted support from dalhousie university medical health foundation as the kathryn walden alzheimer s research chair .
 background.on average , as people age , they accumulate more health deficits and have an increased risk of death . 
 the deficit accumulation  based frailty index ( fi ) can quantify health and its outcomes in aging . 
 previous studies have suggested that women show higher fi values than men and that the highest fi score ( the  limit to frailty  ) occurs at a value of fi ~ 0.7 . 
 even so , gender differences in the limit to frailty have not been reported.methods.data for this analysis were obtained from the beijing longitudinal study of aging that involved 3,257 community - dwelling chinese people , aged 55 + years at baseline . 
 the main outcome measure was 5-year mortality . 
 an fi consisting of 35 health - related variables was constructed . 
 the absolute and 99% fi limits were calculated for different age groups and analyzed by sex.results.the mean level of the fi increased with age and was lower in men than in women ( f = 67.87 , p < .001 ) . 
 the 99% fi limit leveled off slightly earlier with a relatively lower value in men ( 60 years ; 0.44  0.02 ) compared with that in women ( 65 years ; 0.52  0.04 ) . 
 the highest absolute fi value was 0.61 in men and 0.69 in women . in both groups , people with an fi greater than or equal to 
 the 99% limit showed close to 100% mortality by 5 years.conclusion.compared with men , women appeared to better tolerate deficits in health , yielding both relatively lower mortality and higher limit values to the fi . 
 even so , the fi did not exceed 0.7 in any individual . 
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Participants and Data
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Statistical Analysis
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