Disability-Free Life-Years LostAmong Adults Aged$50 Years,With and Without DiabetesDOI: 10.2337/dc15-1095

OBJECTIVE

Quantify the impact of diabetes status on healthy and disabled years of life forolder adults in the U.S. and provide a baseline from which to evaluate ongoingnational public health efforts to prevent and control diabetes and disability.

RESEARCH DESIGN AND METHODS

Adults (n = 20,008) aged 50 years and olderwere followed from 1998 to 2012 in theHealth and Retirement Study, a prospective biannual survey of a nationally rep-resentative sample of adults. Diabetes and disability status (defined by mobilityloss, difficulty with instrumental activities of daily living [IADL], and/or difficultywith activities of daily living [ADL]) were self-reported. We estimated incidence ofdisability, remission to nondisability, andmortality.We developed a discrete-timeMarkov simulation model with a 1-year transition cycle to predict and comparelifetime disability-related outcomes between people with and without diabetes.Data represent the U.S. population in 1998.

RESULTS

From age 50, adults with diabetes died 4.6 years earlier, developed disability 6–7years earlier, and spent about 1–2 more years in a disabled state than adultswithout diabetes. With increasing baseline age, diabetes was associated withsignificant (P < 0.05) reductions in the number of total and disability-free life-years, but the absolute difference in years between those with and without di-abetes was less than at younger baseline age. Men with diabetes spent abouttwice as much of their remaining years disabled (20–24% of remaining life acrossthe three disability definitions) asmenwithout diabetes (12–16% of remaining lifeacross the three disability definitions). Similar associations between diabetesstatus and disability-free and disabled years were observed among women.

CONCLUSIONS

Diabetes is associated with a substantial reduction in nondisabled years, to agreater extent than the reduction of longevity.

Diabetes is one of the most common public health threats in the U.S., affecting 12%of adults and carrying an estimated lifetime probability of 40% (1,2). Furthermore,increases in life expectancy of the diabetes population have led to a large increase inthe number of years spent with diabetes for the average person (1). This, combinedwith increased prevalence since 1985, has led to a 156% and 70% increase in thenumber of years that a typical community of men and women, respectively, willspend with diabetes (1).

1Division of Diabetes Translation, Centers for Dis-ease Control and Prevention, Atlanta, GA2Immunization Safety Office, Centers for DiseaseControl and Prevention, Atlanta, GA3Merck & Co., North Wales, PA4Hubert Department of Global Health, RollinsSchool of Public Health, Emory University, At-lanta, GA

Corresponding author: Barbara Bardenheier,bfb7@cdc.gov.

Received 22May 2015 and accepted 2 November2015.

This article contains Supplementary Data onlineat http://care.diabetesjournals.org/lookup/suppl/doi:10.2337/dc15-1095/-/DC1.

B.H.B. is currently affiliated with the Immuniza-tion Safety Office, National Center for Emergingand Zoonotic Infectious Diseases, Centers for Dis-ease Control and Prevention, Atlanta, GA.

The findings and conclusions in this report arethose of the authors and do not necessarily rep-resent the official position of the Centers for Dis-ease Control and Prevention.

© 2015 by the American Diabetes Association.Readersmayuse this article as longas thework isproperly cited, the use is educational and not forprofit, and the work is not altered.

Barbara H. Bardenheier,1,2 Ji Lin,1

Xiaohui Zhuo,1,3 Mohammed K. Ali,4

Theodore J. Thompson,1 Yiling J. Cheng,1

and Edward W. Gregg1

Diabetes Care 1

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Diabetes is known for its diverse vas-cular and neuropathic complicationsand for the associated excess risk of dis-ability. Disability experienced amongpeople with diabetes includes loss ofmobility and the ability to carry out in-strumental and basic activities of dailyliving (3–6). The increased risk of dis-ability erodes quality of life, increasesmorbidity, and increases the need forhealth services and social security re-sources, relative to peers without dia-betes (7). Disability-free life-years is ameasure of population health thatquantifies the impact of health condi-tions on nondisabled and disabled years(8). As such, it provides an importantmetric to gauge the impact of chronicconditions, as well as attempts of publichealth interventions to compress mor-bidity in the population alongside re-ductions in mortality.Despite the well-documented impact

of diabetes on diverse forms of macro-vascular morbidity (9) and mortality(10), there have been no national esti-mates of the years of disability-freeversus disabled life-years lost to thedisease among U.S. adults. In theseanalyses, we assembled prospectivecohort data on incidence of disabilityand mortality among a diverse, popula-tion-based sample of U.S. adults aged$50 years to quantify the impact of di-abetes on disability-free and disabledyears of life and to provide a baselinefrom which to evaluate the impact ofnational public health efforts to controland prevent diabetes.

RESEARCH DESIGN AND METHODS

Population and Data SourcesOur analyses are based on 20,008 adultsaged 50 and older enrolled in the HealthandRetirement Study (HRS), a population-based longitudinal cohort study (11). Re-spondents entered in 1998 with biennialvisits in 2000, 2002, 2004, 2006, 2008,2010, and 2012. Initial response ratesranged from 69% to 81%, and follow-upresponse rates were 87% to 89% (12).Reports from the eight visits, describedbelow, were used to estimate prevalenceand incidence of diabetes, incidence ofdisability, mortality, and incidence tran-sitions from diabetes and nondiabetesstatus to disability andmortality, as wellas remission from disability to nondis-abled states and mortality. The HRS issponsored by the National Institute on

Aging and performed by the Institutefor Social Research at the University ofMichigan. The Health Sciences Institu-tional Review Board at the Universityof Michigan approved the HRS study de-sign. The data used for this analysiswere stripped of unique personal iden-tifiers and are publicly available. Thedata used for our analyses are nation-ally representative.

DefinitionsPrevalent diabetes was defined by thesurvey question of whether the individ-ual had been diagnosed by a physicianwith diabetes or high blood glucose. In-cident diabetes was defined as the firstself-report by a respondent to HRS of adiabetes diagnosis (i.e., being told by adoctor that he or she has diabetes orhigh blood glucose) during the study pe-riod (13). Incident diabetes cases wereincorporated into analyses such that anindividual who was diagnosed with di-abetes after baseline was included inthe diabetes group only if they did notbecome disabled prior to a diabetes di-agnosis. If they became disabled afterthey were diagnosed with diabetes,they were considered an incident caseof disability in the diabetes group.

Mobility disability was defined asself-report of difficulty with any of thefollowing: walking one block; climbingone flight of stairs; stooping, crouching,or kneeling; and pushing or pulling alarge object (14). Modifying a previ-ously developed four-state model fordefining mobility disability among peo-ple with diabetes (14), we classified arespondent’s mobility disability as se-vere if they reported four or five ofthe previously mentioned mobilitymeasures. Similarly, instrumental activ-ities of daily living (IADL) were definedas self-report of difficulty doing any ofthe following: using the telephone, tak-ing medication, handling money, shop-ping, and preparing meals. Activities ofdaily living (ADL) were defined as self-report of difficulty doing any of the fol-lowing: walking across a room, gettingin and out of bed, dressing, bathing, andeating. Death was determined duringexit interviews with the respondent’sproxy, family, or friend, and confirmedas valid by the National Center for HealthStatistics via linkage to theNational DeathIndex (12). The year of death reportedduring the exit interview was used for

censoring at time of death. If year wasunknown, year of exit interview wasused (n = 126, 7%).

Estimation of IncidenceAge-specific incidence of mobility, ADL,and IADL was modeled using general-ized estimating equations with a binaryoutcome, wherein people with preva-lent disability at baseline were ex-cluded. All the regression models werestratified by sex and included age,piecewise age function, race/ethnicity,and diabetes status. Data were mod-eled with STATA version 13 (StataCorp,College Station, TX), which accounts forthe longitudinal complex survey design.Estimates were weighted to the U.S.population in 1998, followed through2012. Regression estimates were usedto determine the probability of incidentdisability among those with and with-out diabetes by age. We were unableto further stratify on race/ethnicitydue to the small sample size. Thereforewe adjusted for race/ethnicity by cen-tering individual responses around thegrand mean. Thus, our primary findingsare adjusted for the proportion of re-spondents by race/ethnicity. We con-ducted additional analyses adjustingfor the prevalence of cardiovasculardisease (CVD) to determine its effectson the primary outcomes (incidence,remission, and mortality) affectinghealthy life-years. These probabilitieswere used as inputs to the Markov mod-els. Similarly, probability of remissionfrom disability was calculated on a yearlybasis as the people with incident disabil-ity (for mobility, IADL, and/or ADL, re-spectively) who return to a state ofnondisablement.

Modeling ApproachWe developed a discrete-time Markovcohort simulation model with annualtransition to predict and compare life-time disability-related outcomes be-tween people with and without diabetesfrom age 50 through 100 (Fig. 1) (15).The model has five states: not disabled,short-term disability, not disabled butwith previous disability, permanent dis-ability, and death. Each year, the specificproportion that moves between states(i.e., transition probabilities) was deter-mined by the regression models.

We created states of short-term dis-ability and not being disabled but with

2 Disability-Free Life-Years and Diabetes Diabetes Care

disability history (i.e., recovered fromdisability) as two bridge states (i.e., con-nections between states) because of thehigh remission rates (returning to non-disabled states) observed in the data.Moreover, to simplify the model, thestate of short-term disability is definedas being disabled and having no remis-sion by the end of the 1st year of disabil-ity onset. Therefore, in the model, aperson with disability onset will eitherrecover or move to the state of perma-nent disability in the next year. The as-sumption is supported by the fact thatfew remissions occurred later in thestudy. Further, like those in the studypopulation, individuals may have multi-ple episodes of short-term disabilityover their lifetime in the model.On the basis of the model, we pre-

dicted three disability-related outcomes,including the remaining lifetime risk ofbecoming disabled, average age of dis-ability onset, and remaining life-yearsliving with and without disability,among adults who reported havingand not having diabetes at ages 50,60, 70, and 80. Remaining lifetimerisk was calculated as the cumulativerisk of experiencing short-term or per-manent disability over a lifetime. Be-cause of the high frequency of multipleepisodes of short-term disability, theaverage age of onset was defined asthe difference between the life expec-tancy and mean disability-free life-years. For example, from a baselineage of 50, it is possible to become dis-abled at age 56, recover at 58, and thenbecome disabled again at age 64.Therefore the average age of onsetwas defined by taking the differencebetween life expectancy from age 50,and the average number of disability-free life-years remaining, instead of

choosing the age of onset of oneof the disabled episodes. The CIs andP values of the lifetime estimates wereestimated using a Monte Carlo simula-tion of the Markov model with transi-tion probabilities sampled from thepreviously described regression mod-els. Five thousand runs were per-formed for each group with or withoutdiabetes.

RESULTS

Study Population CharacteristicsAmong the 20,008 respondents in theanalytic sample, age ranged from 50 to105, and baseline diabetes prevalencewas 14.1% among men and 12.2%among women. Among both sexes,;15–17% of the population was non-white and 22–23% was obese. (Table 1)Among those with a diabetes diagnosisat baseline, 8.7% were taking insulinand oral medication, 52.4% were takingoral medication only, 17.1% were tak-ing insulin only, and 21.7% were takingno antidiabetic medications. The vastmajority of all respondents who report-ed they had high blood pressure atbaseline reported they were takingmedication for high blood pressure(those with diabetes, 87%; those with-out diabetes, 81%).

Incidence of Diabetes, Disability, andMortalityEstimated incidence of diabetes was1.5% per year among men and 1.3%per year among women. Annual inci-dence of severe mobility disability in-creased with age from absolute levelsof 0.4% in men and 0.6% in women atage 50, roughly doubling in incidence byage 60, quadrupling by age 68, and thenincreased 20 times by age 87 (data notshown). Compared with severe mobility

disability, incidence of IADL and ADLdisability increased similarly from age50 to 68 and increased 26 times forwomen and 27 times for men by age87. Among both men and women, dis-ability rates (mobility, IADL, and ADL)were one and a half to two times higheramong people with diabetes. Disabilityrates were 27–35% higher amongwomen with diabetes than men with di-abetes; sex-related differences in dis-ability were smaller among those withoutdiabetes.

Incidence of remission from disabilitywas .20% per year for most strata (Ta-ble 2), was greater for those without di-abetes than for those with diabetes, anddeclined substantially with age in allgroups (data not shown, P , 0.001).Mortality rates among those with dia-betes were about twice as high as theircounterparts without diabetes, but therelative risk of mortality associated withdiabetes decreased with increasing age(data not shown). Additional analysesadjusting for prevalent CVD at baselineresulted in a,0.3 percentage point dif-ference from the estimates unadjustedfor prevalent CVD (SupplementaryTable 1).

Disability-Free and DisabledLife-YearsAcross all ages and disability definitions,having diabetes was significantly asso-ciated with reduced years of total lifeand reduced disability-free life-yearscompared with people without diabe-tes (Tables 3 and 4). However, therewas a greater impact of diabetes on dis-ability-free life-years than on total life-years, and those with diabetes spent agreater proportion of their remainingyears in a disabled state, particularlyamong those incident at younger ages.This is illustrated in Fig. 2A and B formobility loss disability; results weresimilar for ADL and IADL disability(data not shown). From age 50, menwith diabetes died 4.6 years earlier, de-veloped disability 6 years earlier, andspent 1–1.5 more years in a disabledstate than men without diabetes. Thismeans that men with diabetes spentabout twice as much of their remainingyears disabled (20–24% of remaininglife across the three disability defini-tions) compared with men without di-abetes (12–16% of remaining life acrossthe three disability definitions). With

Figure 1—The five-state Markov model.

care.diabetesjournals.org Bardenheier and Associates 3

increasing baseline age, diabetes wasstill associated with significant reduc-tions in the number of total and disabil-ity-free life-years, but the absolutedifference in years lost between thosewith and without diabetes was less thanat younger baseline age; the exceptionsto this were that by ages 60, 70, and 80,

IADL disabled years were no longer sig-nificantly different between groups,and by ages 70 and 80, the differencein ADL disabled years between peoplewith and without diabetes was nolonger significant.

Similar associations between diabetesstatus and disability-free and disabled

years were observed among women.From age 50, women with diabeteshad an average disability onset 6–7years earlier than women without dia-betes and lived 1–2 years longer in adisabled state. The largest differencewas observed for mobility disability,where women with diabetes from age

Table 1—General characteristics of study population according to diabetes status at baseline

Men Women

Diabetes, n (%) No diabetes, n (%) n total deaths* Diabetes, n (%) No diabetes, n (%) n total deaths*

Age (years)50–59 318 (31.8) 2,225 (41.9) 515 371 (26.5) 3,036 (37.3) 48260–69 504 (31.9) 2,562 (28.0) 1,098 537 (30.8) 3,081 (26.6) 94470–79 390 (27.2) 1,803 (21.9) 1,490 428 (30.0) 2,293 (23.7) 1,55580+ 138 (9.1) 745 (8.2) 847 208 (12.7) 1,369 (12.3) 1,401

Mean age 6 SE 65.8 6 0.4 63.9 6 0.2 d 67.5 6 0.3 65.5 6 0.2 d

Race/ethnicityNon-Hispanic white 950 (79.0) 5,848 (86.6) 3,056 903 (70.3) 7,652 (85.6) 3,322Hispanic 137 (9.1) 509 (5.6) 273 188 (9.9) 650 (5.8) 274Non-Hispanic black 232 (11.9) 830 (7.8) 545 417 (19.8) 1,298 (8.6) 721

Education,HS 473 (30.2) 1,970 (22.7) 1,475 686 (40.7) 2,588 (23.5) 1,739HS 626 (48.0) 3,480 (48.5) 1,776 696 (47.5) 5,451 (56.9) 2,148.HS 251 (21.8) 1,885 (28.8) 699 162 (11.8) 1,740 (19.6) 495

BMI (kg/m2),25 308 (22.1) 2,407 (31.8) 1,517 373 (25.2) 4,395 (46.6) 2,09925 to ,30 585 (42.7) 3,485 (47.7) 1,718 496 (32.2) 3,197 (32.9) 1,298$30 455 (35.2) 1,427 (20.5) 708 641 (42.6) 1,993 (20.5) 900

Prevalent ADL 277 (20.6) 909 (11.1) 842 475 (29.0) 1,555 (14.9) 1,341

Prevalent IADL 245 (17.5) 779 (9.6) 770 417 (25.5) 1,326 (12.6) 1,262

Prevalent mobility loss 204 (15.2) 537 (6.4) 572 404 (25.5) 1,165 (11.2) 1,059

Cardiovascular diseaseHigh blood pressure 814 (59.7) 2,853 (36.9) 1,911 1,080 (68.4) 4,030 (38.6) 2,476Heart disease 485 (34.6) 1,618 (20.1) 1,405 485 (31.7) 1,512 (14.6) 1,312Stroke 168 (12.6) 471 (5.7) 494 181 (11.3) 546 (5.4) 547Arthritis 743 (53.3) 3,283 (41.4) 2,077 1,084 (69.0) 5,594 (54.6) 2,920Lung disease 105 (8.2) 549 (6.6) 505 140 (9.2) 623 (6.0) 523

Entered nursing home after baseline 24 (1.8) 92 (1.2) d 52 (3.2) 281 (2.9) d

All data are self-reported, except death, which is reported by proxy, friend, or family, and confirmed with the National Death Index. Dashes indicatecell size too small to report for confidentiality. HS, high school. *Died prior to end of the study.

Table 2—Incidence (annual % and 95% CI) of major sources of morbidity affecting disability-free life-years among U.S. menand women with and without diabetes

Men Women

Diabetes No diabetes Diabetes No diabetes

Disability incidenceSevere mobility loss 3.3** (3.0, 3.6) 1.7 (1.6, 1.8) 5.0** (4.6, 5.4) 2.6 (2.4, 2.7)IADL 3.5** (3.2, 3.8) 2.2 (2.1, 2.4) 4.9** (4.6, 5.3) 2.7 (2.5, 2.8)ADL 3.8** (3.5, 4.1) 2.3 (2.2, 2.4) 5.1** (4.8, 5.5) 2.9 (2.8, 3.0)

Mortality rate 4.1** (3.8, 4.4) 2.8 (2.7, 2.9) 4.0** (3.8, 4.3) 2.4 (2.3, 2.5)

Disability remission*Severe mobility loss 19.7** (17.6, 21.9) 23.4 (21.7, 25.1) 19.2 (17.3, 20.8) 20.9 (19.8, 22.0)IADL 22.1 (20.2, 24.0) 23.5 (22.3, 24.8) 16.7** (15.1, 18.2) 18.3 (17.0, 19.5)ADL 22.0** (20.3, 23.7) 25.3 (23.9, 26.6) 18.6** (17.3, 19.9) 22.4 (21.3, 23.5)

All models were adjusted for age, race/ethnicity, and sex. *Estimated among people with incident disability. **P value,0.001 between those withand without diabetes within sex.

4 Disability-Free Life-Years and Diabetes Diabetes Care

50 lost 7 disability-free years and had2.5 more disabled years comparedwith women without diabetes. Alsosimilar to men, women with diabetesspent about one and a half times asmuch of their remaining years disabled(27–32% across the three disability def-initions) as women without diabetes(20–22% across the three disability def-initions). Similar to men, the diabeticversus nondiabetic differences in dis-ability among women were significantand decreased with increasing age; theexceptions to this were that by ages 70and 80, differences in IADL disabled

years between all adults with and with-out diabetes were no longer significant,and by ages 70 and 80, the differencein ADL disabled years was no longersignificant.

CONCLUSIONS

Using a large, nationally representativecohort of Americans aged 50 years andolder, we found that diabetes is asso-ciated with a substantial deteriorationof nondisabled years, and this is agreater number of years than on theloss of longevity associated with diabe-tes. On average, a middle-aged adult

with diabetes has an onset of disability6–7 years earlier than one without dia-betes, spends 1–2 more years with dis-ability, and loses 7 years of disability-freelife to the condition. Although other na-tionally representative studies have re-ported large reductions in complications(9) and mortality among the populationwith diabetes in recent decades (1),these studies, akin to our results, suggestthat diabetes continues to have a sub-stantial impact on morbidity and qualityof remaining years of life.

The differences in disability-free anddisabled life-years between people with

Table 3—Number of disability-free and disabled years by disability type among U.S. men with and without diabetes

Diabetes No diabetes

Disabilitytype†

Disability onset(age)

Disability-freeyears (n)

Disabledyears (n)

Total years(n)

Disability onset(age)

Disability-freeyears (n)

Disabledyears (n)

Total years(n)

Mobility50 72.4* 22.4* 5.6* 28.0* 78.6 28.6 4.0 32.660 75.9* 15.9* 3.7* 19.6* 80.8 20.8 2.9 23.670 80.2* 10.2* 2.5* 12.8* 83.9 13.9 2.1 16.080 85.9* 5.9* 1.5* 7.4* 88.2 8.2 1.2 9.6

IADL50 72.2* 22.2* 5.8* 28.0* 77.5 27.5 5.0 32.660 75.7* 15.7* 3.9 19.6* 80.0 20.0 3.7 23.670 79.9* 9.9* 2.9 12.8* 83.1 13.1 2.9 16.080 85.4* 5.4* 2.0 7.4* 87.5 7.5 2.1 9.6

ADL50 71.4* 21.4* 6.6* 28.0* 77.3 27.3 5.3 32.660 75.4* 15.4* 4.2* 19.6* 80.0 19.7 3.7 23.670 79.8* 9.8* 3.0 12.8* 83.2 13.0 2.7 16.080 85.5* 5.5* 1.9 7.4* 87.7 7.5 1.9 9.6

*Indicates statistically significantly different between those with and without diabetes at P , 0.05. †From baseline age.

Table 4—Number of disability-free and disabled years by disability type among U.S. women with and without diabetes

Diabetes No diabetes

Disabilitytype†

Disability onset(age)

Disability-freeyears (n)

Disabledyears (n)

Total years(n)

Disability onset(age)

Disability-freeyears (n)

Disabledyears (n)

Total years(n)

Mobility50 71.6* 21.6* 9.6* 31.2* 78.6 28.6 7.1 35.760 75.8* 15.8* 6.7* 22.4* 81.2 21.2 5.3 26.570 80.4* 10.4* 4.6* 15.0* 84.5 14.5 3.9 18.380 86.1* 6.1* 2.8* 8.9* 88.7 8.7 2.5 11.2

IADL50 72.7* 22.7* 8.5* 31.2* 78.3 28.3 7.3 35.760 76.5* 16.5* 6.0* 22.4* 80.9 20.9 5.6 26.570 80.5* 10.5* 4.5 15.0* 83.9 13.9 4.4 18.380 85.8* 5.8* 3.0 8.9* 88.0 8.0 3.2 11.2

ADL50 71.3* 21.3* 9.9* 31.2* 77.6 27.6 8.0 35.760 75.8* 15.8* 6.6* 22.4* 80.7 20.7 5.8 26.570 80.3* 10.3* 4.7 15.0* 83.9 13.9 4.4 18.380 85.8* 5.8* 3.0 8.9* 88.2 8.2 3.0 11.2

*Indicates statistically significantly different between those with and without diabetes at P , 0.05. †From baseline age.

care.diabetesjournals.org Bardenheier and Associates 5

and without diabetes were driven byseveral factors. First, people with diabe-tes had considerably higher disability in-cidence at all ages, leading to a youngerage of disability onset and more yearsspent in a disabled state. Second, once aperson with diabetes became disabled,they were less likely to revert to regularfunctioning, therein increasing the num-ber of years with disability. Third, diabe-tes and disability were each associatedwith increased mortality, which has amodest contradictory effect on the firsttwo factors (i.e., incidence and remis-sion of disability), as the increased mor-tality reduces the number of years spentin both a healthy and unhealthy state.Given this combination of factors, im-proving the number of disability-freelife-years over time will depend uponidentification of interventions that can

reduce disability and increase remissionat least as much as mortality rates arebeing reduced.

The association of diabetes with dis-ability has been found to be multifac-torial (4,16,17). Previous studies havesuggested that coronary heart disease(CHD), lower extremity arterial dis-ease, and obesity explain a particularlylarge proportion of the difference indisability between people with andwithout diabetes (4,16,18). However,these factors are likely to vary by sex,and numerous other factors, includingphysical inactivity, inflammatory fac-tors, insulin resistance, and diabetes-related complications (suchasneuropathy,kidney disease, stroke, hyperglycemia,and hypoglycemia) may intervene. Ourfindings related to mortality are alsoconsistent with national estimates

that among older adults, diabetes isassociated with 60–70% increases inmortality rates and 4.6–5.7 years of re-duced life spans (1). We are not awareof previous estimates of the rate of re-mission from disability, and it is note-worthy that people with diabetes wereless likely to recover from disability,which could also be an indication thattheir levels of disability were some-what more severe (19). Several recentdevelopments in the epidemiology ofdiabetes complications from interven-tion studies have made disability-freeand disabled years increasingly impor-tant metrics for assessing the impact ofdiabetes. Although rates of complica-tions have declined, the extra years oflife spent with diabetes and cumulativemorbidity that follows could erode thequality of those extra years of life. Also,

Figure 2—A: Disability-free and mobility loss disability life-years remaining by age for men with and without diabetes. B: Disability-free and mobilityloss disability life-years remaining by age for women with and without diabetes. (A high-quality color representation of this figure is available in theonline issue.)

6 Disability-Free Life-Years and Diabetes Diabetes Care

older adults are the fastest growingsegment of the population with diabe-tes, raising the importance of physicaldisability and other geriatric syn-dromes that may result from or be as-sociated with diabetes (20).In addition, and perhaps most impor-

tantly, there is increasing evidence thatdisability is modifiable with lifestyle in-terventions (14,21). The Look AHEADStudy found that intensive lifestyle in-tervention results in a 50% reduced in-cidence of physical disability amongadults with diabetes (14). Similarly, thegeneral effectiveness of similar inter-ventions among older and overweightadults with osteoarthritis has foundthat structured exercise and moderateweight loss programs can improve func-tional status (22). In theory, many otheraspects of risk factor modification initi-ated through primary care, includingglycemic and blood pressure control,could also affect disability risk, but therehas been little evaluation of the effectsof such interventions on disability. Wedid not adjust for other risk factors formorbidity and mortality, such as hyper-tension, obesity, CHD, and stroke, whichwere largely unbalanced among peoplewith and without diabetes at baseline sothat we could determine the overalldifferences in remaining disability life-years and disability-free life-years be-tween those with and without diabetes.However, incidence of disability, re-mission from disability, and mortalitychanged only slightly when adjustingfor prevalent CVD. Assessing the contri-bution of the specific related reason forthe differences is warranted.There are several limitations to this

study. First, diabetes was based onself-report, which means that peoplewith undiagnosed diabetes were classi-fied as not having diabetes; if their dis-ability risk is higher than adults trulywithout diabetes, the difference in dis-ability-free life-years between adultswith and without diabetes in our analy-ses would be underestimated. Our dis-ability estimates are also based onsubjective reports, for which interpre-tation and agreement with objectivemeasurements could vary by diabetesstatus. Third, we could not distinguishbetween secondary diagnosis of diabe-tes and primary diagnosis due to theself-reporting of the diagnosis. Fourth,although the incident cases of diabetes

were accounted for in the age-specificprobabilities input into the Markovmodels, those models were designedto compare people with prevalent dia-betes and those without prevalent dia-betes who do not develop diabetes intheir lifetime. Thus, the final estimatesshould be interpreted with the assump-tion that diabetes status did not changeat the specified age. Although the ma-jority of people without diabetes atage 70 will not develop diabetes, thisignores a substantial minority of peoplewho become incident diabetes cases af-ter baseline. The group of people whogo on to develop diabetes later are likelyto have a number of disability-free andtotal years remaining that is intermedi-ate between the groups with and with-out diabetes. Finally, our estimates didnot adjust for potential intervening andconfounding factors such as obesity,CHD, and lower extremity disease. How-ever, the objective here was to quantifythe basic differences in disability-freelife-years by diabetes status occurringin the U.S. population.

Despite these limitations, theseanalyses are the first-ever quantifica-tion of disability-free and disabledyears experienced after age 50 for theU.S. population with diabetes, whichincorporates information on disabilityincidence, disability remission, andmortality across older ages. As such,these findings are an important base-line from which to monitor the successof future clinical and public health ef-forts to reduce diabetes and its compli-cations as well as interventions aimeddirectly at reducing disability.

Acknowledgments. The authors thank TonyPearson-Clarke, Centers for Disease Control andPrevention, for help with editing.Duality of Interest. X.Z. is currently working forMerck. No other potential conflicts of interestrelevant to this article were reported.Author Contributions. B.H.B. conducted thedata analysis, researched data, contributed todiscussion, and wrote, reviewed, and editedthemanuscript. J.L., X.Z., and E.W.G. researcheddata, contributed to discussion, and wrote,reviewed, and edited the manuscript. M.K.A.,T.J.T., and Y.J.C. researched data, contributed todiscussion, and reviewed and edited the manu-script. B.H.B. is the guarantor of thiswork and, assuch, had full access to all the data in the studyand takes responsibility for the integrity of thedata and the accuracy of the data analysis.PriorPresentation.This studywaspresented intwo oral guided posters at the 75th Scientific

Sessions of the American Diabetes Association,Boston, MA, 5–9 June 2015.

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