association of grip strength with dementia in a korean older population

RESEARCH ARTICLE

Association of grip strength with dementia in a Koreanolder population

Hee‐Young Shin1,2, Sung‐Wan Kim3, Jae‐Min Kim3, Il‐Seon Shin3 and Jin‐Sang Yoon2,3

1Department of Biomedical Science, Chonnam National University Medical School, Gwangju, Korea2Clinical Trial Center, Chonnam National University Hospital, Gwangju, Korea3Department of Psychiatry, Chonnam National University Medical School, Gwangju, KoreaCorrespondence to: I.‐S. Shin, E‐mail: [email protected]

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Background: Several studies have found that low grip strength is associated with dementia in Westernpopulations. However, there have been few studies in Asian populations. This cross‐sectional studyaimed to examine whether grip strength is independently associated with dementia after controlling forother related factors in a Korean older population.Methods:One thousand thirty‐eight community‐dwelling older people aged 65 or over within a definedgeographic area were screened for dementia. Data on grip strength, sit‐to‐stand score, body mass index(BMI), socio‐demographic factors (age, gender, marital status, education), and medical conditions(diabetes, hypertension, heart disease, stroke) were collected. Dementia was diagnosed with the 10/66dementia diagnostic algorithm.Results: Eleven percent of the participants were found to have dementia. After adjustment for otherfactors, grip strength (per 8‐kg decrease) was independently associated with dementia (odds ratio, 1.59;95% confidence interval, 1.19–2.14). Adjusted grip strength by BMI interaction terms showed marginalsignificance (p= 0.098); that is, older people with both reduced grip strength and low BMI were likelyto be at higher risk for dementia.Conclusions: Reduced grip strength was independently associated with dementia in a Korean olderpopulation. This association was partially influenced by BMI. Copyright© 2011 JohnWiley & Sons, Ltd.

Key words: grip strength; dementia; aged; body mass index; KoreaHistory: Received 20 December 2010; Accepted 5 April 2011; Published online 27 May 2011 in Wiley Online Library(wileyonlinelibrary.com).DOI: 10.1002/gps.2742

Introduction

Dementia is characterized by a progressive loss ofmemory and other cognitive abilities. However,persons with dementia may also show non‐cognitivefeatures such as impaired motor function (Goldmanet al., 1999; Scarmeas et al., 2005). The nature of theassociation between motor function and cognitiveperformance is still uncertain, but because bothmuscle strength and cognitive performance involvethe central nervous system, shared age‐related pro-cesses have been suggested (Salthouse et al., 1998;Christensen et al., 2001).

Loss of grip strength is a well‐recognized feature ofage‐relatedmotor decline. Although several studies havefound that low grip strength is associated with dementia

ight © 2011 John Wiley & Sons, Ltd.

in Western populations, few studies have been carriedout in Asian populations (Alfaro‐Acha et al., 2006;Buchman et al., 2007). The sit‐to‐stand test may beconsidered as a rough measure for motor function oflower extremities, and sit‐to‐stand score has not beencompared to grip strength in previous studies. Further-more, some studies reported that body mass index(BMI) is related to dementia (Grundman, 2005;Buchman et al., 2005). As common age‐related condi-tions include reduced motor strength and changes inbody composition, BMI may affect the association ofgrip strength with dementia. Although BMI has beenadded as a covariate in a previous study investigating theassociation of grip strength with dementia for control-ling potential confounders, a possible interaction ofBMI was not considered (Buchman et al., 2007).

Int J Geriatr Psychiatry 2012; 27: 500–505.

501Grip strength and dementia

The purpose of this cross‐sectional study was toexamine whether grip strength is associated withdementia in a Korean older population and toinvestigate whether the association is modified byother factors such as BMI.

Methods

Study participants

The population for this study was community‐dwelling older people aged 65 or over within adefined geographic area of Kwangju, South Korea in2006. All community residents were systematicallyidentified from the national registration lists, andparticipants were recruited through a communitysurvey. Several community surveys of older peoplehave been carried out in Kwangju from 2001 and 2006in collaboration with the 10/66 Dementia in Devel-oping Countries Research Program (Prince et al.,2003). Informed consent was obtained from allparticipants or their family members, and the studywas approved by the Chonnam National UniversityHospital Institutional Review Board.

Of 2201 residents aged 65 or over identified fromthe national registration lists, 1038 (47%) completedthe interview. Of the remaining 1163, contact couldnot be established with 726 (33%), 330 (15%) refusedto participate (invitation declined by older residentsor their family members), 90 (4%) had no fixedabode, and 17 (1%) had died before the visit. Nosignificant differences were observed in age (mean age,73.4 and 73.2 years, respectively) and gender ratio(65% and 63% female, respectively) between partici-pants and non‐participants (all p‐values >0.05).

Assessments and measurements

Before the survey, a letter explaining the study wassent to all potential participants. Research nurses weretrained and supervised by the project psychiatrist, andthey carried out a home‐based interview for allparticipants. Socio‐demographic information on age,gender, marital status, and education was collectedfrom participants and family members. Self‐reporteddiagnoses and treatment histories for hypertension,diabetes, heart disease, and stroke were recorded.

Weight and height were measured, and BMI wascalculated as weight in kilograms divided by height inmeters squared. Grip strength was measured for bothhands in kilograms with a handheld dynamometer(T.K.K. 5401, Grip D, Takei Scientific Instruments

Copyright © 2011 John Wiley & Sons, Ltd.

Co., Niigata, Japan). The test was administered by atrained interviewer. Measures for both hands wereaveraged to yield a composite measure of grip strength.Participants were asked to do a sit‐to‐stand test andwere scored on a three‐point scale: 1, cannot stand orstand with other’s help; 2, stand with support of hands;3, stand without support.

Ascertainment of dementia

The participants completed the Korean version ofGeriatric Mental State Schedule B3 (GMS B3‐K)(Copeland et al., 1986), Community Screening Inter-view for Dementia (CSID‐K) (Kim et al., 2004), andmodified 10‐word list learning from the Consortium toEstablish a Registry of Alzheimer’s Disease (CERAD).Dementia diagnosis was made with the 10/66 dementiadiagnostic algorithm using the results derived from theabove three measures (Prince et al., 2003).

Statistical analysis

T‐test and χ2 test were used to examine thedistribution of covariates for subjects by dementiastatus. Spearman correlation was used to examine theassociation between grip strength and sit‐to‐standscore. The prevalence of dementia with 95% confi-dence intervals (95% CIs) was presented by gripstrength quintiles and sit‐to‐stand score, and a trendtest was performed. Logistic regression models wereused to adjust for other covariates. Grip strength wasentered as a continuous variable, and 8 kg or thestandard deviation was selected for the unit of change.After significant factors associated with dementia werefound in the univariate analysis, gender, age, educa-tion, marital status, and BMI were entered ascovariates in the models. Additionally, medicalhistories for hypertension, diabetes, heart disease,and stroke were entered as covariates for controllingpotential confounders. Because of gender and BMIdifferences in grip strength/sit‐to‐stand score, regres-sion models were stratified and interaction termstested. PASW statistics 18 software was used for theanalysis.

Results

Prevalence and associations of dementia

One hundred fourteen (11.0%) of the participantswere found to have dementia. Age, gender, marital


502 H.‐Y. Shin et al.

status, education, BMI, grip strength, and sit‐to‐standscore were identified as associated factors of dementiaby t‐test or χ 2 test (Table 1). However, dementia wasnot associated with diabetes, hypertension, heartdisease, or stroke reported at the time of interview.Grip strength was correlated with sit‐to‐stand score(ρ= 0.402; p< 0.001).

Prevalence rates of dementia by gripstrength/sit‐to‐stand score

The prevalence rates of dementia for each quintile ofgrip strength (lowest to highest) were 27.5%, 12.0%,7.2%, 5.3%, and 1.9% (χ2 = 70.8; p< 0.001) (Figure 1).Older people with lower grip strength had higher

Table 1 Characteristics of study participants by dementia status

Characteristics No dementia (n=924; 89%

Age (years), mean (SD) 72.8 (6.5)Gender (female), n (%) 579 (62.7)Education (years), mean (SD) 5.0 (4.4)Marital status (married), n (%) 520 (56.3)BMI (kg/m2), mean (SD) 23.8 (3.3)Grip strength (kg), mean (SD)Women 16.6 (5.5)Men 29.2 (7.1)

Sit‐to‐stand score, mean (SD)Women 2.3 (0.6)Men 2.6 (0.6)

Diabetes, n (%) 133 (14.4)Hypertension, n (%) 397 (43.0)Heart disease, n (%) 158 (17.1)Stroke, n (%) 47 (5.1)

Data were analyzed by t‐test or χ2 test as appropriate.

Figure 1 Prevalence rates of dementia by grip strength quintiles and sit‐to‐squintile.


prevalence of dementia. The prevalence rates ofdementia for sit‐to‐stand score (lowest to highest)were 34.4%, 14.9%, and 3.7% (χ 2 = 48.4, p< 0.001).

Grip strength/sit‐to‐stand score and dementia—logisticregression models

The results of the regression and stratified analyses aresummarized in Tables 2 and 3. The unadjusted oddsratios (OR) for dementia were 2.75 (95% CI, 2.14–3.54) for each standard deviation (8 kg) decrease ingrip strength and 2.87 (95% CI, 2.06–4.02) for 1‐pointdecrease in sit‐to‐stand score. After adjustment for age,education, marital status, BMI, diabetes, hyperten-sion, heart disease, and stroke, grip strength (per 8‐kg

) Dementia (n=114; 11%) p‐value

78.1 (7.6) <0.00197 (85.1) <0.0011.4 (3.0) <0.00124 (21.1) <0.001

22.9 (3.3) 0.008

12.2 (5.8) <0.00123.9 (10.6) 0.063

2.0 (0.5) <0.0012.1 (0.7) <0.00118 (15.8) 0.69450 (43.9) 0.86314 (12.3) 0.1929 (7.9) 0.212

tand score. 1st, lowest grip strength quintile; 5th, highest grip strength


Table 2 Logistic regression models stratified by gender for the association between grip strength/sit‐to‐stand score and dementia

Models Grip strength (per 8‐kg decrease),n=1038

Sit‐to‐stand score (per 1‐point decrease),n=1038

Unadjusted 2.75 (2.14–3.54) 3.89 (2.60–5.82)(1) Adjusted for gender 2.87 (2.16–3.84) 3.56 (2.34–5.40)(2) Model 1 plus age 2.14 (1.56–2.95) 2.37 (1.50–3.74)(3) Model 2 plus education 1.92 (1.40–2.66) 2.07 (1.30–3.31)(4) Model 3 plus marital status 1.91 (1.38–2.66) 2.04 (1.27–3.28)(5) Model 4 plus BMI 1.80 (1.28–2.51) 2.29 (1.37–3.83)(6) Model 5 plus diabetes, hypertension,

heart disease, stroke1.76 (1.25–2.48) 2.28 (1.35–3.86)

Data are presented as ORs with 95% CIs.

Table 3 Logistic regression models stratified by BMI for the association between grip strength/sit‐to‐stand score and dementia

Models Grip strength (per 8‐kg decrease) Sit‐to‐stand score (per 1‐point decrease)

BMI < 20(n=130)

20≤BMI<25(n=543)

BMI≥25(n=343)

BMI< 20(n=130)

20≤BMI<25(n=543)

BMI≥ 25(n=343)

Unadjusted 5.70 (2.51–12.93) 2.42 (1.76–3.32) 1.88 (1.15–3.06) 7.03 (2.24–22.04) 4.24 (2.34–7.69) 3.39 (1.40–8.24)(1) Adjusted for

gender3.78 (1.52–9.44) 2.66 (1.80–3.97) 2.21 (1.26–3.86) 14.73 (1.91–113.49) 3.74 (2.04–6.89) 3.32 (1.34–8.22)

(2) Model 1 plusage

2.44 (0.90–6.60) 2.05 (1.33–3.15) 1.93 (1.07–3.51) 10.55 (1.22–91.59) 2.60 (1.35–5.01) 2.68 (1.03–6.98)

(3) Model 2 pluseducation

2.34 (0.82–6.60) 1.99 (1.29–3.10) 1.53 (0.84–2.81) 11.16 (1.18–104.79) 2.28 (1.17–4.47) 2.44 (0.87–6.80)

(4) Model 3 plusmarital status

2.42 (0.84–7.07) 1.89 (1.21–2.97) 1.55 (0.84–2.83) 10.83 (1.14–102.68) 2.22 (1.12–4.38) 2.53 (0.89–7.20)

(5) Model 4 plusdiabetes,hypertension,heart disease,stroke

2.22 (0.72–6.98) 1.84 (1.16–2.89) 1.49 (0.80–2.77) 11.75 (0.95–145.66) 2.16 (1.09–4.28) 2.62 (0.91–7.56)

Data are presented as ORs with 95% CIs.Test for grip strength by BMI interaction terms: p = 0.098; test for sit‐to‐stand score by BMI interaction terms: p = 0.622.


decrease) and sit‐to‐stand score (per 1‐point decrease)were independently associated with dementia (ORs,1.59 (95% CI, 1.19–2.14) and 2.11 (95% CI, 1.30–3.43), respectively). Adjusted grip strength by genderterms showed no statistical significance (p= 0.511),whereas adjusted grip strength by BMI interactionterms showed marginal significance (p= 0.098). Olderpeople with low BMI and reduced grip strength werelikely to be at higher risk for dementia. P‐values foradjusted sit‐to‐stand score by gender and sit‐to‐standscore by BMI interaction terms were 0.549 and 0.622for dementia, respectively.

Discussion

In this cross‐sectional study of a community‐dwellingKorean older population, reduced grip strength and


low sit‐to‐stand score were independently associatedwith dementia after controlling for other factors.There were no significant gender differences in theassociations between grip strength/sit‐to‐stand scoreand dementia. However, whereas the associationbetween grip strength and dementia was influencedby BMI, the association between sit‐to‐stand score anddementia was not.

Our findings are similar to the results from previousstudies suggesting an association between reduced gripstrength and cognitive decline (Christensen et al., 1999;MacDonald et al., 2004; Alfaro‐Acha et al., 2006). Anumber of studies have reported that low grip strengthis related to dementia in Western populations, butthere are few published studies on Asian populations(Anstey and Smith, 1999; Buchman et al., 2007).Furthermore, the relationship between grip strengthand dementia across different ethnic groups has


504 H.‐Y. Shin et al.

received little research attention. A previous studyfound that muscle strength differs in disabled olderwomen by race (Rantanen et al., 1998). In otherstudies, some factors predicting cognitive decline inHispanic older persons seemed to be different fromthose factors in non‐Hispanic older persons (Hohlet al., 1999; Mulgrew et al., 1999). More studies need tobe conducted on the role of ethnicity in the associationof grip strength with dementia.

In our study, adjusted grip strength by BMIinteraction terms for dementia were statisticallysignificant. That is, older people with low BMI andreduced grip strength were at higher risk fordementia. BMI is a commonly used measure of bodycomposition that has been associated with mortalityand a wide variety of medical diseases (Stevens et al.,1998). Furthermore, some studies report that BMI isrelated to dementia and can affect muscle strength(Grundman, 2005; Buchman et al., 2005; Buchmanet al., 2006).

A recent meta‐analysis study showed evidence ofassociation between grip strength, a simple objectivemeasure of physical capability, and mortality (Cooper,2010). Grip strength measured at younger agespredicted mortality; however, the association of othermeasures such as walking speed, chair rise time, andstanding balance performance with mortality inyounger populations was not clear. Considering theassociation between grip strength and dementia ormortality, lower grip strength may be an easy way toidentify persons most likely to benefit from exerciseprograms that improve muscle strength.

Several mechanisms have been suggested for therelationship between grip strength and cognition. Oneof the proposed explanations was shared age‐relatedprocesses, which suggests that non‐cognitive variablessuch as muscle strength are shared with cognitivevariables because they both involve the centralnervous system (Salthouse et al., 1998). Measures ofmuscle strength may be viewed as a marker of theintegrity of the central nervous system (Salthouseet al., 1998). Another possible explanation for theassociation between low grip strength and poorcognitive functioning is the presence of a commonpathogenic inflammatory mechanism. One studyreported a significant association between high levelof inflammatory marker (interleukin‐6) and cognitivedecline (Weaver et al., 2002), and another studyshowed a relationship between elevated levels ofinflammatory markers and low grip strength (Cesariet al., 2004). Frailty also needs to be considered for theassociation between reduced grip strength and demen-tia. Frailty is common in older people, and it is


characterized by multi‐system impairments such asvulnerability to stressors, decreased strength, andincreased risk of morbidity, disability, and mortality(Fried et al., 2001). One study reports on the associationbetween frailty and the pathology of Alzheimer’sdisease (Buchman et al., 2008). Another possibleexplanation concerns physical reserve in dementiadiagnosis. People with a given level of cognitiveimpairment are more likely to have functionalimpairment if they also have physical impairment suchas reduced muscle strength (Kim et al., 2010).

This study has some limitations. Because the studywas a population‐based cross‐sectional survey, thetemporal relationship between exposure and onset ofdisease often cannot be established. There is also thepossibility of reverse causality: people with dementiamay have poorer diets and reduced physical activity,which result in low grip strength. In addition, peoplewith dementia may not understand the task used formeasuring grip strength, and it might affect gripstrength. A prospective study needs to be carried outto confirm the association. Concerning dementia diag-nosis, neuroimaging data could not be obtained. How-ever, this is the first report on the association betweenreduced grip strength and dementia in a Korean olderpopulation. The sample was representative of thesource population using the national registrationlists, which are a highly inclusive sampling framein Korea. Dementia diagnosis was made accordingto the culturally and educationally sensitive 10/66dementia diagnostic algorithm, which had been val-idated (Prince et al., 2003). Compared with the 10/66dementia algorithm, the DSM‐IV dementia criteriamight substantially underestimate the true prevalenceof dementia in less developed regions because ofdifficulties in defining and ascertaining the decline inintellectual function and its consequences (Rodriguezet al., 2008). In our study, the prevalence of dementiawas 11.0% by the 10/66 dementia diagnostic algo-rithm, and it was similar to the results of other studiesin Korea (Shin et al., 2005; Cho et al., 1998).

In conclusion, low grip strength was found to beindependently associated with dementia in a Koreancommunity‐dwelling older population. Older peoplewith low BMI and reduced grip strength were likely tobe at higher risk for dementia. Therefore, this groupof older adults should be given more focus in terms ofexercise programs.

Conflict of interest

None declared.


Key points

• Reduced grip strength was independently asso-ciated with dementia in a Korean olderpopulation.

• In particular, older people with low BMI andreduced grip strength were likely to be at higher


risk for dementia.

Acknowledgements

This study was funded by a grant from the KoreaHealth 21 R&D Project, Ministry of Health andWelfare, Republic of Korea (A050174).

References

Alfaro‐Acha A, Al Snih S, Raji MA, et al. 2006. Handgrip strength and cognitivedecline in older Mexican Americans. J Gerontol A Biol Sci Med Sci 61: 859–865.

Anstey KJ, Smith GA. 1999. Interrelationship among biological markers of aging,health, activity, acculturation, and cognitive performance in late adulthood.Psychol Aging 14: 605–618.

Buchman AS, Schneider JA, Leurgans S, et al. 2008. Physical frailty in older persons isassociated with Alzheimer’s disease pathology. Neurology 71: 499–504.

Buchman AS, Schneider JA, Wilson RS, et al. 2006. Body mass index in older personsis associated with Alzheimer disease pathology. Neurology 67: 1949–1954.

Buchman AS, Wilson RS, Bienias JL, et al. 2005. Change in body mass index and riskof incident Alzheimer disease. Neurology 65: 892–897.

Buchman AS, Wilson RS, Boyle PA, et al. 2007. Grip strength and the risk of incidentAlzheimer’s disease. Arch Intern Med 29: 66–73.

Cesari M, Penninx BW, Pahor M, et al. 2004. Inflammatory markers and physicalperformance in older persons: the InCHIANTI study. J Gerontol A Biol Sci Med Sci59: 242–248.

Cho MJ, Hahm BJ, Ju JH, et al. 1998. The prevalence of cognitive impairment anddementia among the elderly in a city. J Korean Neuropsychiatr Assoc 37: 352–362.

Christensen H, Mackinnon AJ, Korten AE, et al. 1999. An analysis of diversity in thecognitive performance of elderly community dwellers: individual differences inchange scores as a functional age. Psychol Aging 14: 365–379.


Christensen H, Mackinnon AJ, Korten AE, et al. 2001. The “common causehypothesis” of cognitive aging: evidence for not only a common factor but alsospecific associations of age with vision and grip strength in a cross‐sectionalanalysis. Psychol Aging 16: 588–599.

Cooper R. 2010. Objectively measured physical capability levels and mortality:systematic review and meta‐analysis. BMJ 341: c4467.

Copeland JRM, Dewey ME, Griffiths‐Jones HM. 1986. A computerized psychiatricdiagnostic system and case nomenclature for elderly subjects: GMS and AGECAT.Psychol Med 1986: 89–99.

Fried LP, Tangen CM, Walston J, et al. 2001. Frailty in older adults: evidence for aphenotype. J Gerontol A Biol Sci Med Sci 56: M146–M156.

Goldman WP, Baty JD, Buckles VD, et al. 1999. Motor dysfunction inmildly demented AD individuals without extrapyramidal signs. Neurology 53:956–962.

Grundman M. 2005. Weight loss in the elderly may be a sign of impending dementia.Arch Neurol 62: 20–22.

Hohl U, Grundman M, Salmon D, et al. 1999. Mini‐Mental State Examination MattisDementia Rating Scale performance differs in Hispanic and non‐HispanicAlzheimer’s disease patients. J Int Neuropsychol Soc 5: 301–307.

Kim JM, Kim SW, Shin IS, et al. 2004. Development of Korean version of Com-munity Screening Interview for Dementia (CSID‐K). J Korean NeuropsychiatrAssoc 43: 445–451.

Kim JM, Stewart R, Bae KY, et al. 2010. Role of BDNF val66met polymorphism onthe association between physical activity and incident dementia. Neurobiol Aging.doi:10.1016/j.neurobiolaging.2010.01.018

MacDonald SW, Dixon RA, Cohen AL, et al. 2004. Biological age and 12‐yearcognitive change in older adults: findings from the Victoria Longitudinal Study.Gerontology 50: 64–81.

Mulgrew C, Morgensten N, Shetterly S, et al. 1999. Cognitive functioning andimpairment among rural elderly Hispanic and non‐Hispanic Whites as assessedby the Mini‐Mental State Examination. J Gerontol Psychol Sci 54: P223–P230.

Prince M, Acosta D, Chiu H, et al. 2003. Dementia diagnosis in developing countries:a cross‐cultural validation study. Lancet 361: 909–917.

Rantanen T, Guralnik JM, Leveile S, et al. 1998. Racial differences in muscle strengthin disabled older women. J Gerontol Biol Sci 53: B355–B361.

Rodriguez JL, Ferri CP, Acosta D, et al. 2008. Prevalence of dementia in LatinAmerica, India, and China: a population‐based cross‐sectional survey. Lancet372: 464–474.

Salthouse TA, Hambrick DZ, McGuthry KE. 1998. Shared age‐related influences oncognitive and noncognitive variables. Psychol Aging 13: 486–500.

Scarmeas N, Albert M, Brandt J, et al. 2005. Motor signs predict poor outcomes inAlzheimer disease. Neurology 64: 1696–1703.

Shin HY, Chung EK, Rhee JA, et al. 2005. Prevalence and related factors of dementiain an urban elderly population using a new screening method. J Prev Med PublicHealth 38: 351–358.

Stevens J, Cai J, Pamuk ER, et al. 1998. The effect of age on the association betweenbody mass index and mortality. N Engl J Med 338: 1–7.

Weaver JD, Huang MH, Albert M, et al. 2002. Interleukin‐6 and risk of cognitivedecline: Mac Arthur Studies of Successful Aging. Neurology 59: 371–378.


association of grip strength with dementia in a korean older population

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