| Background and ObjectivesPhysical function and cognitive function are vital to ensure a high quality of life among middle-aged and older adults.Grip strength is generally regarded as a major biomarker of physical function and is closely related to cognitive function.Therefore,this study mainly focuses on the relationship between grip strength and cognitive function changes,including the association of grip strength with mild cognitive impairment(MCI)incidence and cognitive decline,and further explores a doseresponse relationship,as well as whether there is vary in different age and sex strata.Study design and methodsOur study selected data from the Survey of Health,Aging,and Retirement in Europe(SHARE)database.This was a prospective cohort study that examined the health,socio-economic status and socio-family networks of people over the age of 50 living in Europe and Israel.Grip strength was measured by using hand dynamometer,taking the maximum value.Cognitive function included three aspects: immediate recall,delayed recall and verbal fluency.Global cognition was created by using the average of the three z-scores for immediate recall,delayed recall and verbal fluency.MCI was defined as 1.5 standard deviations below global cognition.In the first part,20750 cognitively normal subjects were followed up for an average of 8 years,using Cox proportional risk model to analyze the association of grip strength with MCI incidence,and whether a dose-response relationship between levels of grip strength and MCI incidence.In the second part,21114 people without dementia were followed for an average of 9 y,employing linear mixed model to explore the effect of grip strength on rate of cognitive decline.All the above conducted stratified analysis by age(50-65 vs65+)and sex.Results1.The relationship between baseline grip strength and incidence of MCIDuring a 11-year follow-up,1280(6.17%)participants developed MCI.The population was divided into three groups based on the level of grip strength.Compared with medium grip strength,weak grip strength was associated with a significantly increased risk of MCI in total population(HR = 1.63,95%CI: 1.43-1.86)after adjusting for age,sex,country,living arrangement and education,while the risk was reduced in people with strong grip strength(HR = 0.70,95%CI: 0.61-0.81).When broken down by age,the increased risk in people with weak grip strength was elevated in those over65 years(HR = 1.90,95%CI: 1.55-2.33)and reduced in those under 65 years(HR =1.51,95%CI: 1.26-1.81).A similar phenomenon occurred in people with weak grip strength when stratified by sex,with a significant increase for men(HR = 1.92,95%CI:1.58-2.34)but a decrease for women(HR = 1.40,95%CI: 1.17-1.68).In contrast,strong grip strength significantly reduced the risk of MCI incidence,with a significant increase for women(HR = 0.66,95%CI: 0.54-0.81)but a decrease for men(HR = 0.75,95%CI:0.61-0.92).In addition,there was a dose-response relationship between grip strength and the risk of MCI(P-trend < 0.001),i.e.,the weaker the grip strength,the higher the risk of MCI.After further adjusting for smoking,alcohol consumption,BMI,physical activity,number of chronic diseases and depression,the degree of higher risk of MCI decreased in the weak grip strength group,while the degree of lower risk of MCI remained in the strong grip strength group.2.The effect of baseline grip strength on rate of cognitive declineImmediate recall and global cognition decline in the medium and low grip strength group were significantly greater than that in the high grip strength(β =-0.005 and-0.005,P < 0.05;β =-0.004 and-0.005,P < 0.01)after adjusting for all relevant confounders.The rate of decline in delayed recall was faster only in people with medium grip strength(β =-0.005,P < 0.01),and the decline in verbal fluency was accelerated only for people with weak grip strength(β =-0.006,P < 0.01).For participants aged 50-65 y,the rates of decline in verbal fluency and global cognition were faster for people with weak grip strength,whereas only the decline in verbal fluency was accelerated in people over 65 years.Weaker baseline grip strength was associated with faster rate of decline in all cognitive modules in women,but not in men.ConclusionsWeak grip strength is related to increased risk of MCI,especially among people65+ years and men.Further,a dose-response relationship was observed between levels of grip strength and risk of MCI.In addition,medium and low grip strength were associated with the rate of cognitive decline,particularly in women.It is suggested that the decline of grip strength may have a predictive effect on the occurrence of cognitive impairment in people,which provides a new idea for the development of prevention and early detection of cognitive impairment measures. |
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