Impact Of Obesity And Physical Inactivity On The Long-term Change In Grip Strength Among Middle-aged And Older Adults

Aim:With the continuous declination of toal fertility rate and increasing life expectancy in the world,the aging of the population has become a problem faced by many countries and governments.As representative index of muscle strength,grip strength is a well-established predictor of various chronic conditions and all-cause mortality.Consequently,it is important in public health to understand the determinants for age-related decline of grip strength.Previous studies on the associations of obesity and physical activity with grip strength among middle-aged and older population were limited and the conclusions were inconsistent,especially the lack of evidence for longitudinal studies.Here,we conducted a prospective study using a large,population-based sample to investigate gender-specific associations of baseline obesity and physical inactivity with long-term changes in grip strength among middle-aged and older adults,providing scientific and effective intervention strategies for active and healthy ageing.Methods:Data from the Survey of Health,Ageing and Retirement in Europe?2004-2015?.SHARE have drawed representative samples from 27 European countries and Israel,using a multi-stage sampling method.Up to now,SHARE has collected five panel waves with average two-year intervals and a retrospective life history wave.The data for this study were from the five panel waves.This study yielded a total of 18,704 participants?n=8,616,46.1%for men and n=10,088,53.9%for women?in this study.In SHARE,the grip strength was measured using a handheld dynamometer?Smedley?.Body mass index?BMI?was calculated using self-reported height and weight.The baseline BMI was categorized as non-obesity?18.5?BMI<30 kg/m²?and obesity?BMI?30kg/m²?based on WHO classification criteria.Physical activity was obtained through questionnaire survey and divided into two levels according to the intensity and frequency of physical activity,namely,‘high physical activity'and‘low physical activity'.Obesity and physical inactivity at baseline were primary exposures.Generalized estimated equations?GEE?with five visits of grip strength as outcomes was fitted to identify the independent effects of exposures on the change of grip strength overtime.Based on combined exposure to obesity and physical activity,we grouped participants for all possible combinations,including non-obesity and physically active,obesity and physically active,non-obesity and physical inactivity as well as obesity and physical inactivity.GEE was carried out to explore the effect of the combined exposures on longitudinal change of grip strength.All of the GEE models were fitted by gender and were adjusted for the potential confounders:age,country,educational level,cigarette smoking,alcohol drinking,as well as history of depression,heart attack,arthritis,hypertension,hypercholesterolemia and diabetes at baseline.In addition,the main exposures of obesity and physical inactivity were adjusted mutually in the separate analysis.Results:During the median follow-up time of this cohort study was 9.42 years.At baseline,the mean grip strength of male and female were 44.13±10.51kg and 26.81±7.16kg,respectively.At the fifth panel survey,the grip strength were 40.53±9.62kg and24.43±6.41kg,respectively.The grip strength levels showed a continuous downward trend.At baseline,the prevalence of obesity was 16.7%in men and 18.3%in women and the prevalence of physical inactivity was 35.9%and 44.8%,respectively.The GEE results show that significant interactions between obesity and time with grip strength were identified in both males(?²_interaction=16.65,P=0.002)and females(?²_interaction=10.80,P=0.029).Compared with non-obese people,obese people had stronger grip strength at baseline?male:?=1.07,95%CI:0.54,1.60;female:?=0.64,95%CI:0.29,0.98?,but from the third panel survey,there was no significant difference in male grip strength between the two groups??=0.04,95%CI:-0.62,0.71?;from the fourth panel survey,there was no significant difference in female grip strength between the two groups??=0.22,95%CI:-0.21,0.64?.The results suggested that the grip strength of obese people decreases faster.No significant interaction between physical inactivity and time with grip strength was identified in males(?²_interaction=9.42,P=0.051)or females(?²_interaction=5.62,P=0.230).Compared with the low physical activity group,the high physical activity group have maintained a higher grip level during the follow-up period.There was significant difference between the two groups in the baseline survey?male:?=2.75,95%CI:2.33,3.18;female:?=1.53,95%CI:1.26,1.80?.At the end of the fifth panel survey,there was still significant difference between the two groups?male:?=2.79,95%CI:2.24,3.35;female:?=1.55,95%CI:1.21,1.89?.Further combined analysis suggested a trend that exposure to both obesity and physical inactivity was related to the fastest decline rate of grip strength.Conclusions:Although the individuals with higher baseline BMI had greater grip strength,obesity status at baseline predicted the faster decline of grip strength with ageing.No independently protective effect of high baseline PA on longitudinal decline of grip strength over time was found,however,those who were physically active at baseline had stronger grip strength during the whole follow-up years.The combination of obesity and physical inactivity might accelerate the decline of grip strength.In addition,this study did not find significant gender differences.This study provides the additional evidence that physical activity and obesity prevention earlier in life play an important role in maintaining grip strength during ageing.