Richard Dodds

Grip Strength across the Life Course: Normative Data from Twelve British Studies

Introduction Epidemiological studies have shown that weaker grip strength in later life is associated with disability, morbidity, and mortality. Grip strength is a key component of the sarcopenia and frailty phenotypes and yet it is unclear how individual measurements should be interpreted. Our objective was to produce cross-sectional centile values for grip strength across the life course. A secondary objective was to examine the impact of different aspects of measurement protocol. Methods We combined 60,803 observations from 49,964 participants (26,687 female) of 12 general population studies in Great Britain. We produced centile curves for ages 4 to 90 and investigated the prevalence of weak grip, defined as strength at least 2.5 SDs below the gender-specific peak mean. We carried out a series of sensitivity analyses to assess the impact of dynamometer type and measurement position (seated or standing). Results Our results suggested three overall periods: an increase to peak in early adult life, maintenance through to midlife, and decline from midlife onwards. Males were on average stronger than females from adolescence onwards: males’ peak median grip was 51 kg between ages 29 and 39, compared to 31 kg in females between ages 26 and 42. Weak grip strength, defined as strength at least 2.5 SDs below the gender-specific peak mean, increased sharply with age, reaching a prevalence of 23% in males and 27% in females by age 80. Sensitivity analyses suggested our findings were robust to differences in dynamometer type and measurement position. Conclusion This is the first study to provide normative data for grip strength across the life course. These centile values have the potential to inform the clinical assessment of grip strength which is recognised as an important part of the identification of people with sarcopenia and frailty.

Birth weight and muscle strength: a systematic review and meta-analysis.

ObjectiveLower muscle strength is associated with a range of adverse health outcomes in later life. The variation in muscle strength between individuals is only partly accounted for by factors in adult life such as body size and physical activity. The aim of this review was to assess the strength of the association between intrauterine development (indicated by birth weight) and subsequent muscle strength.DesignSystematic review and meta-analysis of studies that assessed the association between birth weight and subsequent muscle strength.ResultsNineteen studies met inclusion criteria with 17 studies showing that higher birth weight was associated with greater muscle strength. Grip strength was used as a single measure of muscle strength in 15 studies. Metaanalysis (13 studies, 20 481 participants, mean ages 9.3 to 67.5) showed a 0.86 kg (95% CI 0.58, 1.15) increase in muscle strength per additional kilogram of birth weight, after adjustment for age, gender and height at the time of strength measurement.ConclusionThis review has found consistent evidence of a positive association between birth weight and muscle strength which is maintained across the lifecourse. Future work will be needed to elucidate the biological mechanisms underlying this association, but it suggests the potential benefit of an early intervention to help people maintain muscle strength in later life.

Global variation in grip strength: a systematic review and meta-analysis of normative data

Background: weak grip strength is a key component of sarcopenia and is associated with subsequent disability and mortality. We have recently established life course normative data for grip strength in Great Britain, but it is unclear whether the cut points we derived for weak grip strength are suitable for use in other settings. Our objective was to investigate differences in grip strength by world region using our data as a reference standard. Methods: we searched MEDLINE and EMBASE for reporting age- and gender-stratified normative data for grip strength. We extracted each item of normative data and converted it on to a Z-score scale relative to our British centiles. We performed meta-regression to pool the Z-scores and compare them by world region. Findings: our search returned 806 abstracts. Sixty papers met inclusion criteria and reported on 63 different samples. Seven UN regions were represented, although most samples (n = 44) were based in developed regions. We extracted 726 normative data items relating to 96,537 grip strength observations. Normative data from developed regions were broadly similar to our British centiles, with a pooled Z-score 0.12 SDs (95% CI: 0.07, 0.17) above the corresponding British centiles. By comparison, normative data from developing regions were clearly lower, with a pooled Z-score of −0.85 SDs (95% CI: −0.94, −0.76). Interpretation: our findings support the use of our British grip strength centiles and their associated cut points in consensus definitions for sarcopenia and frailty across developed regions, but highlight the need for different cut points in developing regions.

Physical activity levels across adult life and grip strength in early old age: updating findings from a British birth cohort

Introduction: observational studies do not always find positive associations between physical activity and muscle strength despite intervention studies consistently showing that exercise improves strength in older adults. In previous analyses of the MRC National Survey of Health and Development (NSHD), the 1946 British birth cohort, there was no evidence of an association between leisure time physical activity (LTPA) across adulthood and grip strength at age 53. This study tested the hypothesis that cumulative benefits of LTPA across mid-life on grip strength will have emerged by age 60–64. Methods: data from the MRC NSHD were used to investigate the associations between LTPA at ages 36, 43, 53 and 60–64 and grip strength at 60–64. Linear regression models were constructed to examine the effect of activity at each age separately and as a cumulative score, including adjustment for potential confounders and testing of life course hypotheses. Results: there were complete longitudinal data available for 1,645 participants. There was evidence of a cumulative effect of LTPA across mid-life on grip strength at 60–64. Compared with the third of participants who reported the least LTPA participation across the four time points, those in the top third had on average 2.11 kg (95% CI: 0.88, 3.35) stronger grip after adjustments. Conclusions: increased levels of LTPA across mid-life were associated with stronger grip at age 60–64, in both men and women. As these associations have emerged since age 53, it suggests that LTPA across adulthood may prevent decline in grip strength in early old age.

Prevalence and incidence of sarcopenia in the very old: findings from the Newcastle 85+ study

Recognition that an older person has sarcopenia is important because this condition is linked to a range of adverse outcomes. Sarcopenia becomes increasingly common with age, and yet there are few data concerning its descriptive epidemiology in the very old (aged 85 years and above). Our aims were to describe risk factors for sarcopenia and estimate its prevalence and incidence in a British sample of the very old.

The Epidemiology of Sarcopenia

The aim of this review is to describe the epidemiology of sarcopenia, specifically prevalence, health outcomes, and factors across the life course that have been linked to its development. Sarcopenia definitions involve a range of measures (muscle mass, strength, and physical performance), which tend to decline with age, and hence sarcopenia becomes increasingly prevalent with age. Less is known about prevalence in older people in hospital and care homes, although it is likely to be higher than in community settings. The range of measures used, and the cutpoints suggested for each, presents a challenge for comparing prevalence estimates between studies. The importance of sarcopenia is highlighted by the range of adverse health outcomes that strength and physical performance (and to a lesser extent, muscle mass) have been linked to. This is shown most strikingly by the finding of increased all-cause mortality rates among those with weaker grip strength and slower gait speed. A life course approach broadens the window for our understanding of the etiology of sarcopenia and hence the potential intervention. An example is physical activity, with increased levels across midadulthood appearing to increase muscle mass and strength in early old age. Epidemiologic studies will continue to make an important contribution to our understanding of sarcopenia and possible avenues for intervention and prevention.

Grip strength among community-dwelling older people predicts hospital admission during the following decade

BACKGROUND Lower grip strength on admission to hospital is known to be associated with longer stay, but the link between customary grip and risk of future admission is less clear. OBJECTIVE To compare grip strength with subsequent risk of hospital admission among community-dwelling older people in a U.K. setting. DESIGN Cohort study with linked administrative data. SETTING Hertfordshire, U.K. SUBJECTS A total of 2,997 community-dwelling men and women aged 59-73 years at baseline. METHODS The Hertfordshire Cohort Study (HCS) participants completed a baseline assessment between 1998 and 2004, during which grip strength was measured. Hospital Episode Statistics and mortality data to March 2010 were linked with the HCS database. Statistical models were used to investigate the association of grip strength with subsequent elective, emergency and long-stay hospitalisation and readmission. RESULTS There was a statistically significant negative association between grip strength and all classes of admission in women [unadjusted hazard ratio per standard deviation (SD) decrease in grip strength for: any admission/death 1.10 (95% CI: 1.06, 1.14), elective admission/death 1.09 (95% CI: 1.05, 1.13), emergency admission/death 1.21 (95% CI: 1.13, 1.31), long-stay admission/death 1.22 (95% CI: 1.13, 1.32) and unadjusted relative risk per SD decrease in grip strength for 30-day readmission/death 1.30 (95% CI: 1.19, 1.43)]. These associations remained significant after adjustment for potential confounding factors (age, height, weight for height, smoking, alcohol, social class). In men, unadjusted rates for emergency admission/death, long-stay admission/death and readmission/death were significantly associated with grip strength; associations that similarly withstood adjustment. CONCLUSION This study provides the first evidence that grip strength among community-dwelling men and women in the U.K. is associated with risk of hospital admission over the following decade.

Effects of Aerobic Exercise on Muscle Strength and Physical Performance in Community‐dwelling Older People from the Hertfordshire Cohort Study: A Randomized Controlled Trial

To the Editor: There is considerable interest in the role of physical activity interventions to address the age-related loss of skeletal muscle mass. Resistance exercise is consistently associated with improvement in muscle strength and physical performance (PP) in older adults but the influence of aerobic exercise on these outcomes is less clear. Studies of the influence of aerobic exercise on muscle have typically taken place among specific patient populations and less so in older people. We studied the effects of a fully supervised 12 week aerobic exercise intervention on muscle strength and PP among the community-dwelling healthy older men and women who participated in the Hertfordshire Physical Activity Intervention Trial (HPAT),1 a sub-study of the Hertfordshire Cohort Study.2

How to get started with a systematic review in epidemiology: an introductory guide for early career researchers

BackgroundSystematic review is a powerful research tool which aims to identify and synthesize all evidence relevant to a research question. The approach taken is much like that used in a scientific experiment, with high priority given to the transparency and reproducibility of the methods used and to handling all evidence in a consistent manner.Early career researchers may find themselves in a position where they decide to undertake a systematic review, for example it may form part or all of a PhD thesis. Those with no prior experience of systematic review may need considerable support and direction getting started with such a project. Here we set out in simple terms how to get started with a systematic review.DiscussionAdvice is given on matters such as developing a review protocol, searching using databases and other methods, data extraction, risk of bias assessment and data synthesis including meta-analysis. Signposts to further information and useful resources are also given.ConclusionA well-conducted systematic review benefits the scientific field by providing a summary of existing evidence and highlighting unanswered questions. For the individual, undertaking a systematic review is also a great opportunity to improve skills in critical appraisal and in synthesising evidence.

Sarcopenia, frailty and mortality: the evidence is growing

Sarcopenia is an area of intense research activity [1], and the condition has recently been recognised with an ICD-10 code. This reflects the considerable progress in operationalising a definition of sarcopenia, now widely viewed as the loss of muscle mass and function with age. The European Working Group recommended first checking for poor muscle function (slow gait speed or weak grip strength) and, if present, testing for low muscle mass [2]. They did not specify a single approach to the measurement of strength and muscle mass, which has allowed the framework to be implemented in numerous studies but has presented a challenge when trying to compare their findings [3]. More recently the Foundation for the Institutes of Health (FNIH) Biomarkers Consortium published cutpoints for grip strength and appendicular lean mass divided by body mass index (ALMBMI) [4]. To do this, they pooled data from nine US and European studies of communitydwelling older people and calculated the cut-points that best identified individuals with a gait speed of less than 0.8 m/s. As such their cut-points are intended to help clinicians to decide whether low muscle strength or mass may be playing a major part in a patient’s mobility problems. A key test for the FNIH muscle strength and mass cutpoints is whether they identify those at risk of future adverse outcomes. In six of the nine studies, they were able to look at incident mobility disability and all-cause mortality: both low grip and ALMBMI were associated with the former but only low grip with the latter [5]. The FNIH recommended further assessment of their cut-points in relation to ageing outcomes in other populations. In this issue of Age and Ageing, De Buyser and colleagues examine whether the FNIH cut-points predict all-cause mortality over a 15-year period in a cohort of 191 communitydwelling Belgian men [6]. They found that low ALMBMI was associated with an approximately 50% increased risk of mortality, while low grip strength had an increased risk that did not reach statistical significance. The small proportion of the sample with both low ALMBMI and low grip strength at baseline was at two-and-a-half times the risk of death compared to those with normal mass and strength. De Buyser and colleagues also tested if a simple measure of frailty, the Study of Osteoporotic Fractures (SOF) frailty index, was associated with mortality. Participants were considered to be pre-frail if they had one of the three criteria: inability to rise from a chair five consecutive times without using the arms, weight loss and poor energy; they were considered to be frail if they had two of the three. Pre-frail and frail individuals were at increased risk of death in a graded fashion. Overall, the area under the curve figures suggested a moderate ability of FNIH sarcopenia and SOF frailty to predict an individual’s risk of death. Finally, when combined in the same model, sarcopenia and frailty were independently associated with mortality risk. How can we interpret the findings of the study? For the FNIH grip strength cut-point, the authors did not find a statistically significant relationship with mortality, in contrast with the FNIH’s own analyses [5] and findings from previous studies [7, 8]. This difference may be explained by this study’s small sample size and in particular the small number (n = 27) of men with weak grip strength at baseline. For the cut-point for ALMBMI, the situation is less clear: here the authors did find a relationship, whereas the FNIH metaanalysis showed heterogeneity between studies and no overall pooled effect. Indeed measures of lean mass have previously shown little relation to ageing outcomes [9], although the recent use of ALMBMI instead of ALM divided by height squared does appear to be more informative [10]. The authors also investigated the SOF frailty index and found that it predicted mortality. There was only partial overlap between those with (pre)frailty and those with relevant sarcopenia measures (weak grip or low ALMBMI). This area of overlap likely reflects the impairment of physical function, which is common to both conditions [11]. Importantly, the current findings would support the use of both sarcopenia and frailty assessments by clinicians aiming to identify older people at increased risk of death, for example when weighing up the risks and potential benefits of an intervention [12]. There are other issues that it may be important to consider if implementing the FNIH cut-points in clinical practice. Dual energy x-ray absorptiometry scans may not be available for the assessment of ALMBMI, for example if seeing patients outside of the hospital setting, and in this regard, the separate analyses undertaken by FNIH and others for grip strength and ALMBMI are helpful. The cut-points have also been developed among mobile, community-dwelling older people. From existing work on grip strength, it is likely that the prevalence of individuals falling below the FNIH cut-points is likely to be much higher among those in hospital/institutional care settings [13] and the very old [14]. Areas for future work therefore include validating the FNIH cut-points in a range of settings for both men and