Association between metabolic syndrome and risk of both prevalent and incident frailty in older adults: Findings from The Irish Longitudinal Study on Ageing (TILDA)

Association between non-insulin-based insulin resistance indicators and frailty progression: a national cohort study and mendelian randomization analysis

BACKGROUND

Insulin resistance (IR) is linked to an increased risk of frailty, yet it remains unclear whether the non-insulin-based IR indicators are associated with frailty trajectories and physical function decline. It aimed to examine the associations of triglyceride-glucose (TyG) index, metabolic score for insulin resistance (METS-IR), estimated glucose disposal rate (eGDR) and with long-term deficit-accumulation frailty trajectories and physical function decline.

METHODS

Data from 6722 participants in the China Health and Retirement Longitudinal Study (CHARLS) were analyzed. Baseline TyG index, METS-IR, eGDR, along with the frailty index (FI) over nine years, were calculated. FI trajectories were assessed using group-based trajectory model (GBTM). Logistic regression models were used to analyze the associations between IR indicators with FI trajectory and frailty risk. Restricted cubic splines (RCS) models were utilized to detect potential dose-response associations. Linear mixed-effects model was used to evaluate associations with FI development speed. Age, gender, educational level, marital status, smoking status, drinking status, life satisfaction, social activity and sleep duration were adjusted. Additionally, a two-sample Mendelian randomization (MR) was performed to assess the causality of observed associations.

RESULTS

Three FI trajectories including low-stable frailty, moderate-increasing frailty, and accelerated rising frailty were identified. Regarding the frail risk, each SD increment in TyG index was associated with a 16.1% increase in the risk of frailty (OR = 1.161; 95%CI: 1.092, 1.235). An inverse association was observed for eGDR with the OR (95%CI) being 0.741 (0.696, 0.788). A linear relationship was observed between baseline TyG index and frailty risk (P nonlinear = 0.696), but nonlinear association patterns for eGDR (P nonlinearity < 0.010) and METS-IR (P nonlinearity < 0.010). Each SD increment of TyG index was associated with greater FI increase (β = 0.005 SD/y; 95%CI = 0.002, 0.008 SD/y; P < 0.001). A similar association pattern was observed for METS-IR, and participants in the highest quartile of METS-IR showed significantly greater FI progression, with β value of 0.013 (95% CI = 0.004, 0.022). Each SD increment of eGDR was associated with a slower increase in FI (β=-0.006 SD/y, 95% CI=-0.009, -0.003 SD/y; P < 0.001). Participants in the highest quartile of eGDR presented a lower annual change in FI compared with participants in quartile 1 group during follow-up (β=-0.013 SD/y, 95% CI=-0.022, -0.005 SD/y; P for trend = 0.001). Similar findings were observed for physical function decline. Findings from MR analysis showed a causal relationship between higher TyG index and increased risk of frailty (β = 0.214, 95% CI = 0.079, 0.349; P = 0.002).

CONCLUSIONS

The non-insulin-based IR indicators, including TyG index, METS-IR and eGDR, were independently associated with the frailty progression and physical function decline. Monitoring and managing abnormal glucose metabolism should be recommended as a part of comprehensive strategies to prevent or delay the progression of frailty.

Nutritional specificity of frailty: from epidemiological and clinical evidence to potential mechanisms

PURPOSE OF REVIEW

Considering the ageing of the population, age-related syndromes, such as frailty, are prominent. In this context, nutrition is a modifiable factor considered a key nonpharmacological approach to prevention and treatment. Yet, its contribution to the frailty pathophysiology is conflicting in the literature. This paper discusses the recent literature (January 2023-June 2024) on the implication of nutrition in frailty management.

RECENT FINDINGS

Malnutrition is one of the main frailty risk factors. Proteins are the targeted macronutrient for their effects on muscle anabolism, not only in terms of quantity consumed but also in terms of sources. The diversity in plant and animal sources demonstrates better results than relying on a single source. More globally, anti-inflammatory and antioxidant diets are associated with a lower risk of frailty, like the Mediterranean Diet and specific food groups, like seafood, nuts, and seeds. Nutrition is pivotal in frailty prevention and treatment, and multidomain interventions providing exercises seem to yield even better results.

SUMMARY

Diverse protein sources and anti-inflammatory and antioxidant diets associated with exercises are the primary recommendations for frailty prevention and treatment. However, there is a need to evaluate how to achieve and maintain this healthy behaviour in real life.

Association of platelet-to-HDL cholesterol ratio with frailty and all-cause mortality

BACKGROUND

Frailty often requires intensive care, and the admission outcomes of frail patients are often poor. However, owing to the lack of reliable diagnostic indicators, quickly identifying frailty is challenging. The present study aimed to explore the associations of the platelet/high-density lipoprotein cholesterol ratio (PHR; a novel inflammatory indicator) with frailty and all-cause mortality.

METHODS

The present study analyzed data from the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2018. Frailty was assessed on the basis of the 49-item Frailty Index. The associations of the PHR with frailty and long-term survival prognosis were explored through weighted logistic regression, weighted restricted cubic spline (RCS), and weighted Cox regression, with adjustments for demographic factors, lifestyle, blood lipids, medication history, and complications. In addition, subgroup and interaction analyses were conducted. Finally, several sensitivity analyses were performed.

RESULTS

A total of 15,615 adult participants were included, with 7,928 women (53.63%) and an average age of 60.76 years. After fully adjusting for confounding variables, the prevalence of frailty in the highest PHR quartile group of was significantly greater than that in the lowest quartile group (OR: 1.23, 95% CI: 1.04-1.47; P = 0.02). The RCS showed that the inflection point was 166.7. Before and after the inflection point, the PHR was negatively associated (OR: 0.88, 95% CI: 0.80-0.97, P = 0.01) and positively associated (OR: 1.10, 95% CI: 1.02-1.19, P = 0.01) with frailty, respectively. Subgroup analysis suggested that the association between PHR and frailty was stronger in women than in men. A total of 5,544 frail participants were included in the survival analysis. The RCS revealed that the PHR was associated with the all-cause mortality risk of frail participants in a U-shaped manner, with an inflection point of 240.4. Before and after the inflection point, the PHR decreased (HR: 0.89, 95% CI: 0.81-0.97, P = 0.01) and the all-cause mortality risk increased (HR: 1.08, 95% CI: 1.02-1.14, P = 0.01), respectively.

CONCLUSION

The present study suggests that there is a J-shaped association between PHR and frailty in the adult population of the United States and that the association between the PHR and frailty is stronger in women. In addition, the PHR has a U-shaped relationship with the all-cause mortality risk of frail patients.

Association of metabolic syndrome severity with frailty progression among Chinese middle and old-aged adults: a longitudinal study

BACKGROUND

The binary diagnosis of Metabolic Syndrome(MetS) fails to accurately evaluate its severity, and the association between MetS severity and frailty progression remains inadequately elucidated. This study aims to clarify the relationship between the severity of MetS and the progression of frailty among the middle-aged and elderly population in China.

METHOD

Participants from the 2011-2018 China Health and Retirement Longitudinal Study(CHARLS) were included for a longitudinal analysis. The study employs a frailty index(FI) based on 32 health deficits to diagnose frailty and to assess FI trajectories. An age-sex-ethnicity-specific MetS scoring model (MetS score) was used to assess metabolic syndrome severity in Chinese adults. The Cumulative MetS score from 2012 to 2015 was calculated using the formula: (MetS score in wave 1 + MetS score in wave 3) / 2 × time(2015 - 2012). The association between MetS score, Cumulative MetS score, and the risk and trajectory of frailty were evaluated using Cox regression/logistic regression, and linear mixed models. Restricted Cubic Splines(RCS) models were utilized to detect potential non-linear associations.

RESULTS

A higher MetS score was significantly associated with an increased risk of frailty(HR per 1 SD increase = 1.205; 95%CI: 1.14 to 1.273) and an accelerated FI trajectory(β per 1 SD increase = 0.113 per year; 95%CI: 0.075 to 0.15 per year). Evaluating changes in MetS score using a Cumulative MetS score indicated that each 1 SD increase in the Cumulative MetS score increased the risk of frailty by 22.2%(OR = 1.222; 95%CI: 1.133 to 1.319) and accelerated the rate of increase in FI(β = 0.098 per year; 95%CI: 0.058 to 0.138 per year). RCS model results demonstrated a dose-response curve relationship between MetS score and Cumulative MetS score with frailty risk. Stratified analysis showed consistency across subgroups. The interaction results indicate that in males and individuals under aged 60, MetS score may accelerate the increase in FI, a finding consistent across both models.

CONCLUSIONS

Our findings underscore the positive correlation between the severity of MetS and frailty progression in the middle-aged and elderly, highlighting the urgent need for early identification of MetS and targeted interventions to reduce the risk of frailty.

Long-term insulin resistance is associated with frailty, frailty progression, and cardiovascular disease

BACKGROUND

Insulin resistance and diabetes are associated with an increased risk of frailty, and frailty is associated with cardiovascular disease and premature mortality. We aim to investigate the impact of long-term insulin resistance trajectories on future frailty and cardiovascular risk among young adults.

METHODS

In total, 3168 participants with a 30-year follow-up period. The baseline period covered the first 15 years as the exposure period. Insulin resistance was determined using the homeostasis model assessment for insulin resistance (HOMA-IR), and three trajectories (low, moderate, and high) were constructed. The subsequent 15 years constituted the event accrual period. Frailty was assessed using a deficit accumulation mode, and cardiovascular outcomes were obtained from the 15-year event accrual period.

RESULTS

The mean age of all 3168 participants was 41.0 (37.0-43.0) years, with 1750 (55.2%) being women. Participants in the high level of insulin resistance trajectory had an increased prevalence of frailty (OR: 1.55, 95% CI: 1.05-2.30, P = 0.028). Although no statistically significant associations were observed after full adjustment, single-factor analysis indicated association between the moderate and high trajectories and frailty progression. Additionally, participants with high level of insulin resistance trajectory were associated with an increased risk of cardiovascular disease, coronary heart disease, and stroke. A notable correlation between HOMA-IR trajectory and cardiovascular diseases was still discernible within the subgroup where the frailty index ≥0.12 (HR: 2.12, 95% CI: 1.17-3.83, P = 0.013) (P for interaction >0.05).

CONCLUSIONS

Long-term high level of insulin resistance is associated with high prevalence of frailty, and an increased risk of cardiovascular events. Emphasizing the importance of early prevention and intervention for abnormal glucose metabolism in young adults to prevent frailty and cardiovascular disease.

The intersection of frailty and metabolism

On average, aging is associated with unfavorable changes in cellular metabolism, which are the processes involved in the storage and expenditure of energy. However, metabolic dysregulation may not occur to the same extent in all older individuals as people age at different rates. Those who are aging rapidly are at increased risk of adverse health outcomes and are said to be "frail." Here, we explore the links between frailty and metabolism, including metabolic contributors and consequences of frailty. We examine how metabolic diseases may modify the degree of frailty in old age and suggest that frailty may predispose toward metabolic disease. Metabolic interventions that can mitigate the degree of frailty in people are reviewed. New treatment strategies developed in animal models that are poised for translation to humans are also considered. We suggest that maintaining a youthful metabolism into older age may be protective against frailty.

The Association between Circadian Syndrome and Frailty in US adults: a cross-sectional study of NHANES Data from 2007 to 2018

PURPOSE

Frailty and Circadian Syndrome (CircS) are prevalent among the elderly, yet the link between them remains underexplored. This study aims to examine the association between CircS and frailty, particularly focusing on the impact of various CircS components on frailty.

MATERIALS AND METHODS

We conducted a cross-sectional analysis using data from the National Health and Nutrition Examination Survey (NHANES) spanning 2007 to 2018. The 49-item Frailty Index (FI) was employed to assess frailty. To understand the prevalence of CircS in relation to frailty, we applied three multivariate logistic regression models. Additionally, subgroup and interaction analyses were performed to investigate potential modifying factors.

RESULTS

The study included 8,569 participants. In fully adjusted models, individuals with CircS showed a significantly higher risk of frailty compared to those without CircS (Odds Ratio [OR] = 2.18, 95% Confidence Interval [CI]: 1.91-2.49, p < 0.001). A trend of increasing frailty risk with greater CircS component was observed (trend test p < 0.001). Age (p = 0.01) and race (p = 0.02) interactions notably influenced this association, although the direction of effect was consistent across subgroups. Sensitivity analysis further confirmed the strength of this relationship.

CONCLUSION

This study identifies a strong positive correlation between CircS and frailty in the elderly. The risk of frailty escalates with an increasing number of CircS components. These findings highlight the intricate interplay between circadian syndrome and frailty in older adults, offering valuable insights for developing targeted prevention and intervention strategies.

Association between physical frailty, circadian syndrome and cardiovascular disease among middle-aged and older adults: a longitudinal study

BACKGROUND

Physical frailty (PF) and circadian syndrome (CircS) are proposed as novel risks for cardiovascular disease (CVD), but little attention is paid to their combined impact on CVD. This study aimed to investigate the association of PF, CircS and CVD in middle-aged and older adults.

METHODS

The sample comprised 8512 participants aged at least 45 years from the China Health and Retirement Longitudinal Study (CHARLS) 2011. PF was examined by the physical frailty phenotype scale. CircS was assessed by the components of the International Diabetes Federation (IDF) MetS plus short sleep duration and depression. The cut-off for CircS was set as ≥ 4. CVD was defined as the presence of physician-diagnosed heart disease and/or stroke. A total of 6176 participants without CVD recruited from CHARLS 2011 and were followed up in 2018.

RESULTS

The prevalence of CVD in total populations, neither CircS or PF, PF alone, CircS alone and both CircS and PF were 13.0%, 7.4%, 15.5%, 17.4%, and 30.2%, respectively. CircS was more likely to be PF [OR (95%CI): 2.070 (1.732 ∼ 2.472)] than those without CircS. Both CircS alone [OR (95% CI): 1.954 (1.663 ∼ 2.296)], and coexisting CircS and PF [3.508 (2.739 ∼ 4.494)] were associated with CVD. Longitudinal analysis showed that individuals with both CircS and PF (HR: 1.716, 95%CI: 1.314 ∼ 2.240) and CircS alone [1.520 (1.331 ∼ 1.737)] were more likely to have new onset CVD than neither CircS or PF peers.

CONCLUSION

PF and CircS together are associated with higher CVD risk, which provided new evidence for a strong relation that warrants attention to assessing PF and CircS and in community to promote healthy aging.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

Metabolic syndrome accelerates epigenetic ageing in older adults: Findings from The Irish Longitudinal Study on Ageing (TILDA)

Metabolic syndrome (MetS) is a risk factor for the development of diabetes, cardiovascular disease, and all-cause mortality. It has an estimated prevalence of 40 % among older adults. Epigenetic clocks, which measure biological age based on DNA methylation (DNAm) patterns, are a candidate biomarker for ageing. GrimAge is one such clock which is based on levels of DNAm at 100 Cytosine-phosphate-Guanine (CpG) sites. This study hypothesised that those with MetS have 'accelerated ageing' (biological age greater than their chronological age) as indexed by GrimAge. This study examined MetS's association with GrimAge age acceleration (AA) using data from a subsample of 469 participants of the Irish Longitudinal Study on Ageing (TILDA). MetS was defined by National Cholesterol Education Program Third Adult Treatment Panel (ATP III) and International Diabetes Foundation (IDF) criteria, operationalised using the conventional binary cut-off, and as a count variable ranging from 0 to 5, based on the presence of individual components. This study also explored inflammation (as measured by C reactive protein) and metabolic dysfunction (as measured by adiponectin) as possible mediating factors between MetS and GrimAge AA. We found that MetS as defined by IDF criteria was associated with GrimAge AA of 0.63 years. When MetS was treated as a count, each unit increase in MetS score was associated with over 0.3 years GrimAge AA for both ATP III and IDF criteria. Inflammation mediated approximately one third of the association between MetS and GrimAge AA, suggesting that chronic subclinical inflammation observed in MetS has a relationship with DNAm changes consistent with a faster pace of ageing. Metabolic dysfunction mediated the association between MetS and GrimAge AA to a lesser extent (16 %). These data suggest that chronic subclinical inflammation observed in MetS has a relationship with DNAm changes consistent with a greater pace of ageing.