論文の公開元へRelationship of muscle strength, body composition and incident prediabetes among adults
概要
Introduction: Global prevalence of prediabetes and type 2 diabetes mellitus (T2DM) is rising rapidly. Early intervention in prediabetic individuals significantly reduces the risk of progression to T2DM. Thus, identifying individuals at higher risk of prediabetes would provide the best opportunity to implement preventive strategies. Shared risk factors for non-communicable diseases (NCDs), such as obesity, are well reported. However, contrary to data from western populations, studies from Sub-Saharan Africa (SAA) and Asia show that a substantial proportion of people with diabetes are not overweight or obese. One possible explanation might relate to the limitation of body mass index (BMI) since it lacks sensitivity for assessing disease risks, especially in people with normal or mildly elevated body weight. Low muscle strength has recently been suggested as another modifiable risk factor for T2DM. However, some studies do not report such an association, while others suggest reverse causation. Furthermore, no studies investigated the relationship between muscle strength and incident prediabetes to the best of my knowledge.
Objectives: The purpose of this study was to investigate the relationship between muscle strength, body composition, and incident prediabetes among adults. I, therefore, conducted studies in two different populations with the specific objectives outlined below.
Summary of study 1
Objective: To examine the longitudinal relationship of handgrip strength, a measure of muscle strength, with incident prediabetes among adults in Japan.
Methods: This was a cohort study instituted under the Center of Innovation (COI) program of Japan, aiming to improve the population's health status. The study was conducted in Ibaraki prefecture, whose capital city, Mito, is situated about 125 kilometers north-east of Tokyo. Most of the study participants belonged to the Japan Agriculture Cooperative of Ibaraki (JA Ibaraki). Participants were invited to attend annual medical examinations organized in partnership with JA at the regional hospital (Mito-Kyodo Hospital) and outreach services in the area or attend medical examinations organized by employers, with an annual attendance of 5000 individuals.
The study recruited individuals without prediabetes and diabetes attending lifestyle-related medical examinations between April 2016 and March 2017 (n = 2054). A standardized self- administered questionnaire of 22 items recommended by the Japan Ministry of Health, Labor, and Welfare was used to collect lifestyle-related information and medical history. After that, anthropometric measures, blood pressure fasting blood samples, and handgrip strength measures were taken. Individuals who came for the follow-up medical examinations between April 2018 and March 2019 were included in the analysis (n = 1075).
Results: One hundred sixty-nine individuals (15.7%) developed prediabetes after a mean follow- up of 24.2 months (SD = 1.9 months). Multivariable adjusted hazard ratios (aHR) of new prediabetes cases were calculated using Cox regression. Higher baseline relative handgrip strength predicted a lower risk (aHR [95% CI] = 0.38 [0.21–0.71] of prediabetes incidence among adults. Importantly, relative handgrip strength predicted new prediabetes cases among normal-weight individuals (aHR [95% CI] = 0.39 [0.16–0.96]).
Summary of study 2
Objective: To assess the association of body composition, muscle strength, and quality with prediabetes and T2DM among adults in Malawi.
Methods: This was a cross-sectional study nested in a follow-up study of prediabetic and prehypertensive individuals identified during an extensive NCDs survey in Malawi, which enrolled adults from two defined geographical areas within Karonga District and Lilongwe city. The Malawi Epidemiology and Intervention Research Unit (MEIRU) conducted the baseline NCDs survey between May 16, 2013, and Feb 8, 2016. In the follow-up study, participants were interviewed, had anthropometry, handgrip strength, blood pressure measured, and had fasting blood samples collected. A total of 261 participants were recruited between November 2018 and February 2019.
Results: The mean (SD) age of participants was 49.7 (13.6) years, and 54.0% were between 40 and 59 years. The mean (SD) absolute handgrip strength and relative handgrip strength were 28.8 (7.3) kg and 1.16 (0.40) kg/BMI, respectively, and the mean relative handgrip strength differed significantly (p<0.001) by T2DM status. Relative handgrip strength was well correlated with anthropometric and body composition measures such as waist circumference (r=-0.510, P<0.001), hip circumference (r=-0.572, P<0.001), body fat (r=-0.501, P<0.001), muscle mass (r=-0.521, P=<0.001), and muscle quality (r=0.215, P=0.037). In the unadjusted model, the odds ratio (OR) of prediabetes and T2DM per unit increase of relative handgrip strength was 0.12 [95% CI; 0.04- 0.33]. The result remained significant after adjusting for age (continuous), sex, place of study, hypertension, dyslipidemia, and level of education (AOR [95% CI]; 0.19 [0.03-0.95]).
Discussion:
This study found that lower baseline relative handgrip strength predicts a higher risk of prediabetes incidence among adults in Japan. This study's important finding was that relative handgrip strength predicted a lower and significant risk of prediabetes incidence among individuals with normal weight (BMI 18.5–24.9 kg/m2). This study continued to demonstrate this association among participants from the urban and rural areas of Malawi, where it was found that relative handgrip strength is associated with prediabetes and type 2 diabetes mellitus. The findings demonstrated the utility of handgrip strength measurements among sub-Saharan Africa populations.
This simple muscle strength measure is also well correlated with anthropometric and body composition measures among the participants. Additionally, relative handgrip strength was associated with other cardiovascular disease biomarkers. Body mass index alone has a limitation in assessing body composition since it lacks sensitivity for assessing disease risks, especially in people who have normal or mildly elevated BMI. Therefore, handgrip grip strength measurement would provide an opportunity for prediabetes and type 2 diabetes risk screening. Handgrip strength testing is cheap, non-invasive, and is easy to conduct in fieldwork, which would make its adoption in health examinations effortless. Furthermore, like body mass index, participants quickly understood their handgrip strength measurement outcome, which would motivate them to change their lifestyle.
Conclusions:
The use of handgrip strength, a simple measure of muscle strength, may have utility in identifying individuals at high risk of prediabetes who can then be targeted for intervention. Muscle strength may be uniquely important in stratifying prediabetes and type 2 diabetes risk among normal-weight adults considering BMI limitations. Participants of medical examinations could be motivated to improve muscle strength after understanding the risk that lower relative handgrip strength may indicate future prediabetes incidence and risk of type 2 diabetes.
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