Neck circumference is a highly reliable anthropometric measure in older adults requiring long-term care

Introduction

The worldwide population of people aged 60 years or older is expected to double by 2050, with significant health and economic consequences (Shlisky et al., 2017). With the aging of the population, increasing numbers of older adults will require long-term care; accordingly, care and support for older adults are becoming important issues (Abdi et al., 2019). Older adults requiring long-term care have higher rates of malnutrition (Sato et al., 2021). Malnutrition is associated with further decline in physical function (Reber et al., 2019), reduced activities of daily living (ADLs) (Mukundan et al., 2022), and increased mortality (Norman, Haß & Pirlich, 2021). This suggests the importance of early detection of poor nutritional status in older adults through screening, allowing for early intervention (Serón-Arbeloa et al., 2022).

Limb circumference measurement is commonly used as a simple nutritional screening assessment in facilities without specialized equipment (Weng et al., 2018). However, circumferential measurement of the extremities in older adults who require long-term care presents many challenges. For instance, proper evaluation of the circumference of the extremities is difficult in individuals with edema, resulting in overestimation of the circumference of the lower extremities (Ishida et al., 2019), and in those with limb contractures. Among anthropometric indices, measurement of the neck circumference is less time-consuming, and is less susceptible to limb impairment. Several studies have reported that neck circumference is associated with nutritional status (Wakabayashi & Matsushima, 2016) and swallowing-related muscle strength (Yoshida et al., 2019), and is also a predictive marker for sarcopenia (Sato et al., 2022) and frailty (Tanaka et al., 2020). Further, Lardiés-Sánchez et al. (2019) reported that the neck circumference is more accurate for nutritional screening than lower leg and upper arm circumferences in older adults requiring long-term care. This suggests that the neck circumference is a useful nutritional screening tool for older adults requiring long-term care.

Anthropometric methods have inherent limitations due to measurement error. Inter-rater reliability must be verified to clarify the clinical utility of anthropometry. However, the reliability of neck circumference measurement in older adults has not been clarified (LaBerge et al., 2009; Stomfai et al., 2011). We hypothesized that the neck circumference measurement as an assessment tool for older adults requiring long-term care is highly reliable. Therefore, this study aimed to clarify (1) the examiner reliability of neck circumference measurement in older adults requiring long-term care, and (2) the effect of edema on the measurement error in neck circumference.

Materials and Methods

Study setting and participants

Participants comprised older adults who were determined to be in need of support or care under the Japanese long-term care insurance system and used a day care rehabilitation facility for older adults (Yamada & Arai, 2020). All 146 participants using day care facility were approached in March 2023, and all users were able to give consent. Only 108 older adults were included in the study analysis. Exclusion criteria were as follows: (1) age under 65 years, (2) age over 100 years, (3) inability to measure extracellular water to total body water (ECW/TBW), and (4) missing data (Fig. 1).

Results

A total of 108 older adults (66 men and 42 women) participated in this study (Fig. 1). Table 1 summarizes the basic attributes and pre-existing medical conditions of the study participants.

The intra-rater reliability for neck circumference measurement was high, with ICC (1,1) >0.99, for both examiners A and B (Table S1). The inter-rater reliabilities for neck circumference measurement are shown in Table 2. The inter-rater reliability for neck circumference measurement in all participants was high, with ICC (2,1) = 0.98. The inter-measurement bias was 0.1 cm (95% LOA: −0.9 to 1.2 cm) (Fig. 2). Among participants with ECW/TBW ≥ 0.400 (edematous group), the inter-rater reliability for neck circumference was also high, with ICC (2,1) = 0.98. In addition, the inter-measurement bias was 0.2 cm (95% LOA: −0.8 to 1.1 cm) (Fig. 2).

No association was found between the ECW/TBW and inter-rater measurement absolute value of the difference (r = −0.01, p = 0.951) (Fig. 3).

Discussion

The present study evaluated the inter-rater reliability of neck circumference measurement in older adults requiring long-term care. We found that the inter-rater reliability for neck circumference measurement was ICC (2,1) = 0.98, indicating a high degree of reliability. Furthermore, differences within −0.9 to 1.2 cm in neck circumference values were shown to be acceptable as inter-examiner error. To our knowledge, this study is the first to validate the reliability of neck circumference measurement in older adults requiring long-term care.

Previous studies have shown that BMI is associated with neck circumference and is a screening tool for metabolic syndrome (Hingorjo, Qureshi & Mehdi, 2012; Kroll et al., 2017; Kim, Moon & Yun, 2021). Previous studies have also shown that a decrease in neck circumference is independently associated with sarcopenia (Sato et al., 2022). Neck circumference is also used as an indicator to assess non-communicable diseases, and it has been reported that increased neck circumference is associated with an increased risk of cardiovascular disease (Asil et al., 2021; Caro et al., 2019). While nutritional indices such as BMI may lead to overestimation of sarcopenia due to potential internal edema, Do, Kim & Kang (2022) reported that neck circumference predicts sarcopenia better than BMI in with predicted edema, such as in the case of patients undergoing peritoneal dialysis. Furthermore, Dogan, Ayhan & de Almeida (2023) found that neck circumference can predict sarcopenia as accurately as calf circumference—the standard screening tool for sarcopenia. This suggests that neck circumference may be a useful tool to assess sarcopenia among older people requiring long-term care.

Upper arm and calf circumferences are commonly used circumference measurements. A study of community-dwelling older adults by Foroughi et al. (2011) reported a high degree of concordance for upper arm circumference measurement, with an inter-examiner correlations (r) ranging 0.84 to 0.94. In addition, Jamaiyah et al. (2008) reported a 95% LOA of −0.9 to 0.4 cm and ICC of 0.998 for lower calf circumference measurement in adults aged 60 years or older, indicating high inter-rater reliability. Similar to these previous studies of circumference measurement, the present study results indicate neck circumference as a physical measurement index with high inter-rater reliability. Therefore, the results suggest that neck circumference can be used as a reliable tool in older adults requiring long-term care, even in those with contractures or trauma to the upper and lower extremities or who have difficulty dressing and undressing. Furthermore, the study confirmed high reliability in overhydrated older adults (ECW/TBW ≥ 0.400) and found no association between ECW/TBW and inter-rater differences. This suggests that the neck circumference measurement method is a reliable assessment tool for older adults suffering from a variety of conditions that cause excess water retention. This study reveals, for the first time, the intra- and inter-rater reliability of neck circumference to assess sarcopenia in older adults.

The present study has some limitations. First, this was a single-center study; further multicenter studies are needed for increased generalizability. Second, the measurements were taken by two experts working at the facility; therefore, the procedures used in this study cannot be used in a design in which three or more examiners measure the same participant. Furthermore, reliability may be reduced with larger numbers of examiners. Third, although the two examiners were blinded about each other’s measurements taken in this study—the order of which was also randomized—no counterbalancing was adopted. In the future, it would be desirable to adopt counterbalancing across the study sample. Finally, this study focused on a statistical tool; the final decision regarding the clinical application of the errors identified in this study is left to the researcher/clinician.

Conclusions

The present study found that neck circumference measurement shows high inter- and intra-examiner reliability in older adults requiring long-term care. It was also found to be reliable in those who presented with edema.

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