Associations Between Lifestyle Behaviors and Handgrip Strength in Community-Dwelling Older Women

1. Introduction

Handgrip strength is widely recognized as a simple and reliable indicator of overall muscle strength and physical function in older adults [1,2,3]. It has been extensively used as a clinical and epidemiological marker associated with adverse health outcomes, including frailty, disability, hospitalization, and mortality [4,5]. Large-scale population-based studies have also demonstrated strong associations between grip strength and all-cause mortality as well as chronic diseases [6].

Aging is accompanied by a progressive decline in muscle strength that is more pronounced in women than in men. Older women are particularly vulnerable to declines in muscle strength due to factors such as low baseline muscle mass, hormonal changes, and lifestyle-related factors. Therefore, identifying modifiable factors associated with the maintenance of muscle strength in older women is considerably important to preventing functional decline and extending healthy life expectancy.

Lifestyle factors play an important role in maintaining physical function in older adults. Previous studies have shown that physical activity, dietary habits, and sleep quality are associated with muscle strength and physical performance [7,8,9]. Additionally, social interaction and participation in daily activities contribute to physical function and well-being [10,11,12,13]. Multiple lifestyle behaviors also jointly influence physical function [14,15].

However, most previous studies have examined individual lifestyle factors in isolation, and few have simultaneously examined multiple lifestyle domains [16,17,18]. Moreover, the relationships between lifestyle factors and handgrip strength may be confounded by age, which is strongly associated with lifestyle behaviors and muscle strength. Therefore, it is important to examine these associations while appropriately accounting for age.

Furthermore, evidence specifically focused on community-dwelling older women is limited. Individuals who actively participate in community-based activities may exhibit distinct lifestyle characteristics that influence their physical function. Therefore, this study aimed to examine the associations between multiple lifestyle factors, including dietary status, exercise frequency, sleep quality, social interaction, and outing frequency, and handgrip strength among community-dwelling older women. Additionally, whether these associations remained significant after adjusting for age was investigated.

2. Materials and Methods

2.1. Study Design and Participants

This cross-sectional study included community-dwelling older women who participated in community-based meetings coordinated by the Matsuyama City Social Welfare Council between May and December 2024. Eligibility criteria for participation in the meetings included age 60 years or older and not being certified as requiring long-term care by the Japanese long-term care insurance system. Participants with missing data regarding key variables were excluded from the analysis.

2.2. Ethical Considerations

This study was approved by the Ethics Committee of Tokai Gakuen University (approval number: 2025-21) and conducted in accordance with the principles of the Declaration of Helsinki. All participants provided informed consent prior to participation.

2.3. Assessment of Handgrip Strength

Handgrip strength was measured using a digital handgrip dynamometer (T.K.K. 5401; Takei Scientific Instruments Co., Ltd., Niigata, Japan). Measurements were conducted by trained staff in accordance with a standardized protocol. Participants performed the test twice for each hand, and the average of the maximum values obtained for each hand was used for analysis. The measurement was performed while the participant was standing, with the arms naturally at the sides. Participants were instructed to exert maximal effort.

2.4. Classification of Handgrip Strength

Participants were categorized into tertiles (low, middle, and high) based on the distribution of handgrip strength among women, using the 33.3rd and 66.7th percentiles (cut-off values: 18.65 kg and 22.05 kg).

2.5. Assessment of Lifestyle Factors

Lifestyle factors were assessed using a structured questionnaire. Exercise frequency was categorized as high or low based on predefined criteria. Sleep quality was classified as good or poor according to the self-reported sleep status. Dietary status was categorized as good or poor based on dietary habits. Social interaction was classified as high or low based on the frequency of interpersonal communication. Outing frequency was categorized as active or inactive based on how often participants ventured outside.

2.6. Lifestyle Score

A composite lifestyle score was calculated by summing the number of healthy lifestyle factors (exercise, sleep, diet, social interaction, and outing frequency). The total score ranged from 0 to 5, and higher scores indicated healthier lifestyle behaviors. The lifestyle score was further categorized into tertiles (low, middle, and high) based on its distribution.

2.7. Statistical Analysis

Descriptive statistics of all variables were calculated. Continuous variables are presented as the mean ± standard deviation. Categorical variables are presented as numbers (percentage). Differences between handgrip strength tertiles were assessed using a one-way analysis of variance for continuous variables and the chi-square test for categorical variables.

To examine age-adjusted associations between lifestyle factors and handgrip strength, an analysis of covariance was performed with age as a covariate. Adjusted proportions and 95% confidence intervals of each group were estimated.

Additionally, the association between lifestyle score categories and handgrip strength was evaluated using the chi-square test. A trend across tertiles was assessed using linear-by-linear association.

All statistical analyses were performed using IBM SPSS Statistics version 30.0 (IBM Corp., Armonk, NY, USA). A two-tailed p<0.05 was considered statistically significant. All analyses were conducted according to a prespecified statistical analysis plan.

3. Results

Characteristics of the participants in each handgrip strength tertile are presented in Table 1.

Mean age differed significantly across tertiles. Participants in the low handgrip strength tertile were older than those in the middle and high handgrip strength tertiles (82.4 ± 6.0 vs. 78.6 ± 5.8 vs. 75.5 ± 6.0 years, respectively).

Exercise frequency did not differ significantly across tertiles (p = 0.065). In contrast, sleep quality differed significantly across tertiles. The proportion of participants who reported good sleep quality in the high tertile was higher than that in the low tertile (82.3% vs. 76.7%; p = 0.021). Dietary status was also significantly associated with handgrip strength. The proportion of participants who reported good dietary status in the middle and high tertiles was higher than that in the low tertile (97.1% and 97.0% vs. 93.8%; p=0.001).

Social interaction also differed significantly across tertiles. The proportion of participants who reported high levels of social interaction increased from the low tertile to the high tertile (low, 58.2%; middle, 66.9%; high, 72.8%; p=0.001). Outing frequency was also significantly associated with handgrip strength (p=0.001).

After adjusting for age (Table 2), dietary status (p=0.024), social interaction (p=0.001), and outing frequency (p=0.017) remained significantly associated with handgrip strength; however, sleep quality (p=0.073) and exercise frequency (p=0.060) did not. These age-adjusted associations are presented in Figure 1. The distribution of lifestyle scores across tertiles is shown in Figure 2.

Figure 2 shows the distribution of lifestyle scores across tertiles.

Additionally, lifestyle score categories were significantly associated with handgrip strength (Table 3). A clear dose–response relationship was observed across tertiles, indicating that higher lifestyle scores were associated with higher handgrip strength. This dose–response relationship is clearly illustrated in Figure 3 (p < 0.001).

4. Discussion

This study examined the associations between multiple lifestyle factors and handgrip strength among community-dwelling older women. The main finding was that dietary status, social interaction, and outing frequency were independently associated with handgrip strength even after adjusting for age.

These findings are consistent with those of previous studies that reported that nutritional factors play a central role in maintaining muscle function in aging populations [19,20,21]. Adequate nutrition is essential for preserving muscle mass and function, and poor dietary quality has been linked to sarcopenia and functional decline [22,23,24].

Similarly, social interaction and outing frequency were independently associated with handgrip strength. These results align with prior evidence that indicated that social engagement is associated with better health outcomes [25,26,27]. Reduced outing frequency has been linked to functional decline in older adults [10,28,29].

Importantly, a clear dose–response relationship was observed between lifestyle score and handgrip strength, suggesting that the accumulation of healthy lifestyle behaviors may contribute to better physical function. This finding supports previous studies that indicated that multiple healthy lifestyle behaviors have combined and cumulative effects on health outcomes [30,31]. In contrast, sleep quality and exercise frequency were not significantly associated with handgrip strength after adjusting for age. Attenuation of this association after age adjustment suggests that the relationship between sleep quality and handgrip strength may be largely explained by age. Additionally, it may reflect limitations in measurements because exercise frequency alone does not capture important aspects such as the intensity or duration of physical activity. These findings highlight the importance of multidimensional lifestyle approaches to maintaining physical function in community-dwelling older women.

This study had several strengths. First, it included a relatively large sample of community-dwelling older women, enabling stable statistical analysis. Second, multiple lifestyle domains were assessed simultaneously, thus providing a comprehensive evaluation of factors associated with physical function. Third, age-adjusted analyses were conducted because age is a major confounding factor.

However, several limitations of this study should be acknowledged. First, because of the cross-sectional design, causal relationships could not be established; therefore, the findings should be interpreted with caution. Second, participants were recruited from community-based meetings and may represent a relatively health-conscious population, which may have limited the generalizability of the results. Third, lifestyle factors were assessed using a self-reported questionnaire; therefore, recall bias could not be ruled out.

Dietary status, social interaction, and outing frequency among older women were independently associated with handgrip strength after accounting for age. Multidimensional lifestyle factors, particularly those related to nutrition and social engagement, may contribute to the maintenance of physical function in older populations.

5. Conclusions

In conclusion, dietary status, social interaction, and outing frequency were 　independently associated with handgrip strength among community-dwelling older women, even after adjustment for age. In addition, a clear dose–response relationship was observed between lifestyle scores and handgrip strength, suggesting that the accumulation of healthy lifestyle behaviors is linked to better physical function.

These findings underscore the importance of multidimensional lifestyle factors, particularly those related to nutrition and social engagement, in the maintenance of muscle strength in older adults. Although causal relationships cannot be established due to the cross-sectional design, the present results provide meaningful insights for developing community-based strategies aimed at preventing functional decline. Future longitudinal studies are warranted to confirm these associations.

6. Patents

The authors declare no patents.