Patterns of multimorbidity in association with falls among the middle-aged and older adults: results from the China Health and Retirement Longitudinal Study

As a common geriatric syndrome, falls are the leading cause of injury and death among the elderly. Approximately 50% of people aged > 80 years have experienced a fall [1]. Moreover, fall frequency increased with age and aggravated frailty [2]. In China, fall incidence has increased as the ageing population has increased rapidly in the past two decades [3]. Old people experiencing falls are more vulnerable to environmental challenges and face an increased risk of adverse outcomes and heavy medical burdens [4]. Therefore, identifying the potential risk factors of falls is of great importance [5].

Chronic diseases are important risk factors of falls in the elderly, but most studies focused on the independent effect of a single chronic disease on falls. Multimorbidity is defined as the co-occurrence of ≥ 2 chronic diseases, and preventing multimorbidity has become a priority in primary care [6]. Despite the large burden of multimorbidity in China, there has been little focus on the effect of multimorbidity on falls.

Previous explorations of the relationship between multimorbidity and falls rarely investigated the relationship between different multimorbidity patterns and falls [7, 8]. Multimorbidity patterns refer to the classification of chronic diseases into different combinations based on the associations between them [9, 10]. Chronic diseases belonging to the same pattern might interact with each other and lead to a further decline in physical performance and cognitive function [11]. Several studies have demonstrated inconsistent associations of different multimorbidity patterns with functional impairment and physical performance, which suggested that these phenomena might also exist between falls and different multimorbidity patterns [12‐14]. However, there have been few investigations of the associations between multimorbidity patterns and falls in Chinese [15].

Accordingly, we determined the multimorbidity patterns in Chinese and the longitudinal associations between falls and multimorbidity and multimorbidity patterns based on a nationally representative cohort of middle-aged and old people in China. We expect that our findings will present medical workers and old people with more effective fall prevention suggestions.

In the present study, we identified four multimorbidity patterns (cardiac-metabolic, visceral-arthritic, respiratory, and mental-sensory) in a nationally representative sample of community-dwelling middle-aged and old Chinese. We determined that multimorbidity and each multimorbidity pattern were positively associated with an increased risk of falls.

In this study, participants with ≥ 2 chronic diseases were more likely to fall than those without chronic diseases, which was consistent with the results of Lawlor et al. and Immonen et al. [19, 20]. Immonen et al. [20] reported higher incident and relapse rates of falls as the number of chronic diseases increased, which indicated that chronic diseases might exert cumulative effects on the occurrence of falls. Frailty might explain the relationship between multiple diseases and falls [21, 22], where people with multiple diseases have accelerated catabolism and are more likely to be frail, which could increase the risk of falls. Polypharmacy is another possible explanation for these associations in people with multimorbidity. Polypharmacy was significantly related to falls, and the effect of drug interactions was more obvious in the elderly due to degradation of the drug absorption, metabolism, and elimination processes [23, 24]. Zia et al. reported that taking ≥ 4 drugs increased the incident rate of falls [25]. Our findings suggested that people with multiple chronic diseases should adopt effective interventions for preventing falls. Furthermore, medical workers should focus more on such patients.

Different studies reported differing numbers of multimorbidity patterns. A systematic review reported that the Western population had three common multimorbidity patterns: metabolic diseases, mental health problems, and musculoskeletal diseases [10]. Another systematic review of multimorbidity patterns in Asian populations revealed that Asians exhibited five common comorbidity patterns: cardiovascular and metabolic diseases, mental health problems, degenerative diseases, pulmonary diseases, and cancer [26]. In the present study, we identified four multimorbidity patterns. The reasons for these inconsistencies might be complicated. First, due to regional and ethnic differences, the prevalence of chronic diseases differs between study populations. Second, differing chronic diseases were included for determining the multimorbidity pattern. Third, different studies did not use consistent statistical analysis methods to determine the multimorbidity patterns.

The cardiac-metabolic pattern was the most common pattern in both Asian and Western populations [26, 27]. Diseases in the cardiac-metabolic pattern share common risk factors and can prompt each other mutually. The chronic diseases included in the cardiac-metabolic pattern, specifically hypertension, diabetes, and heart disease, could all increase the risk of falls [28‐30]. Patients with hemodynamic abnormalities were more likely to experience dizziness, which might lead to unconscious falls [31].

The diseases included in the respiratory pattern, such as chronic obstructive pulmonary disease (COPD) and pneumonia, can cause complications such as hypoxia, anemia, dehydration and electrolyte disorders, which can weaken a person’s compensatory capacity and balance ability and thereby increase the risk of falls [32]. Many studies demonstrated that chronic respiratory diseases, such as COPD and asthma, are closely related to falls [15, 22, 32, 33], and patients with multiple chronic respiratory diseases (respiratory pattern) have a higher risk of falls.

Our findings demonstrate that the effects of the number of chronic diseases and the factor scores within different multimorbidity patterns on falls were inconsistent and that the increased risk of falls was higher in the visceral-arthritic and mental-sensory patterns. This finding suggests that people who have more diseases within these two multimorbidity patterns face a higher risk of falls. There are several reasons for this phenomenon: in the visceral-digestive-arthritis pattern, pain, deformity, and dynapenia caused by musculoskeletal diseases, such as arthritis, further reduced patients’ motor abilities; therefore, these patients were more likely to fall [34, 35]. Furthermore, chronic kidney diseases prompted the occurrence of osteoporosis, which is highly related to falls and fractures in the elderly [35].

In the mental-sensory pattern, hearing loss and visual impairment make it difficult for patients to avoid obstacles and potential dangers when moving, so the patients are more likely to fall. Moreover, mental disorders, such as depression and anxiety, were highly correlated with falls [36, 37]. Fatigue and lack of motivation also led to a decline in functional ability, muscle strength, and balance ability, which might exert a cumulative impact on falls. Moreover, due to difficulties in the early identification of mental and sensory disorders, the diagnosis of such disorders in the elderly is likely to be delayed, thereby increasing the incidence of falls [36].

As our study population was from a rural or community setting, the findings may be able to provide some insight into primary care. The primary prevention of falls in the elderly should emphasize patients with multimorbidity, especially those with a high number of chronic conditions. Older adults with different multimorbidity patterns should be offered the appropriate fall prevention management measures focusing on the multimorbidity patterns with a higher risk of falls, such as the visceral-arthritis and mental-sensory patterns in this study. Early prevention should be implemented and a multidisciplinary fall prevention team should tailor fall prevention management plans for such patients. Communication between health practitioners and older adults with multimorbidity is also important, with a focus on safety education and awareness of fall prevention. Fall prevention research aimed at optimal and immediate transferability to real-world clinical practice is imperative.

The present study has several strengths. To the best of our knowledge, this is the first study to investigate the longitudinal association between different multimorbidity patterns and falls among Chinese. Second, the CHARLS collected data over a long duration from a nationally representative cohort of middle-aged and aged people in China, including detailed information on falls and most chronic diseases. Third, the EFA is the preferred method for exploring multimorbidity patterns.

Our study also has several limitations. First, the chronic diseases were self-reported and there might have been recall bias. Second, participants with missing data on chronic diseases were considered to have no chronic disease, which might have resulted in slight deviations in the multimorbidity prevalence and factor scores. Third, detailed information on the disease severity was not included in this study due to data availability.

The number of chronic diseases was positively associated with an increased risk of falls. Four multimorbidity patterns were identified in Chinese, which all increased the risk of falls. Early interventions are recommended for people with multiple chronic diseases to prevent falls. Future research is needed to elucidate the mechanism of the relationship between falls and multimorbidity and the multimorbidity pattern.