The prevalence of age-related hearing loss has increased as the world population ages, resulting in a significant public health concern known as age-relate hearing loss. This decline in hearing not only impacts the overall well-being of patients, but it is also closely linked to the emergence of cognitive decline. Nevertheless, there remains a dearth of efficient prognostic instruments for promptly detecting age-related hearing loss in individuals with a heightened likelihood of cognitive decline in clinical settings. Traditional prediction models typically rely on clinical performance and lack objective data, resulting in limited predictive power and accuracy when dealing with large-scale, high-dimensional clinical data. In contrast, machine learning models are well-equipped to tackle these challenges. We extracted clinical objective data from the NHANES database using various machine learning algorithms. Subsequently, we employed one-way regression analysis to identify 15 indicators encompassing basic individual characteristics, lifestyle factors, and biochemical markers. We then applied LASSO regression to identify the factors that exhibited significant predictive value for cognitive impairment in elderly patients with hearing loss. A prediction model of cognitive impairment in elderly deaf people was constructed using five factors: education level, alkaline phosphatase, globulin, creatinine, and eosinophil percentage. Among the models evaluated, the XGB model consistently performs well in both the training and test sets. Although its performance decreases in the external validation set, the model still demonstrates more than moderate discriminative ability. This suggests that the model has reasonable predictive accuracy when applied to real clinical data.
The impact of cognitive reserve on cognitive impairment has been the focus of much research. Educational attainment, a significant indicator of cognitive reserve, has been demonstrated to have a substantial effect on cognitive impairment [15], which aligns with our study findings. There is a correlation between higher levels of education in older persons with hearing loss and a slower rate of cognitive decline. This correlation can be attributed to the positive impact of education on cognitive complexity and coping strategies. Hearing impairment has a negative impact on the ability of older individuals to engage in social activities and communicate effectively. This typically results in social challenges, which can further worsen cognitive decline[16]. Individuals with a greater degree of education are likely to have a larger social circle. This can be beneficial in maintaining a higher level of social engagement, even when experiencing hearing loss. Consequently, this can help reduce the adverse cognitive effects associated with hearing loss. When cognitive impairment arises, individuals with a higher level of education may be able to use their existing brain functions more effectively or discover alternative pathways for cognitive processing. This can lead to improved adaptation and resistance, ultimately enhancing an individual's ability to withstand cognitive decline[17]. For instance, these persons prioritize their health and are more inclined to actively pursue medical assistance and utilize assistive listening devices[18], such as hearing aids. Additionally, they are more inclined to pay closer attention to and comprehend information regarding hearing preservation. Consequently, they are more likely to adopt proactive measures at an earlier stage to mitigate the progression of hearing loss and its effects on cognitive function. Therefore, the level of education achieved may help mitigate the negative effects of hearing loss on cognitive functioning in older individuals. This is achieved by increasing cognitive reserve, improving social interactions, promoting healthy behaviors and psychological adjustments. Including this variable in the analysis enhances our understanding of the intricate connection between hearing loss and cognitive impairment.
Recent study has seen a growing number of scientists investigating the connection between liver and kidney function and cognitive decline. The liver and kidneys are vital metabolic organs in the body that are crucial for maintaining homeostasis and removing metabolic waste. If the function of these organs is compromised, it can have an impact on brain health and cognitive performance. Alkaline phosphatase and creatinine were identified as indicators of cognitive impairment in this investigation. An increased level of alkaline phosphatase in the body may indicate the existence of chronic illnesses, such as bone disease or impaired liver function, which might indirectly impact cognitive performance, particularly in older individuals. Research has indicated a potential correlation between bone health and cognitive performance[19]. For instance, an imbalance in the regulation of calcium metabolism and a lack of vitamin D may be connected to a deterioration in cognitive function, and both factors are indirectly linked to an increase in alkaline phosphatase activity[20]. Liver insufficiency can result in the buildup of toxins, metabolites, and various neurological disorders, which can impact brain function and hearing, thereby affecting cognitive performance[21, 22]. Similarly, hearing loss can also decrease the efficiency of nerve conduction, thereby affecting brain structure and function, including cognitive performance[23]. Creatinine levels serve as a crucial marker for evaluating the state of kidney function, and insufficient kidney function is regarded as a risk factor for hastened cognitive decline [24]. Renal insufficiency is linked to elevated levels of inflammation in the body, which can have a negative effect on vascular health by encouraging the development of atherosclerosis [25], including in the blood arteries of the brain. Hearing loss has been linked to impaired intracranial vascular condition, which can impact the circulation of blood to the ears and brain, consequently affecting both hearing and cognitive abilities[26]. Maintaining proper electrolyte balance and acid-base balance in the body is crucial for normal nerve conduction and brain function[27]. Elevated levels of creatinine may indicate a disruption in these balances, potentially impacting the function of auditory nerves and cognitive areas of the brain. Creatinine and alkaline phosphatase likely play a role in the connection between hearing loss and cognitive impairment through various physiological and pathological routes. Gaining a comprehensive understanding of these mechanisms would not only clarify the biological foundation of the cognitive impacts of hearing loss, but also offer crucial insights for the creation of specific preventative and treatment approaches. Future research will focus on thoroughly investigating the significance of these indicators in order to gain a comprehensive understanding of and effectively manage cognitive decline in older individuals.
Chronic inflammation has been established to be one of the key risk factors for cognitive impairment, which is consistent with the results of this study that found a link between globulin and eosinophil percentages and cognitive impairment. Both may play a bridge function between hearing loss and cognitive impairment. Changes in globulin and eosinophil percentage can reflect the body's inflammatory state or immune function, and their elevation usually reflects the presence of chronic inflammation or increased immune activity in the body, alterations that are thought to correlate with hearing loss and cognitive impairment[28]. Hearing loss itself is connected with increased levels of systemic inflammation, and inflammatory states may impact the health of auditory circuits. For example, otitis media can aggravate hearing loss, which can disrupt hearing-related cognitive processing, such as language comprehension and speech processing [29, 30]. On the other side, social isolation and communication difficulties due to hearing loss may induce a chronic stress reaction, which in turn increases the body's inflammatory response and impacts brain function, including memory and learning ability[31]. A chronic inflammatory condition will impair the integrity of the blood-brain barrier, allowing substances that would not usually enter the brain, such as inflammatory mediators, to enter the brain and impact the function and survival of nerve cells[32]. Globulin and eosinophil percentages as inflammatory indicators may reflect this altered barrier function. In addition, hearing loss may make it essential for older persons to commit more cognitive resources to interpreting language in everyday communication, which would raise their cognitive load[33]. Prolonged high cognitive load leads to overconsumption of cognitive resources and accelerates cognitive decline, in a process in which the body's immunological regulation and inflammatory response may further impact the management and allocation of cognitive resources[34]. This finding of peripheral inflammatory indicators such as globulins and eosinophils as predictors could help identify underlying inflammatory or immune-mediated pathological processes that may be co-factors of hearing loss and cognitive decline, providing clues for the development of more effective treatment and management strategies.
To summarize, the importance of five indicators - educational level, alkaline phosphatase, creatinine, eosinophil percentage, and globulin - offers us fresh insights into potential connections between cognitive reserve, hepatic and renal abnormalities, and inflammatory and immune status with cognitive impairment in elderly individuals with hearing loss. This discovery offers valuable insights for further investigating the causes of the disease and developing strategies to enhance our understanding and avoid the onset of cognitive decline in elderly individuals with hearing loss.
Limitation
The study yields valuable insights, although it is important to understand certain limitations. Initially, our investigation employed a cross-sectional design, which precluded us from establishing causation. Furthermore, the data used for training the model were acquired retrospectively from a database, which had a slight impact on the diversity of variables. Future studies should utilize large-sample, multicenter prospective cohorts and conduct a full assessment of cognitive impairment to improve the prediction of cognitive impairment in the elderly population with hearing loss.