HOME

Cognitive decline is growing public health concerns for aging population worldwide [1]. Mild cognitive impairment (hereafter, MCI) is a syndrome defined as cognitive decline greater than that expected for an individual’s age and education level but that does not interfere notably with activities of daily life [1, 2]. MCI represents early-stage dementia which is a leading cause of disability, institutionalization, and mortality; therefore, it could have a tremendous impact on both individual and society [2, 3].

As limited effective treatment alternatives for MCI and dementia are currently available, identification of risk or protective factors, especially modifying factors, could provide chance for preventing the disorder. Among the proposed protective factors, leisure activities are the most widely studied [4-6]. A cohort study conducted in Finland suggested that leisure-time physical activity at midlife is associated with a decreased risk of dementia [7]. Engaging in leisure activities is compatible with alcohol consumption and heavy drinkers have higher participation rates of outdoor activities [8, 9]. Alcohol drinking has been proposed as a possible risk factor for cognitive impairment [10].

Previous studies have focused on the effect of only physical activities among leisure activities on cognitive function, although there exists evidence showing that other types of leisure activities, such as mental and social activities, also have beneficial effects on a variety of health outcomes [5]. In addition, previous studies have only shown evidence of the individual effects of leisure activity and alcohol drinking on MCI [3, 10]; however, no study has investigated the joint effects of leisure activity and alcohol consumption on MCI. Because engaging in leisure activities is associated with alcohol drinking, their co-exposure could have a greater or mitigated effect than individual effect. Therefore, the joint effects of these factors on cognitive function need to be addressed.

Using data from the nationwide representative 2019 Korea Community Health Survey (KCHS), this study investigates the individual and joint effects of leisure activity and alcohol drinking on MCI.

This study illustrates the individual and joint effects of the leisure activity and alcohol drinking on MCI using a representative sample of the Korea population in 2019 KCHS. Leisure activity decreased the OR for MCI, and increasing alcohol drinking frequency was associated with higher OR for MCI. In addition, we found that the effect of drinking alcohol on MCI depends on whether or not engaging in leisure activities. As alcohol drinking frequency increased, people engaging in leisure activity showed more increment of the OR for MCI than not engaging in it.

We controlled demographic variables that may act as a potential confounder. The differences between males and females in terms of neuropsychological functioning have been documented [14]. Age-related diseases accelerate the rate of neuronal dysfunction, neuronal loss, and cognitive decline [15]. The cognitive function also depends on education level in the direction that having more education was associated with better cognitive function [16, 17]. The study about significant trends of increasing mean cognitive performance with increasing income exists [17]. In addition, employment status and marital status are associated with cognitive performance [18, 19], and life time smokers tend to experience the cognitive decline larger with increasing number of pack-years smoked [20]. We, therefore, controlled these variables in statistical analysis, even though they are not the interest of our analysis.

Leisure activities had a protective effect against MCI in our study and this finding was consistent with other studies [3, 21, 22]. A cohort study conducted in China suggested that leisure activities in old age may protect against cognitive decline for both women and men, and different types of activities seem to benefit different cognitive domains [23]. Mental activity was associated with global cognition, language, and executive function; physical activity was associated with memory and language; and social activity was associated with global cognition [23]. Although the mechanism of these findings is not yet clear, there are some proposed hypothesis. Cognitive reserve is the most relevant mechanism which is based on more efficient utilization of brain networks or of enhanced ability to recruit alternate brain networks as needed [24]. According to this hypothesis, life experience may influence neural processing and synaptic organization by permitting neurological processes to become more efficient, adaptive, and plastic, thus allowing some people withstand progressing cognitive decline better than others. Leisure activities may also have beneficial effects through psychological and behavioral pathways by lowering stress, having a better diet, and healthier lifestyle, reducing the risk of worse cognitive function [25]. Active individuals are more likely to engage with others, leading to positive emotional states and lower stress [26].

Present study found that alcohol drinking frequency is associated with MCI. There is an ongoing debate about the effect moderate alcohol drinking and the cognitive function. Some studies reported that the cognitive function decreased with alcohol drinking [27], while other studies reported that moderate alcohol drinking improved the cognitive function [28, 29]. One longitudinal prospective study insists that light alcohol consumption does not protect cognitive function [27]. The results from this study indicated that the observed benefits of moderate alcohol intake for cognitive function reported by others might occur due to a control group which is biased towards poor health, because people who have poor health tend to quit drinking alcohol. In contrary, a cohort study suggests that J-shaped relationship may exist between alcohol consumption and cognitive impairment [28]. That is, the cognitive functions of both heavy drinkers and abstainers decreased to a significantly greater degree during follow up than that of patients who consumed light-moderate alcohol. Our findings of insignificant OR for MCI by 2-5times/month alcohol drinking frequency corresponding to moderate alcohol consumption might be thought of as the reason that dose-response relationship between alcohol drinking and cognitive function is not yet clear like above (Table 3).

Interestingly, under the crude model, MCI prevalence decreased with increasing alcohol drinking frequency while; however, after adjusting for all covariates, the prevalence increased with increasing alcohol drinking frequency (Table 3). The proportion of ≥6times/month alcohol drinking frequency by age decreased from 28.7% to 25.3% and 16.0% at age 40-49 years, 50-59 years, and ≥60 years, respectively (Table 1). In addition, the proportion of MCI cases by alcohol drinking frequency decreased from 23.9% to 19.0%, 15.5%, and 16.1% at alcohol drinking frequency never, ≤1time/month, 2-5times/month, and ≥6times/month, respectively. Due to this evidence, in the crude model, the majority of older people belong to groups with a low frequency of alcohol drinking, so it can be assumed that the lower the frequency of alcohol drinking, the higher the MCI prevalence.

This study has several strengths. First, this is the first study to investigate the interaction of leisure activity and alcohol drinking on MCI in the Korean population. There is evidence that alcohol use was higher among individuals who spent more time involved in athletics and socializing [30]. Therefore, we investigated the interaction of these variables. Second, we focused on MCI, unlike most prior studies that investigated Alzheimer disease or dementia among cognition-related disease [5, 7]. Patients with MCI are at higher risk for developing Alzheimer disease with an estimated conversion of 10 to 15% per year [31]. Luis et al emphasized the need for uniformity in the use of instruments in epidemiologic studies to establish population estimates for diverse ethnic and cultural groups [32]. Finally, the 2019 KCHS data used in this study represent the general population in Korea; therefore, the above results can be generalized to the Korean population.

Nevertheless, the limitations of the present study should be considered. First, KCHS is a cross-sectional study so that we cannot draw inference for the causality between leisure activity, alcohol drinking and MCI. It would be necessary to use cohort or panel data to investigate the causal relationships between these variables in the future. However, given the benefits of leisure activity on health and the side-effects of alcohol drinking, it is hard to deduce a reverse relation logically. Secondly, MCI status was measured by relying on not a specialist’s diagnosis but the participants’ subjective answers, which is likely to lead to bias. Finally, there are some factors that affect cognitive function but could not be controlled in our study. Type 2 diabetes mellitus is an important risk factor for Alzheimer disease and dementia with interaction of other factors such as hypertension and dyslipidemia [33]. However, we could not use this variable because there is no division between type 1 and 2 diabetes in our database. There might also be cases where cognitive function was improved by medicine despite poor actual cognitive function. For these reasons, the MCI status may have been overestimated or underestimated. Follow up studies on MCI should consider the effects of these factors.

In conclusion, this study presented the evidence that engaging leisure activity is associated with increased cognitive function while higher alcohol drinking frequency decreased it. In addition, we observed the joint effects of leisure activity and alcohol drinking on mild cognitive impairment (MCI) when exposed simultaneously. The tendency of interaction on additive scale and multiplicative scale was the same, while only the latter was statistically significant. These results suggested that further studies need to investigate the interactions of leisure activity and alcohol drinking on cognitive function with cohort population.