This study examined the proportion of adults aged ≥ 60 years with impaired cognitive function living in three different areas of the Lao PDR, using the Revised Hasegawa Dementia Scale Lao version. The study revealed that cognitive impairment was associated with age, particularly in respondents aged ≥ 65 years, and educational levels. Living in rural areas and in the northern region were associated with higher risk of cognitive impairment in comparison with those living in urban areas or the southern and central regions.
The lower Revised Hasegawa Dementia Scale scores in the current study were partly due to low scores on questions 5 and 6, which involve serial subtraction and counting backwards. Almost all respondents (81.3%) reported having had no formal or primary education. The low level of education among study participants might help explain the difficulties with questions 5 and 6. This study also found lower scores related to remembering words and confrontational naming (questions 7 and 8), and the lowest score was related to word fluency (question 9); these scores may reflect limited educational opportunities during adolescence. Many studies have suggested that having a higher level of education is a protective factor against developing cognitive impairment, indicating that attaining only a low education level is associated with poor cognitive function [15, 31]. Continual mental stimulation gained through learning may increase favourable structural or neurochemical alterations in the brain, thus improving cognitive function . However, several cohort studies have not found associations between low education levels and cognitive decline [33, 34]. Adults aged ≥ 60 years in this study spent their adolescence in the middle of a civil war; therefore, the majority of them did not have any formal education.
Several studies have noted that women are more likely than men to develop cognitive impairment [16, 17]. We found that more women had developed cognitive impairment than men in the bivariate analysis but not in the multivariate analysis. In the Lao PDR, women tend to have a longer life expectancy, and this longer life will be healthier if preventive strategies are undertaken, such as using a multifocal approach to prevent and slow cognitive decline among older adults by encouraging exercise, avoidance of high levels of alcohol consumption, socializing and by preventing NCDs . Additionally, the WHO global action plan on dementia recommends increasing public awareness of and developing programmes to encourage positive attitudes towards dementia in the community . Without a strong health systems response and a formal long-term care sector, those who are disabled at older ages become the responsibility of family caregivers, such as daughters and spouses. Other studies have indicated that older adults who are divorced, separated or widowed have a higher risk of cognitive impairment , but this was observed only in the bivariate analysis in this study.
In the Lao PDR, the high prevalence of harmful alcohol use in adults aged ≥ 18 years  and chronic malnutrition during childhood might affect cognitive function [31, 38]. Risk factors for cognitive impairment include age, family history, education level, brain injury, exposure to pesticides or toxins, and physical inactivity.
Ageing is a risk factor for NCDs such as hypertension  and type 2 diabetes mellitus [26, 27]. In our study, more than one third of respondents had hypertension, and nearly one fifth had type 2 diabetes mellitus. Hypertension and diabetes mellitus account for both small and large vascular changes that can lead to cerebrovascular accidents, strokes, cerebral haemorrhage and micro-cerebral infarcts [39, 40]. Therefore, effective and timely preventive measures or strategies to address the risks of ill health are required. For instance, Japan has invested in primary, secondary and tertiary prevention strategies, especially those addressing hypertension and diabetes, and therefore has both a high life expectancy and a high healthy life expectancy, even among people in older age groups. Japan's health investments were initiated in the 1960s when it was a lower-income country and its population was relatively young. Japan continues to have the highest life expectancy globally, partly due to this early investment and also because people can continue to be active and healthy in their older years.
Although respondents who were overweight or obese were observed to have a lower risk of developing cognitive impairment in this study, many other studies have found that maintaining normal body weight throughout the life span is protective against cognitive impairment [25, 26].
Similar to other studies, respondents who engaged in moderate-intensity physical activity had a lower risk of cognitive impairment [14, 18, 21, 41].
One third of respondents were current smokers and current drinkers. Chronic smokers were more likely to drink alcohol, and smoking tobacco is associated with cognitive decline and neurocognitive diseases in later life . However, this study did not find such an association.
In recent decades, the Lao PDR has transitioned from a low-income country to one that is lower-middle-income. When most households lived in poverty and few people had access to health services, many people died young due to poor nutrition and infectious diseases. Impoverished adults who suffered from poor nutrition and a lack of cognitive stimulation during their early life could perhaps be at risk of cognitive impairment. As poverty declined and health services improved in the Lao PDR, there was a rapid reduction in deaths caused by diseases such as malaria, tuberculosis and diarrhoea, with corresponding increases in life expectancy. However, infants may still be malnourished, and children may still not receive an education , both of which may impact development at an early stage and place them at risk of cognitive impairment in later life. In addition, unhealthy lifestyles in adult life, such as poor diet, smoking, consumption of alcohol and working in stressful occupations, increase the risks of NCDs such as obesity, diabetes, vascular diseases and hypertension, all of which are associated with cognitive impairment later in life [40, 41].
A limitation of this cross-sectional study is that it provides only a snapshot in time and does not provide information on cause and effect relationships between cognitive impairment and different risk factors. In addition, the cutoff Revised Hasegawa Dementia Scale score of ≤ 20 may not be appropriate for those unfamiliar with subtraction. Screening for cognitive impairment with the Revised Hasegawa Dementia Scale Lao version might be better if the cutoff was ≤ 18 and if question 5 was removed; the appropriateness of making these changes and using a maximum score of 28 (rather than 30) should be confirmed by comparing these scores with clinical diagnoses in future studies. Future research should be performed not only to detect general cognitive impairment but also to differentiate among specific types of cognitive impairment.
However, this study also has strengths: it was conducted in three different parts of the country and had a large sample of respondents representing urban and rural areas and different sociodemographic features. The study provides evidence for future policy planning in the Lao PDR as increasing numbers of older people will place greater demands on the health services, particularly for the management of chronic NCDs, such as hypertension and diabetes, which can contribute to cognitive decline. Older adults are often likely to have one or more of these conditions and require support from various professionals, such as physiotherapists, dietitians and mental health professionals. WHO and other agencies have long advocated for developing a people-centred, multidisciplinary approach to healthcare. Implementing a robust primary care system requires shifting investments in infrastructure and deploying staff to primary care facilities and health networks, and determining the appropriate technology to be used at all levels of the health system, in keeping with clinical and referral pathways. The critical questions are whether the Lao PDR is ready for such profound changes and what the implications of these changes are for health and social services [5, 42]. To address these questions, it is necessary to understand the public policies and disease prevention strategies that enable healthy ageing in order to focus on the opportunity to plan for universal health coverage in recognition that health systems of the future need to respond to older populations [1, 5] as part of the global commitments to the Sustainable Development Goals .