Prevalence and Correlates of Vision Impairment and Its Association With Cognitive Impairment Among Older Adults in India: An Epidemiological Study

Abstract

Background

Like other major chronic diseases, vision impairment is an independently associated risk factor of cognitive decline among older individuals. We in this study, aim to investigate what are the predictors of vision impairment in old age and how impaired vision is associated with cognitive impairment among the aging population.

Methods

The present research used data from Building a Knowledge Base on Population Aging in India. The effective sample size for the present study was 9541 older adults. Descriptive statistics and bivariate analysis was used to find the preliminary results. Further, binary logistic regression analysis was been done to fulfil the objective of the study.

Results

About 6 in every 10 older adults had a problem of vision impairment. Further, nearly 60% of older adults had cognitive impairment in India. Diabetes [OR: 1.55, CI: 1.32-1.81], hypertension [OR: 1.60, CI: 1.42-1.80], heart disease [OR: 1.43, CI: 1.16-1.76] and cataract [OR: 5.97, CI: 4.83-7.38] were the risk factors for vision impairment among older adults. It was revealed that the older adults who had vision impairment were 11% significantly more likely to have cognitive impairment when compared with the older adults who do not suffer from vision impairment [OR: 1.11, CI: 1.01-1.23]. Low psychological health [OR: 1.55; CI: 1.36, 1.77], low ADL [OR: 1.80; CI: 1.43, 2.27], low IADL [OR: 1.26; CI: 1.14, 1.40], poor self-rated health [OR: 1.28; CI: 1.15-1.41] and chronic morbidity [OR: 1.27; CI: 1.14, 1.41] were the significant factors for cognitive impairment among older adults in India

Conclusions

Additional efforts in terms of advocacy, availability, affordability, and accessibility especially in a country with a greater illiteracy rate are mandatory to increase the reach of eye-care services and reduce the prevalence of avoidable visual impairment and vision losses that lead to cognitive deficits among the older population.

Background

Cognitive deficit in an aging population is becoming a global concern for health and social policy (H. L. Park, O’Connell, & Thomson, 2003). With advancing age, the incidence of sensory and intellectual loss increases affecting the cognitive functioning among older individuals (Fischer et al., 2016). Globally, the prevalence of moderate to severe vision impairment in older adults has been reported as highest in South Asia (Stevens et al., 2013).

It is shown that the public health burden due to vision impairment is substantial and comparable to that of other major diseases in assessing the health-related quality of life (S. J. Park, Ahn, & Park, 2016). A recent study found that there has been no significant reduction in the amount of preventable visual impairment cases over the last decade (Adelson et al., 2020). A review of clinical and epidemiological studies on causes of vision loss found a strong independent association of hypertension with several eye conditions that ultimately result in visual impairment (Bhargava, Ikram, & Wong, 2012). Further, evidence from population-based studies suggests that a large proportion of vision impairments are attributable to diabetic retinopathy during the first 2 decades of developing diabetes (Chou et al., 2010; Fong et al., 2004). A study based on Global Burden of Disease and available population-based studies worldwide indicate that in 2010, more than 40 percent of blindness and 20 percent of visual impairments in South Asia are caused by cataracts (Khairallah et al., 2015). Other chronic health conditions such as heart disease, stroke, and depression were more likely to be reported by people with vision impairment than those without and were associated with self-rating of poor health status (Crews, Chou, Sekar, & Saaddine, 2017).

A growing body of literature based on cross-sectional and longitudinal datasets have shown that vision impairment is associated with cognitive decline among the older population (Anstey, Luszcz, & Sanchez, 2001; Davidson & Guthrie, 2019; Spierer, Fischer, Barak, & Belkin, 2016; Woo et al., 2012). Changes in multiple measures of vision such as visual acuity, sensitivity, and visual processing speed have been observed among the aging population, and these changes have been associated with cognitive impairments (Munoz, Stawski, Sliwinski, Smyth, & Macdonald, 2018; Whitson et al., 2018). On the other hand, some studies found no significant association between vision loss and cognitive impairment among older adults (Duron & Hanon, 2008). Thus, whether a visual impairment is accompanied by a decline in cognitive ability remains uncertain. However, a significant association has been found and well-documented between visual impairment and dementia (Davies-Kershaw et al., 2018; Dawes, Wolski, Himmelsbach, Regan, & Leroi, 2019; Lawrence, Murray, Ffytche, & Banerjee, 2009; Luo et al., 2018). Additionally, a wealth of epidemiological studies have indicated that people with age-related eye diseases have a reduced cognitive score compared to those with healthy eyes (Baker et al., 2009; Harrabi et al., 2015; Ong et al., 2012; Woo et al., 2012).

Due to its increased prevalence and greater effect on physical and mental health, cognitive impairment deserves special attention among all chronic conditions. However, unlike other major chronic diseases, vision impairment as an independently associated risk factor of cognitive decline among older individuals is often overlooked by investigators and policymakers. Thus, we aim to investigate what are the predictors of vision impairment in old age and how impaired vision is associated with cognitive impairment among Indian older adults.

Data And Methods

Results

Table 1 represents the socio-demographic profile of older adults. It was revealed that about 10% of older adults suffered from diabetes while the older adults who suffered from hypertension were about 21%. Almost 1% of older adults suffered from a stroke while only 6% of older adults suffered from heart diseases. About 13% of the older adults had cataracts. Nearly 23% of older adults had low psychological health. Older adults with low Activities of Daily Living (ADL) and Instrumental Activities of Daily Living (IADL) were nearly 7% and 57% respectively. Nearly 55% of older adults had poor self-rated health (SRH). About 65% of older adults suffered from one or more chronic diseases. Nearly 39% of older adults were not in a union as per marital status. About 51% of older adults had no education while 67% of older adults were currently not working. Almost 6% of older adults were living alone and about 21% of older adults had no community involvement. Nearly 17% of older adults had no trust over someone.

Table 2 gives an insight into the distribution and logistic regression estimates of older adults having vision disability by their background characteristics. It was found that the odds of vision impairment were significantly high among older adults with diabetes in comparison to older adults who do not have diabetes [OR: 1.55, CI: 1.32–1.81]. Older adults with hypertension were 60% significantly more like to have vision impairment in comparison to the older adults who do not suffer from hypertension [OR: 1.60, CI: 1.42–1.80]. Older adults who suffered from stroke were 6% less likely to have visual impairments in comparison to the older adults who have not suffered from stroke [OR: 0.94, CI: 0.57–1.57]. The odds of vision impairment were significantly high among older adults with heart disease in comparison to older adults who do not have heart disease[OR: 1.43, CI: 1.16–1.76]. Older adults with cataracts were almost six times significantly more like to have vision impairment in comparison to those who do not have cataract [OR: 5.97, CI: 4.83–7.38]. Older adults in the age group 80 + were almost 2.4 times significantly more likely to have vision impairment [OR: 2.41, CI: 2.02–2.88] while older adults among the age group 70–79 were 66% significantly more likely to have vision impairment compared to the 60–69 years age group [OR: 1.66, CI: 1.49–1.85]. The odds of vision impairment was significantly low among the older adults who were currently in the marital union as per marital status [OR: 0.88, CI: 0.79–0.99]. Older adults who had living arrangements as co resided were 13% significantly less likely to suffer from vision impairment compared to those who lived alone [OR: 0.77, CI: 0.63–0.95]. The odds of vision impairment was significantly high among older adults from the rich wealth quintile as compared to older adults from the poor wealth quintile [OR: 1.18, CI: 1.03–1.36].

Table 3 is a representation of the distribution and logistic regression of older adults having cognitive impairment. It revealed that the older adults who had vision impairment were 11% significantly more likely to have cognitive impairment when compared with the older adults who do not suffer from vision impairment [OR: 1.11, CI: 1.01–1.23]. The odds of cognitive impairment were significantly high among older adults with low psychological health issues [OR: 1.55, CI: 1.36–1.77]. The older adults with low ADL and IADL were 80% and 26% significantly more likely to have cognitive impairment respectively in comparison to older adults with high ADL and IADL [OR: 1.80, CI: 1.43–2.27], [OR: 1.26, CI: 1.14–1.40]. The odds of cognitive impairment among older adults with poor self-rated health (SRH) was significantly high [OR: 1.28, CI: 1.15–1.41]. The older adults with chronic morbidity were 27% significantly more likely to have cognitive impairment compared to older adults who do not have chronic morbidity [OR: 1.27, CI: 1.14–1.41]. The older adults who were currently in a union as per marital status were 9% less likely to have cognitive impairment. The odds of cognitive impairment among older adults who had living arrangements as co resided was high [OR: 1.01, CI: 0.81–1.25] while among older adults who had community involvement was significantly low [OR: 0.79, CI: 0.69–0.9]. The older adults who had trust over someone were 22% significantly less likely to have cognitive impairment in comparison to the older adults who do not have trust over someone [OR: 0.78, CI: 0.68–0.89].

Discussion

A higher prevalence of chronic conditions such as diabetes, hypertension, and heart disease consistent with past studies, is strongly associated with vision impairment among older people (Crews et al., 2017). Consistently, the present study found that vision impairment is significant associated with reporting diabetes among older individuals. Again, studies have found patients with diabetes militias to be at an increased risk of developing vascular dementia and Alzheimer’s disease (Arvanitakis, Wilson, Bienias, Evans, & Bennett, 2004; Exalto, Whitmer, Kappele, & Biessels, 2012; Peila, Rodriguez, & Launer, 2002). Hence, establishing a link that relates diabetes and vision impairment with cognitive functioning is required that may allow more effective screening for and prevention of vision impairment and/or cognitive decline to be developed in the future.

Vision impairment as a post-stroke disability has been well-acknowledged in the literature (Sand et al., 2013, 2016). Concordant with past studies that have shown that people who experienced a stroke were at higher risk of visual defects than people without experiencing stroke (Suchoff et al., 2008), results of the present study showed that stroke is significantly associated with visual impairment among older adults. Further, clinical studies found that high blood pressure increases the risk of developing diabetic retinopathy and other retinal vascular diseases (Duke-Elder, 2007; Wong et al., 2001). In line with this, we found a significant association of hypertension with vision impairment among the study participants. Moreover, multiple studies have found that compared with older adults who have normal vision, visually impaired persons had higher chances to have heart diseases and cardiovascular mortality (Dianed Zheng et al., 2012; Evans et al., 2002; Hsueh et al., 2019; Liew, Wong, Mitchell, Cheung, & Wang, 2009). Similarly, the present study found a significant positive association of heart disease with reporting visual impairment in the older participants.

Cataracts are found to be the leading cause of blindness and visual impairment worldwide, especially in developing countries (Bourne et al., 2013). A meta-analysis of all available population-based studies found that the highest percentages of visual impairment caused by cataracts were recorded in the South Asian region (Khairallah et al., 2015). The present analysis also shows that after controlling for socio-demographic variables, the chances of reporting vision impairment among older adults who had cataracts were almost six times higher than their counterparts. Although cataracts and resultant impairment cases can be avoided with early detection and timely intervention, the delivery of surgical interventions continues to be a challenge in developing countries (Khanna, Pujari, & Sangwan, 2011).

On the other hand, vision impairment among aging populations is closely associated with their cognitive and behavioral manifestations (Clemons, Rankin, & McBee, 2006). Consistently, our results suggested a significant relationship between visual and cognitive impairment, an association not previously demonstrated in any population-based studies in India. Findings from several cross-sectional and longitudinal studies in other countries, however, support such an association (Anstey et al., 2001; Davies-Kershaw et al., 2018; Luo et al., 2018; Mandas et al., 2014). Another Japanese study found that older adults with both impaired vision and hearing had higher odds of cognitive impairment (Mitoku, Masaki, Ogata, & Okamoto, 2016). Further, such studies suggested that better visual acuity by means of cataract surgery or refractive correction and wearing glasses seem to correlate with better cognitive functioning (Albers et al., 2015; Rogers & Langa, 2010; Spierer et al., 2016; Tamura et al., 2004). Contrarily, some of them found that vision-enhancing interventions did not lead to short-term improvements in functioning or cognitive status (Elliott, McGwin, & Owsley, 2009).

While the strength of this study is that it uses data from a large, nationally representative, population-based survey to examine a comprehensive list of chronic conditions in conjunction with vision impairment and its association with a cognitive deficit, it is subject to several limitations. First, the data is cross-sectional in nature; we, therefore, cannot confirm whether a cognitive decline preceded vision impairment or vision impairment preceded a cognitive deficit, and we cannot infer causality between chronic illnesses and vision impairment. Second, the data excludes people living in nursing homes and other institutional settings, who may report higher rates of vision impairment. Third, the vision question in BKPAI is a self-reported measure of function and does not capture the severity of vision problems or different eye diseases.

Conclusion

The results underscore the risk of vision impairment in older ages as a public health burden compared with other major chronic diseases and the importance of normal vision for healthy brain aging. Additional efforts in terms of advocacy, availability, affordability, and accessibility especially in a country with a greater illiteracy rate are mandatory to increase the reach of eye-care services and reduce the prevalence of avoidable visual impairment and vision losses that lead to cognitive deficits among the older population.

Research and programs must consider the strategies to include people with both vision and cognitive impairment along with chronic illnesses in efforts to reduce the burden of aging and chronic conditions. Further, other causes of visual impairments should be explored using longitudinal studies and the clinical investigation is warranted to understand the underlying pathophysiology linking visual impairment and cognitive decline in aging populations.

Abbreviations

Declarations

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Tables

Table-2 Percentage distribution of older adults having vision disability by their background characteristics among older adults

Table-3 Percentage distribution of older adults having cognitive impairment by their background characteristics among older adults