Byline: Jagan. Pillai, Joe. Verghese
Interest in the role of social networks as a protective factor in the development of dementia over the last decade has increased with a number of longitudinal studies being published on the possible association of different lifestyles with dementia. This review examines and provides a summary of the published longitudinal studies exploring the effect of social network on dementia, with particular focus on their relevance to the Indian society. Potential cognitive and biological mechanisms mediating the effects of social networks on dementia are discussed. Results from observational studies suggest that degree of social engagement, marriage, living with someone and avoiding loneliness may have a protective effect on developing dementia that could be applicable to both Indian and western societies. A deeper analysis of the nature of social networks and dementia pertinent to Indian society is awaited.
Increasing life spans of populations worldwide has been accompanied by an increasing prevalence of age related diseases such as dementia. Around 25 million people worldwide have dementia, and the number of people with dementia is predicted to exceed 80 million by 2040.[sup]  This vast dementia burden lends a new urgency towards identifying effective preventive strategies. Social support is an important determinant of healthy aging.[sup] , Social isolation and an unengaged lifestyle have been reported to be associated with accelerated cognitive decline with aging.[sup] , The role of social environment as a risk factor for dementia has received increasing attention over the last decade.[sup]  This review examines published observational studies in this field with particular focus on their relevance for the Indian society.
Healthy aging in India
In an Indian context, the joint family is often invoked as a keystone in social support and healthy aging. However, this social support system has been changing over the past few decades. Many social and demographic explanations have been proposed for changes in the traditional support systems for older adults in India. Changes in social customs in urban Indian society in recent years, the expected doubling of the elderly population by the year 2021, decrease in the number of young caregivers by declining birth rates and the out migration of children of aged parents from villages to towns and cities, and the break up of the traditional Indian joint family structure combined with the low educational and economical status of many of the elderly in the rural areas have been invoked as barriers to healthy aging in India.[sup] , The focus on the joint family structure in Indian aging studies is sometimes thought to be overemphasized with a dearth of investigations towards other possible mechanisms.[sup]  The role of social networks and dementia in the Indian context is therefore unclear and worthy of study. The studies being reviewed here have opened up a highly relevant question; Are some social structures more protective than others towards development of dementia and preserving cognitive function in late life? An answer to this question could have an impact on the future decisions on social and health policy of the Indian subcontinent, home to more people than Africa and South America combined.
Social Networks Defined
The nature of the social environment be it culture, institutions, families, groups with shared interest and/or proximity are thought to be captured by the number, frequency, and degree of interactions with other people. The term social network has been used to capture these interactions. It is defined as 'the actual set of links of all kinds among a set of individuals'.[sup]  It functions as a set of relations which persons use to achieve their ends.[sup]  There are two approaches to the study of social networks, as the total network, such as the total number of interactions between students in a classroom [Figure 1] or as the network radiating from a single person, 'personal social network' [Figure 2]. …