Introduction
Nutrition at midlife and beyond influences both health and optimal ageing.1 While there are many ways to define optimal ageing,2 it is commonly described as the maintenance of function across multiple domains (physiological, mental and social).3 Among the factors that can influence optimal ageing is nutrition risk, as low nutrition risk is associated with optimal ageing.4 5 Nutrition risk is the risk of poor nutrition status or nutritional depletion that occurs when food and/or nutrient intake do not meet needs.6 7 Numerous physiological, psychological and social changes or risk factors occur as people age that can result in nutrition risk.8 The consequences of increased nutrition risk include malnutrition, frailty, decreased quality of life, hospitalisation and higher mortality rates.6 9 10 In Canada, approximately one-third of adults aged 50 and older are at nutrition risk.11
Social relationships and social networks also influence optimal ageing.12 Social networks can be defined as ‘the web of social relationships that surround an individual and the characteristics of those ties’.13 Social networks have been shown to influence a number of health outcomes, both physical and psychological.13 Individuals belonging to more diverse network types tend to have better health outcomes, whereas individuals belonging to more restricted networks tend to have worse health outcomes.14–16
Social network characteristics (such as number of social network members, frequency of contact with network members, frequency of social participation) can be used to classify individuals into social network types that range from socially isolated to socially integrated.17 One Canadian study found that adults aged 65 and older belonged to one of six social network types: diverse, friend focused, family-friend, few children, few friends and restricted.17 They also found that social network type was associated with social support.17
Conceptual framework
Our study uses social network theory, as described by Berkman et al, as its conceptual framework.13 This theory describes how social networks affect health outcomes, such as nutrition risk (figure 1). This framework posits that social and cultural contexts (macro level) influence social networks (mezzo level), which in turn affect social and interpersonal behaviour (microlevel). These psychosocial mechanisms (social and interpersonal behaviour) then impact health.13
Characteristics of social networks include their size, range, density, boundedness, proximity, homogeneity and reachability. Characteristics of the ties within these networks include frequency of contact, frequency of participation, reciprocity of ties and duration of ties.13
Social networks affect health outcomes, such as nutrition risk, through psychosocial mechanisms, which include social support, social influence and access to resources and material goods.13 Social networks may influence nutrition risk through several of these psychosocial mechanisms. Eating with others improves dietary intake and reduces nutrition risk.18 Individuals with larger social networks and greater levels of social participation may have more opportunities to eat with others and to have social norms around food reinforced.18 Some studies have found that social support helps reduce nutrition risk, likely because individuals with increased social support have greater assistance with food-related activities, such as meal preparation and grocery shopping.18 Access to resources, in the form of income, has been associated with nutrition risk,19 as individuals with higher incomes have an easier time affording adequate amounts of healthy food.20 However, a few studies have examined the relationship between social network types and nutrition. One study from the UK found that social network type was associated with nutritional status, measured using the Mini Nutritional Assessment-Short Form (MNA-SF).21 Participants who were in, or moving to, more restricted network types had low MNA-SF scores, and thus poor nutritional status.21 A study of frail older adults in South Korea found that social network type was associated with diet quality.22 Participants belonging to more restricted networks had lower diet quality compared with those with larger social networks.22
Currently, it is unknown how social network type affects nutrition risk in Canadian adults at midlife and beyond. If social network types affect nutrition risk, this information can inform programmes and policies designed to reduce the prevalence of nutrition risk and improve nutritional status. It can also help to identify individuals who should be screened proactively for nutrition risk. As nutrition risk occurs before malnutrition, and because it is easier to treat nutrition risk compared with malnutrition, it is important to identify those who should be screened for nutrition risk.23 24
There were two primary objectives of this research, namely: (1) to determine the social network types that Canadian adults aged 45 and older belong to, using the factors at the mezzo level of Berkman et al’s social network theory13 and (2) to discover if social network type is associated with nutrition risk scores and the prevalence of high nutrition risk.