[Protective effects of social networks on disability among older adults in Madrid and Barcelona, Spain, in 2005].

Background: The loss of autonomy at advanced ages is not only associated with ageing, but also with the characteristics of the physical and social environment. Recent investigations have shown that social networks, social engagement and participation act like predictors of disability among the elderly. To analyze the effect of social networks on the level of autonomy (instrumental and basic disability) at initial stages of the old age.

Methods: The source of data is the first wave of the survey 'Processes of Vulnerability among Spanish Elderly', carried out in 2005 to a sample of 1,250 individuals? with the later purification of the data, it was in a size final sample of 1.244 individuals? The population object of study is the cohort aged 70 to 74 years in metropolitan areas (Madrid and Barcelona) and not institutionalized. Disability is measured by the development of basic activities of daily life (ADL), and instrumental activities of daily life (IADL). The structural aspects of the social relationships are measured through the diversity of social networks and participation, for which a global indicator of social network diversity was built.

Results: For each unit that diminishes the indicator of social network diversity, the probability of suffering an instrumental disability? in front of not suffering any disability? is multiplied by 0.97 (IC95% 0.95 - 0.99), and the probability of suffering a basic disability is multiplied by 0.91 (IC95% 0.87 - 0.94).

Discussion: Like in other geographic scopes, a statistically significant relationship exists between the indicator of diversity of social network used and the disability, in its two levels of graveness. Therefore, the diversity of the social network seems to show a protective effect in front of the disability among the Spanish urban population at the beginning of the age.