Table 1.

Variable descriptions of the structural and functional social network characteristics

Variable name	Definition	Unit of measurement (possible range)
Structural characteristics of the social network
Network size	The total number of unique network members mentioned in the questionnaire. Participants with a smaller social network size were considered as more socially isolated.	N (0–40)
Contact frequency
Total contacts per half year	A contact was defined as an interaction between persons. Total contacts (interactions between persons) per half year were computed as follows. We used the highest contact frequency (e.g., daily contact) for every network member as an indicator of the actual contact frequency. Second, we recoded the answer categories of the questionnaire to an estimated number of contacts per half year. For example, “half-yearly” was assumed to comprise one contact, “quarterly” two contacts, “monthly” 6 contacts and “daily or weekly” 48 contacts. Third, we computed the sum of all contacts per half year as the total contact frequency.	N (0–1920)
Percentage of daily-weekly contact	We calculated the percentage of network members that the participant had daily or weekly contact with as the number of daily/weekly contacts divided by network size.	% (0–100)
Proximity
Percentage of network members living within walking distance	We considered geographic proximity as the percentage of all network members who lived within walking distance, calculated as the number of network members living within walking distance divided by network size.	% (0–100)
Type of relationship
Percentage household members	We calculated the percentage of household members as the number of network members living in the same household divided by network size.	% (0–100)
Percentage family members	We calculated the percentage of family members within the network as the number of family members divided by the network size.	% (0–100)
Percentage friends	We calculated the percentage of friends within the network as the number of friends divided by the network size.	% (0–100)
Living alone	Living alone was defined as a person who lived alone in his/ her household.	(yes/no)
Social participation	Social participation was defined as membership in, for instance, a sports club, religious group, volunteer organization, discussion group, self-support group, internet club, or other organization.	(yes/no)
Functional characteristics of the social network
Informational support	Informational support was defined as the number of network members that give advice on problems	N (0–5)
Emotional support (discomfort)	Emotional support related to discomfort was defined as the number of network members that provide emotional support when participants were feeling unwell	N (0–5)
Emotional support (important decisions)	Emotional support related to important decisions was defined as the number of network members that provide the opportunity to discuss important matters	N (0–5)
Practical support (jobs)	Practical support related to jobs was defined as the number of network members that help with small and larger jobs around the house	N (0–5)
Practical support (sickness)	Practical support related to sickness was defined as the number of network members that provide practical help when participants were sick	N (0–5)