Table 2.

Description of Potential Explanatory Variables

Concept	Measurement
Married	Being married or with a partner is generally considered a positive factor for mental and physical health and likely provides some buffering from the experience of stress [30]. The variable is coded 1 for if the respondent reported being married or living with a partner and 0 otherwise. The proportion of married individuals increases from the early 20s to the early 30s, levels off through the late 60s and then declines with advancing age (data not shown).
Employment	Employment is a prime candidate variable because of its clear association with age and because major social and activity changes often accompany retirement. In one survey perceived stress was positively associated with unemployment [31]. The variable used here is if a respondent reported being employed fulltime (1), or not (0), including part-time employment, or being out of the work force. Employment rises from the early to late 20s, levels out for the next 24 years until age 52, and then drops quickly thereafter.
Self-rated Health	Health status is another variable that shifts with age and is a reasonable candidate for this inquiry [32], as declining health is usually cited as a central factor yielding the well-being paradox [33]. The Gallup survey included the familiar self-rated health question, and we have dichotomized responses into Excellent, Very Good, and Good (1) versus Fair and Poor (0). There is a linear decline in individuals reporting good health from 87% in the early 20s to about 75% in the early 60s, then a slight rise, followed by a continued decline through 72% in older ages.
Health Problem	Another health-related variable is whether or not a respondent reported a “health problem.” This variable was coded as 1 if a health problem was reported and 0 otherwise. Incidence rises from younger adulthood, though there is a plateau in growth between ages 60 and 75.
Health Insurance	Having health insurance is likely related to age and stress, and recent experimental evidence suggests that having insurance improves well -being [34,35]. A variable was created that is coded 1 for those who report having health insurance and 0 for not having it. Having health insurance increases over the age range and ranges between 70% to over 90% old age
Social Support	Social support has long been known to buffer the effects of stressful environments [36]. The Gallup survey asked if the respondent had family or friends they could count on (coded 1) or not (0), which captures an important component of the construct [37]. This variable has a U-shaped relationship with age with the nadir (about 80%) at 52–55 years and about 10% higher at both ends of the age distribution.
Neighborhood Safety	Studies have shown that perceived safety of one’s neighborhood is related to well-being and stress [38], and the survey asked about feeling safe walking in one’s neighborhood (1) versus not (0). This variable has an inverted-U age-pattern, with perceptions of safety reaching its peak (77%) between ages 48–51, and the lowest levels of perceived safety in old age (60%).
Children at Home	Children living at home and its association with well -being has been a topic previously explored [39], though usually the focus is on middle aged with children living at home versus without children and not on how children might impact the stress-age gradient over the adult lifespan. A variable was constructed that was coded (1) if children were currently living at home versus not (0). This variable has an inverted U-shaped age pattern, with a peak at ages 36–39 (75%) and a decrease through older age (to under 10%). Income has been associated with well-being and stress [40], though in complex ways, in that both variables appear to increase with higher income. A median split on household income (below median (0) vs. above median (1)) was used here, and the age pattern was that of an inverted-U with above median income rates being highest (> 50%) from age 36 through 59.
Religious Belief	Religious beliefs have also been shown to be positively correlated with well - being [41]. The response to a question about how often the respondent attends church, synagogue, or mosque was coded as 1, if attendance was every week or almost every week, and 0 for lower attendance rates. It increased with age from 35% in the youngest to 70% in the oldest participants, with a plateau in the 40s.
Self-reported Medical Diagnoses (7)	The Gallup survey also asked about whether a significant medical diagnosis had ever been given to respondents, including high blood pressure (steady increase over age), high cholesterol (steady increase over age), diabetes (steady increase), depression (inverted U-pattern), heart attack (steady increase), asthma (decline through age 30, then flat with an increase at 56–59, followed by decline), and cancer (steady increase).