The Senior Neighborhood Quality of Life Study was an observational study of ambulatory adults 66
years of age or older in 2 major US metropolitan regions selected to vary in neighborhood income and walkability conducted in 2005–2008. Study methods have been described elsewhere [15
]. The study was approved by appropriate institutional review boards.
896) completed two surveys and wore an accelerometer for 7
days. For these analyses, demographic data, self-rated health, and physical functioning were taken from survey one, physical activity location from survey two (conducted 6
months later). Five questions developed by investigators assessed physical activity location: a) indoors at home or apartment building, b) other indoor settings like recreation facilities, c) outdoors in a green or open space, d) outdoors in local streets or neighborhood, and e) outdoors outside of local neighborhood. Response options were: “more than once a week”, “once a week”, “less than once a week”, and “hardly ever”. The response categories were collapsed to those who were active in the location at least once a week versus less often, and four discrete groups were constructed: those who were infrequently active
(i.e., less than once a week or hardly ever across all 5 questions), those who were physically active at least once a week indoors only
, those who were physically active at least once a week outdoors only
, and those who were physically active both indoors and outdoors
at least once a week. These groups were chosen to control for the number of locations and isolate indoor and outdoor effects.
Self-rated health was measured by the question “In general, how would you say your health is, on a scale of 1–5, excellent to poor?” from the 12-item short-form health survey [16
]. The scoring was reversed for these analyses so higher scores indicated better quality of life. Mobility impairment was assessed using the validated 11-item advanced lower-extremity subscale of the Late-Life Function and Disability Instrument [17
], which assesses a broad range of functional capabilities requiring lower-body function (e.g., walking several blocks, going up and down 3 flights of stairs, getting up from the floor).
Ambulatory assessment of moderate-to-vigorous physical activity (MVPA) was accomplished using the extensively validated Actigraph accelerometer (Actigraph, LLC; Fort Walton Beach, FL, model 7164 or 71256) [18
]. Participants were instructed to wear the device for 7
days. Data were collected in 1-minute epochs and cleaned and scored using MeterPlus version 4.0 software (Santech, Inc.; www.meterplussoftware.com
). Scoring of MVPA was based on a commonly used cut-point (≥1952 counts/minute), [19
] and derived as average minutes of MVPA per valid wearing day. A valid accelerometer hour was defined as having less than 45 consecutive minutes of ‘zero’ counts, and a valid day consisted of at least 8 valid hours.
A mixed model linear regression procedure was employed to adjust for neighborhood clustering effects. Minutes of MVPA per day and self-rated health were the dependent variables. The 4-category activity location was the independent variable. Post hoc pairwise comparisons were run to assess differences across the four groups. Covariates included age, gender, white/nonwhite ethnicity, education (college degree or not), neighborhood walkability and income (high vs. low; included because the study design created variability in these measures; walkability based on individual addresses was not included), and region of the US (Baltimore or Seattle). The model was run with and without physical functioning to assess its role as a mediator since previous studies have indicated low physical functioning may prevent outdoor activity, [12
] and in our own previous analyses physical functioning moderated the relationship between the built environment and walking for transportation [20