Sample characteristics, accelerometer wear time, and accelerometer-assessed sedentary time
Table 1 presents the descriptive statistics of the study sample. A total of 818 older adults were included with a mean age of 74.81 (± 6.19) years. The sample had a higher proportion of women (61.12%) and married or cohabiting persons (65.28%). The proportion of participants with an educational attainment above primary level was considerably higher in Belgian (74.76%) than Hong Kong older adults (46.77%). Physical functioning was generally high with a mean score of 10.2 (± 1.94) out of 12.
Table 1
Sample characteristics and accelerometer wear time
Characteristics
|
ALECS & BEPAS
(n = 818)
|
ALECS
(n = 402)
|
BEPAS
(n = 416)
|
Participant socio-demographics and physical function
|
Age (years; mean ± SD)
|
74.81 ± 6.19
|
75.55 ±6.15
|
74.09 ± 6.15
|
Sex (% female)
|
61.12
|
68.91
|
53.61
|
Education (% above primary school)
|
61.00
|
46.77
|
74.76
|
Marital status (% married or cohabiting)
|
65.28
|
62.94
|
67.55
|
Physical functioning (SPPB score: range 1-12, mean ± SD)
|
10.02 ± 1.94
|
9.94 ± 1.95
|
10.10 ± 1.93
|
Accelerometer-assessed wear time (mean ± SD)
|
Valid weekdays
|
5.16 ± 1.40
|
5.30 ± 1.55
|
5.01 ± 1.24
|
Valid weekend days
|
2.06 ± 0.68
|
2.06 ± 0.74
|
2.07 ± 0.62
|
Average wear time (h/day)
|
13.92 ± 1.46
|
13.53 ± 1.54
|
14.29 ± 1.26
|
Notes. ALECS, Active Lifestyle and the Environment in Chinese Seniors study; BEPAS, Belgian Environmental Physical Activity Study on Seniors study; SD, standard deviation; SPPB, Short Physical Performance Battery
Table 2 shows the average accelerometer-assessed sedentary time and the percentage of wear time spent sedentary by day of the week and time of the day. The percentage of wear time spent sedentary was the lowest early in the morning (6:00 am – 8:59 am), and highest in the evening (6:00 pm – 9:00 pm), both on weekdays (42.7% and 57.7%, respectively) and on weekend days (42.1% and 58.1%, respectively).
Table 2
Average accelerometer-assessed sedentary time and percentage of wear time spent sedentary by day of the week and time of the day
Day of the week
Time of the day
|
ALECS & BEPAS
|
ALECS
|
BEPAS
|
ST (min/h)
|
% of WT
|
ST (min/h)
|
% of WT
|
ST (min/h)
|
% of WT
|
Weekday
|
|
|
|
|
|
|
6:00 am – 8:59 am
|
17.7
(13.0)
|
42.7
|
17.7
(12.3)
|
42.2
|
17.8
(13.9)
|
43.5
|
9:00 am – 11:59 am
|
24.4
(11.7)
|
42.2
|
26.9
(11.7)
|
46.5
|
21.7
(11.0)
|
37.8
|
12:00 pm – 2:59 pm
|
30.00
(11.4)
|
50.8
|
30.9
(11.5)
|
52.8
|
29.0
(11.2)
|
48.6
|
3:00 pm – 5:59 pm
|
28.8
(11.9)
|
49.2
|
29.4
(11.9)
|
51.2
|
28.2
(11.8)
|
47.2
|
6:00 pm – 9:00 pm
|
30.00
(13.75)
|
57.7
|
26.2
(14.8)
|
56.6
|
33.9
(11.3)
|
58.7
|
Weekend day
|
|
|
|
|
|
|
6:00 am – 8:59 am
|
17.0
(12.4)
|
42.1
|
17.1
(11.9)
|
42.3
|
16.9
(13.1)
|
41.8
|
9:00 am – 11:59 am
|
24.6
(11.3)
|
43.0
|
26.2
(11.3)
|
45.9
|
22.8
(11.0)
|
39.8
|
12:00 pm – 2:59 pm
|
30.1
(11.7)
|
50.8
|
31.3
(11.9)
|
53.2
|
28.9
(11.2)
|
48.4
|
3:00 pm – 5:59 pm
|
29.4
(12.1)
|
50.3
|
30.2
(12.3)
|
52.7
|
28.6
(11.8)
|
48.0
|
6:00 pm – 9:00 pm
|
30.6
(13.1)
|
58.1
|
27.2
(14.1)
|
57.1
|
34.1
(10.9)
|
58.7
|
Notes. ALECS, Active Lifestyle and the Environment in Chinese Seniors study; BEPAS, Belgian Environmental Physical Activity Study on Seniors study; ST, sedentary time; WT, wear time
Inter- and intrapersonal variability of older adults’ sedentary time and main effects of socio-demographic factors, physical functioning and study site
Tables 3, 4 and S1 summarize the findings from the LMMs. Most of the variance in accelerometry-assessed sedentary time was due to within-person differences across periods of the day (72.4%) followed by between-person differences within neighborhoods (25.6%) (Table 3; M1). Only 1.3% and 0.7% of the variance were due to between-neighborhood and within-person between-day differences, respectively. Age was positively, and physical functioning negatively, related to sedentary time (Table 3; M2). On average, females and participants from Ghent (Belgium) had lower sedentary time than their counterparts. Socio-demographic characteristics, physical functioning and study site contributed to the explanation of nearly 55% of neighborhood-level variance and 16% of between-person level variance (Table 3; see random parts of M1 and M2). On average, participants tended to accumulate slightly more sedentary time on weekend days compared to weekdays (Table 3; M4). They were more sedentary in the afternoon than morning periods, most sedentary between 6:00 and 9:00 pm and least sedentary between 9:00 am and 11:59 am.
Table 3
Main-effect regression models of sedentary time in older adults
|
Models
|
Correlates
|
M1
|
M2
|
M3
|
Fixed part
|
b
|
95% CI
|
b
|
95% CI
|
b
|
95% CI
|
Wear time (min/h)
|
0.53***
|
0.52, 0.54
|
0.53***
|
0.52, 0.54
|
0.52***
|
0.51, 0.53
|
Age (years)
|
-
|
-
|
0.28***
|
0.21, 0.34
|
0.28***
|
0.21, 0.34
|
Sex (ref: male)
|
|
|
|
|
|
|
Female
|
-
|
-
|
-2.32***
|
-3.17, -1.47
|
-2.30***
|
-3.15, -1.45
|
Education (ref: up to primary school)
|
|
|
|
|
|
|
Above primary school
|
-
|
-
|
0.75
|
-0.10, 1.61
|
0.73
|
-0.12, 1.59
|
Marital status (ref: no partner)
|
|
|
|
|
|
|
Married or cohabiting
|
-
|
-
|
0.27
|
-0.59, 1.12
|
0.25
|
-0.60, 1.11
|
Physical function (SPPB score)
|
-
|
-
|
-0.43***
|
-0.65, -0.21
|
-0.43***
|
-0.65, -0.21
|
Study site (ref: ALECS [Hong Kong, China])
|
|
|
|
|
|
|
BEPAS (Ghent, Belgium)
|
-
|
-
|
-1.57***
|
-2.50, -0.63
|
-1.61***
|
-2.54, -0.67
|
Day of week (ref: weekday)
|
|
|
|
|
|
|
Weekend day
|
-
|
-
|
-
|
-
|
0.24
|
-0.02, 0.51
|
Period of the day (ref: 6:00 am – 8:59 am)
|
|
|
|
|
|
|
9:00 am – 11:59 am
|
-
|
-
|
-
|
-
|
-1.59***
|
-1.97, -1.21
|
12:00 pm – 2:59 pm
|
-
|
-
|
-
|
-
|
3.15***
|
2.76, 3.53
|
3:00 pm – 5:59 pm
|
-
|
-
|
-
|
-
|
2.40***
|
2.02, 2.79
|
6:00 pm – 9:00 pm
|
-
|
-
|
-
|
-
|
6.90***
|
6.54, 7.27
|
Random part
|
Var. comp.
(95% CI)
|
% total var.
|
Var. comp.
(95% CI)
|
% total var.
|
Var. comp.
(95% CI)
|
% total var.
|
Neighborhood-level variance
|
1.66
(0.63, 4.36)
|
1.3%
|
0.75
(0.17, 3.24)
|
0.6%
|
0.77
(0.18, 3.25)
|
0.7%
|
Person-level variance
|
32.41
(29.04, 36.18)
|
25.6%
|
27.38
(24.50, 30.61)
|
22.7%
|
27.24
(24.37, 30.45)
|
24.3%
|
Day-level variance
|
0.91
(0.34, 1.43)
|
0.7%
|
0.91
(0.34, 2.43)
|
0.8%
|
3.17
(2.40, 4.18)
|
2.8%
|
Within-day-level variance
|
91.72
(90.00, 93.47)
|
72.4%
|
91.71
(90.00, 93.46)
|
76.0%
|
81.05
(79.53, 82.60)
|
72.2%
|
LR test
|
χ2(3) = 6452.28; p<.001
|
χ2(6) = 136.21; p<.001
|
χ2(5) = 2681.19; p<.001
|
Type of LR test
|
Random effects
|
Fixed effects: M2 vs. M1
|
Fixed effects: M3 vs. M2
|
Notes. LR, likelihood ratio; var., variance; Var. comp., variance component; ref., reference category; ALECS, Active Lifestyle and the Environment in Chinese Seniors study; BEPAS, Belgian Environmental Physical Activity Study on Seniors study; SPPB, Short Physical Performance Battery; b, regression coefficient; CI, confidence intervals; *** p<.001
Moderating effects of socio-demographic factors, physical functioning and study site in the intrapersonal variability of older adults’ sedentary time
The difference in sedentary time between weekdays and weekend days was similar across study sites, socio-demographic groups and participants with different levels of physical functioning (Table S1). However, the patterns of sedentary time across times of the day differed by sex, educational attainment, age, physical functioning levels and/or study site (Table 4).
Table 4
Interaction effects of time of day on accelerometer-assessed sedentary time
Interaction term
|
χ2(4)
|
p-value
|
Interaction term
|
χ2(4)
|
p-value
|
Two-way interactions
|
|
|
Three-way interactions
|
|
|
Time of day by Age
|
16.70
|
.002
|
Time of day by Age by Study site
|
25.98
|
<.001
|
Time of day by Sex
|
17.99
|
.001
|
Time of day by Sex by Study site
|
36.61
|
<.001
|
Time of day by Education
|
44.64
|
<.001
|
Time of day by Education by Study site
|
31.64
|
<.001
|
Time of day by Marital status
|
4.74
|
.315
|
Time of day by Marital status by Study site
|
7.56
|
.109
|
Time of day by Physical function
|
13.28
|
.010
|
Time of day by Physical function by Study site
|
5.88
|
.208
|
Time of day by Study site
|
455.14
|
<.001
|
|
|
|
Notes. All models with random intercepts at the neighborhood, person and day level, and adjusted for accelerometer wear time, age, sex, educational attainment, marital status, physical function, study site and day of the week; χ2, chi square; results from χ2(4) test because Time of day is a nominal variable with five categories.
In Hong Kong, older adults tended to be the least sedentary early in the morning (6:00 am – 8:59 am), while in Ghent they were the least sedentary between 9:00 am and 11:59 am (Figures 1-3). The difference in sedentary time between late afternoon (3:00 pm – 5:59 pm) and evening (6:00 pm – 9:00 pm) was considerably more pronounced in Ghent than in Hong Kong (Figures 1-3), with older adults from Ghent increasing their sedentary time more than their Hong Kong counterparts in the evening.
In Hong Kong, the difference in sedentary time between age groups was similar across the various periods of the day, with older participants being more sedentary than younger participants (Figure 1 – panel A). In Ghent, no significant difference in sedentary time was observed between age groups early in the morning (6:00 am – 8:59 am) (Figure 1 – panel B). The difference between age groups was significant at other times of the day and the largest between noon and 2:59 pm, with older participants being more sedentary than their younger counterparts.
Hong Kong participants showed larger between-sex differences in sedentary time in the morning than afternoon and evening, with females being less sedentary than males and between-sex differences being the smallest and non-significant in the evening (Figure 2 – panel A). Conversely, while Ghent males and females did not significantly differ in the amount of sedentary time they accrued early in the morning, they differed at other periods of the day whereby females were less sedentary than males (Figure 2 – panel B). The largest between-sex differences were observed in the evening.
In Hong Kong, older adults with lower education attainment were less sedentary than those with higher education in the morning and late afternoon only (3:00 pm – 5:59 pm) (Figure 3 – panel A), while in Ghent a significant difference in sedentary time between educational attainment groups was observed only between 6:00 am and 8:59 am, with the less educated being less sedentary (Figure 3 – panel B).
Finally, the difference in sedentary time between participants with varying levels of physical functioning was the greatest around noon to early afternoon (2:59 pm) followed by the early morning hours (Figure 4). These patterns did not differ across study site.