The characteristics of the study population are presented in Table 2. Approximately 45.7% of the participants were men and 54.3% were women. The prevalence of overweight and obesity in men was 21.7% and 2.9%, respectively, that in women was 19.6% and 4.4%, respectively. BMI distribution were statistically different between different age groups (P < 0.001), people aged 60–69 years showed higher prevalence of overweight and obesity (37.9%) than other groups. A higher percentage of older population with high household annual income reported overweight or obese (P < 0.001). The elderly with 0–5 years of schooling reported obviously lower percentage of overweight. The divorced showed higher percentage of overweight but none of them were obese, the separated reported higher percentage of obesity (4.6%). The prevalence of overweight and obesity in the elderly living in city (31.2%) was much higher than that of those who living in town (22.0%) and rural areas (21.9%). People whose staple food was wheat (noodles, bread, etc.) reported higher prevalence of overweight and obesity (29.4%) than others, while only 21.0% of people who ate rice as their staple food reported overweight or obesity. Non-smoker and non-drinker reported higher rates of obesity (P < 0.01). Obesity accounted for a higher proportion of people who exercised (P < 0.001).
Table 2
Descriptive statistics of study population
Variable
|
n
|
Underweight (%)
|
Normal
(%)
|
Overweight
(%)
|
Obesity
(%)
|
p value
|
Gender
|
|
|
|
|
|
|
Male
|
4362
|
12.3
|
63.0
|
21.7
|
2.9
|
<0.001
|
Female
|
5189
|
17.9
|
58.1
|
19.6
|
4.4
|
Age
|
|
|
|
|
|
|
60-69
|
1299
|
4.2
|
57.8
|
33.4
|
4.5
|
<0.001
|
70-79
|
2608
|
8.0
|
58.9
|
28.1
|
5.1
|
≥80
|
5644
|
21.3
|
61.6
|
14.1
|
2.9
|
Household annual income (yuan)
|
|
|
<13680
|
3184
|
16.4
|
61.5
|
18.4
|
3.7
|
<0.001
|
13681 - 60000
|
3537
|
16.8
|
60.0
|
19.7
|
3.5
|
>60000
|
2830
|
12.4
|
59.5
|
24.0
|
4.1
|
Years of schooling
|
|
|
|
0-5
|
6535
|
18.4
|
60.6
|
17.6
|
3.4
|
<0.001
|
6-10
|
2189
|
9.3
|
59.3
|
27.0
|
4.4
|
11-15
|
656
|
6.9
|
61.1
|
27.4
|
4.6
|
>15
|
171
|
9.9
|
61.4
|
25.7
|
2.9
|
Marital status
|
|
|
|
|
|
|
Married and living with spouse
|
4338
|
8.9
|
60.8
|
26.2
|
4.1
|
<0.001
|
Separated
|
174
|
17.2
|
60.3
|
17.8
|
4.6
|
Divorced
|
28
|
17.9
|
57.1
|
25.0
|
0.0
|
Widowed
|
4941
|
21.0
|
59.8
|
15.8
|
3.4
|
Never married
|
70
|
11.4
|
70.0
|
15.7
|
2.9
|
Current residential area
|
|
|
|
|
City
|
2393
|
10.4
|
58.3
|
26.0
|
5.2
|
<0.001
|
Town
|
3138
|
17.2
|
60.8
|
18.8
|
3.2
|
Rural area
|
4020
|
16.8
|
61.2
|
18.7
|
3.2
|
Staple food
|
|
|
|
|
|
|
Rice
|
5720
|
17.4
|
61.6
|
18.0
|
3.0
|
<0.001
|
Corn (maize)
|
398
|
16.1
|
54.8
|
23.6
|
5.5
|
Wheat (noodles, bread, etc.)
|
1573
|
9.9
|
60.8
|
24.6
|
4.8
|
Rice and wheat
|
1791
|
13.1
|
58.0
|
24.3
|
4.6
|
Other
|
69
|
29.0
|
40.6
|
26.1
|
4.3
|
Smoking
|
|
|
|
|
|
|
Smoker
|
1533
|
15.8
|
64.6
|
17.9
|
1.7
|
<0.001
|
Non-smoker
|
8018
|
15.3
|
59.6
|
21.1
|
4.1
|
Alcohol drinking
|
|
|
|
|
|
|
Drinker
|
1471
|
12.8
|
62.8
|
21.8
|
2.5
|
<0.01
|
Non-drinker
|
8080
|
15.8
|
59.9
|
20.3
|
3.9
|
Physical activity
|
|
|
|
|
|
|
Yes
|
3349
|
10.6
|
59.3
|
25.9
|
4.2
|
<0.001
|
No
|
6202
|
17.9
|
60.9
|
17.7
|
3.5
|
Generalized trust (people around are not trustworthy)
|
|
|
Very great or great extent
|
1499
|
15.1
|
57.3
|
22.9
|
4.6
|
<0.05
|
Medium
|
1094
|
14.5
|
62.7
|
19.1
|
3.7
|
Very small or small extent
|
6958
|
15.5
|
60.6
|
20.3
|
3.5
|
Interaction with friends
|
|
|
|
|
|
|
Yes
|
5833
|
12.2
|
61.2
|
23.0
|
3.7
|
<0.001
|
No
|
3718
|
20.4
|
59.1
|
16.8
|
3.7
|
Participation of organized social activities
|
|
|
|
|
Yes
|
1510
|
7.7
|
58.5
|
29.4
|
4.3
|
<0.001
|
No
|
8041
|
16.8
|
60.7
|
18.9
|
3.6
|
A majority of respondents had some trust in people around them, about 15.7% of the participants reported people around them were not trustworthy to very great or great extent, more than one-third of the elderly had no interaction with friends, and about 84.2% of the elderly had never participated in organized social activities.
Ordinal logistic regressions on BMI as a dependent variable were carried out (Table 3). Models 1–3 examine the association between each component of social capital and BMI after controlling for sociodemographic, socioeconomic characteristics and some influencing health behaviours by putting each component of social capital into the model one by one: no confounder was controlled in Model 1, gender, age, years of schooling, marital status, residence area, and household annual income were controlled in Model 2, and Model 3 examines the association between all components of social capital and BMI with adjustment for staple food, smoke, alcohol drink, and physical activity in addition to the confounders in Model 2.
Table 3
Odds ratios (95% confidence Intervals) for respondents reporting obesity
|
Model 1 (Crude OR)
|
Model 2a
|
Model 3b
|
Generalized trust (people around are not trustworthy)
|
|
|
Very great or great extent
|
1.137* (1.027–1.246)
|
1.111 (0.995–1.226)
|
1.117*(1.006–1.229)
|
Moderately
|
0.993 (0.868–1.118)
|
0.960 (0.832–1.087)
|
0.994 (0.867–1.121)
|
Very small or small extent
|
1.00
|
1.00
|
|
Interaction with friends
|
|
|
|
Yes
|
1.451***(1.366–1.535)
|
1.232*** (1.146–1.319)
|
1.240***(1.152–1.328)
|
No
|
1.00
|
1.00
|
|
Participation of organized social activities
|
|
|
Yes
|
1.670***(1.561–1.780)
|
1.196**(1.078–1.314)
|
1.182**(1.062–1.301)
|
No
|
1.00
|
|
1.00
|
*p < 0.05; **p < 0.01; ***p < 0.001; Results are from proportional odds models. Results are displayed as ORs of change in BMI status (contrasting increase vs constant high/low or decrease; or increase or constant high/low vs decrease) per unit increase in the original scale of generalized trust, interaction with friends or in participation of organized social activities. ORs > 1 indicate a positive change in the outcome as a response to an improvement of exposure. |
a Adjusted for gender, age, years of schooling, marital status, residence area, and household annual income. |
b Adjusted for gender, age, years of schooling, marital status, residence area, household annual income, staple food, smoking, alcohol drinking, and physical activity. |
The elderly who did not trust people around them had greater odds of being obese at Model 1 [Odds Ratio (OR) 1.137, 95% Confidence Interval (95% CI) 1.027 to 1.246]. After adjusting for confounders (gender, age, years of schooling, marital status, residence area, household annual income, staple food, smoking, alcohol drinking, and physical activity), a slightly lower odds were observed in Model 3 [Adjusted Odds Ratio (AOR) 1.117, 95% CI 1.006 to 1.229].
Among the interaction with friends categories, the elderly interacting with friends (OR 1.451, 95% CI 1.366 to 1.535) registered considerably higher BMI compared to those who did not at Model 1, and slightly lower odds were observed in Model 3 (AOR 1.240, 95% CI 1.152 to 1.328).
And significant association between participation of organized social activities and obesity was found, the group who participated organized social activities 67.0% higher odds of being obese (OR 1.670, 95% CI 1.561 to 1.780), and the AOR was decreased slightly after controlling for all potential confounders (AOR 1.182, 95% CI 1.062 to 1.301).
In summary, those with lower generalized trust and social participation showed higher BMI, i.e. obesity when gender, age, years of schooling, marital status, residence area, household annual income, staple food, smoking, alcohol drinking, and physical activity were taken into account.