Descriptive characteristics
Table 2 summarized the characteristic of participants at baseline by survey period. In the 2008-2011 waves, the prevalence of often loneliness at baseline was 28.2%, which slightly decreased to 25.8% in the 2008-2014 waves. Compared with the 6-year follow-up, participants in the 3-year period were older, more female, had less education, were more likely to live independently, smoked and drank less, and were more frail both in the physical frailty scale and frailty index at baseline.
Table 2 characteristic of the participants at baseline in two survey periods
|
3-year period (2008-2011)
|
6-year period(2008-2014)
|
|
(N = 8425)
|
(N = 5245)
|
Age, mean(SD)
|
82.6 (11.0)
|
79.1 (10.1)
|
Gender:female,n(%)
|
4607(54.7)
|
2800(53.4)
|
Education year, mean(SD)
|
2.4 (3.6)
|
2.6 (3.6)
|
Residenc:Rural, n(%)
|
5207 (61.8)
|
3319 (63.3)
|
Living arrangement: independently, n(%)
|
1368 (16.2)
|
843 (16.1)
|
Relative economic status, n(%)
|
|
|
rich
|
1467 (17.4)
|
873 (16.7)
|
so so
|
5778 (68.7)
|
3622 (69.2)
|
poor
|
1162 (13.8)
|
740 (14.1)
|
Current somker, n(%)
|
1710 (20.3)
|
1178 (22.5)
|
Current drinker, n(%)
|
1670 (19.8)
|
1114 (21.2)
|
Loneliness, n(%)
|
|
|
never
|
3262 (41.9)
|
2208 (43.8)
|
seldom
|
2330 (29.9)
|
1532 (30.4)
|
often
|
2195 (28.2)
|
1301 (25.8)
|
No. of components of frail scale at baseline, mean(SD)
|
1.20 (1.2)
|
0.98 (1.1)
|
Frailty index score at baseline, mean(SD)
|
0.13 (0.1)
|
0.11 (0.1)
|
Frailty transitions
Table 3 shows the transition in frailty status between baseline and follow-up. In 2008 and 2011 waves, nearly half (49.3%) of the participants transitioned between different frailty states (robust, prefrail and frail), 2605(45.3%) remained robust or prefrail state, and 5.3% remained frail states at follow-up. Of the total participants in 2008 and 2014 waves, more than half (51.0%) of participants changed, 1617(45.6%) had maintained robust or prefrail state, and 3.5% remained frail states in follow-up visit. Overall, the frailty transition was similar in the two periods.
There was a clear difference between the distribution of frailty transition among female and male participants. In the two periods, nearly half of male participants remained in the robust or prefrail states, whereas about 40% of female participants remained in the same level. More female participants worsened in physical frailty state than male participants, and male participants had a lower prevalence of remaining frail than females. However, females presented more probability of recovering from greater frailty than males. More than a fifth of the females had improved from greater frailty state in both periods, while 17.3% and 19.5% of males had improved in the two periods respectively.
Table 3 physical frailty transitions between baseline and follow-up, n (%)
|
3 -year period (2008-2011)
|
6-year period (2008-2014)
|
|
Total
|
female
|
male
|
Total
|
female
|
male
|
Remaining robust and prefrail
|
2605(45.3)
|
1160(40.0)
|
1445(50.8)
|
1617(45.6)
|
731(40.9)
|
886(50.3)
|
Worsening
|
1649(28.7)
|
870(30.0)
|
779(27.4)
|
1132(31.9)
|
586(32.8)
|
546(31.0)
|
Improvement
|
1185(20.6)
|
630(21.7)
|
555(19.5)
|
676(19.1)
|
371(20.8)
|
305(17.3)
|
Remaining frail
|
307(5.3)
|
241(8.3)
|
66(2.3)
|
123(3.5)
|
98(5.5)
|
25(1.4)
|
Total
|
5746
|
2901
|
2845
|
3548
|
1786
|
1762
|
chi-squared test for physical frailty transitions by gender in 3-year period: p<0.0001
chi-squared test for physical frailty transitions by gender in 6-year period: p<0.0001
Physical frailty transition as outcome
The associations between physical frailty transition and loneliness are shown in Table 4. In the remaining robust or prefrail group, after adjusting for age, gender, components number in the frail scale and others at baseline, significant trends in remaining frail state was associated with a high level of loneliness observed in the 3-year period: compared to never loneliness participants, those who often felt lonely were unlikely to remain robust or prefrail states (OR=0.78, 95%CI: 0.68 - 0.91, p<0.01). In the worsening group, loneliness was a significant risk factor in that a high level of loneliness was associated with worsened frailty states after years (3-year period: OR=1.19, 95%CI: 1.01 - 1.41, p<0.05;6-year period: OR=1.34, 95%CI: 1.08 - 1.66, p<0.01). In the improvement group, loneliness showed no significant influence on frailty transition. Loneliness at baseline was positively associated with remaining frail in the 6-year period (seldom loneliness: OR=2.47, 95%CI: 1.25 - 4.85, p<0.01) but no significant association had shown in the 3-year period.
We also investigated whether the association between loneliness and physical frailty transition differed by gender. Male participants who felt lonely often were negatively related to remaining robust and prefrail (3-year period: OR=0.73, 95%CI: 0.59 - 0.89, p<0.01;6-year period: OR=0.75, 95%CI: 0.57 - 0.99, p<0.05), and positively related to worsening frail (3-year period: OR=1.37, 95%CI: 1.07 - 1.75;6-year period: OR=1.54, 95%CI: 1.13 - 2.11) in the two survey periods. Loneliness of male participants was also found to be related to remaining frail after 6 years (seldom loneliness: OR=12.68, 95%CI: 1.66 - 96.71, p<0.05).
Table 4 odds ratios (95% CI) for physical frailty transitions and loneliness
|
3 -year period (2008-2011)
|
6-year period (2008-2014)
|
Remaining robust and prefrail
|
Worsening
|
Improvement
|
Remaining frail
|
Remaining robust and prefrail
|
Worsening
|
Improvement
|
Remaining frail
|
Total
|
|
|
|
|
|
|
|
|
never
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
seldom
|
0.99
|
1.05
|
1.03
|
1.15
|
0.98
|
1.02
|
0.99
|
2.47**
|
|
(0.87 - 1.13)
|
(0.90 - 1.21)
|
(0.86 - 1.23)
|
(0.76 - 1.73)
|
(0.83 - 1.15)
|
(0.85 - 1.22)
|
(0.77 - 1.26)
|
(1.25 - 4.85)
|
often
|
0.78**
|
1.19*
|
1.14
|
1.00
|
0.84
|
1.34**
|
0.85
|
1.88
|
|
(0.68 - 0.91)
|
(1.01 - 1.41)
|
(0.94 - 1.39)
|
(0.67 - 1.51)
|
(0.70 - 1.01)
|
(1.08 - 1.66)
|
(0.65 - 1.12)
|
(0.93 - 3.79)
|
Female
|
|
|
|
|
|
|
|
|
never
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
seldom
|
1.00
|
1.01
|
1.02
|
1.17
|
1.01
|
1.12
|
0.77
|
1.77
|
|
(0.83 - 1.21)
|
(0.82 - 1.25)
|
(0.79 - 1.32)
|
(0.73 - 1.87)
|
(0.80 - 1.28)
|
(0.86 - 1.46)
|
(0.55 - 1.08)
|
(0.83 - 3.77)
|
often
|
0.85
|
1.04
|
1.07
|
0.96
|
0.94
|
1.20
|
0.78
|
1.40
|
|
(0.69 - 1.05)
|
(0.82 - 1.32)
|
(0.82 - 1.40)
|
(0.60 - 1.53)
|
(0.73 - 1.21)
|
(0.89 - 1.60)
|
(0.55 - 1.10)
|
(0.65 - 3.02)
|
Male
|
|
|
|
|
|
|
|
|
never
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
seldom
|
0.99
|
1.08
|
1.03
|
1.35
|
0.96
|
0.92
|
1.28
|
12.68*
|
|
(0.83 - 1.18)
|
(0.88 - 1.33)
|
(0.80 - 1.34)
|
(0.55 - 3.32)
|
(0.77 - 1.20)
|
(0.71 - 1.18)
|
(0.90 - 1.82)
|
(1.66 - 96.71)
|
often
|
0.73**
|
1.37*
|
1.25
|
1.37
|
0.75*
|
1.54**
|
0.94
|
8.89
|
|
(0.59 - 0.89)
|
(1.07 - 1.75)
|
(0.93 - 1.68)
|
(0.58 - 3.24)
|
(0.57 - 0.99)
|
(1.13 - 2.11)
|
(0.61 - 1.44)
|
(0.75 - 105.30)
|
***P<0.001, **P<0.01, *P<0.05;
Sample size: 2008-2011 waves: total participants: 5689; for female participants:2866; for male participants:2823;
2011-2014 waves: total participants: 3529; for female participants:1776; for male participants:1753.
Notes: Model had been adjusted for age, components number in the frail scale at baseline, residence, education year, living arrangement, relative economic status, smoking and drinking alcohol at baseline. In total participants, adjustment for gender was also performed.
Frailty Index as outcome
Table 5 presents odds ratios (95%CI) for change in the frailty index and loneliness. Loneliness at baseline was observed to be a protective factor for the improvement of frailty index only in 3-year period (seldom loneliness: OR= 1.42, 95%CI: 1.04 - 1.95, p<0.05; often loneliness: OR= 1.50, 95%CI: 1.08 - 2.08, p<0.05).In terms of 6-year period, loneliness at baselines was found to increase the possibility of participants to remain frail (seldom loneliness: OR= 1.78, 95%CI: 1.25 - 2.55, p<0.01; often loneliness: OR= 1.74, 95%CI: 1.21 - 2.50, p<0.01) after 6 years.
There were also gender differences in the transition type of frailty index and loneliness. Loneliness in male participants tends to be related to remaining in frail in 6-year period (seldom loneliness: OR= 3.58, 95%CI: 1.73 - 7.41, p<0.001; often loneliness: OR=2.70, 95%CI: 1.27 - 5.76, p<0.01), but no significant relationship was found in female participants. A high level loneliness in female participants was associated with improvement of frailty in 3-year period (OR= 1.54, 95%CI: 1.02 - 2.31, p<0.05). The association between loneliness and frailty index in male participants was the same with that found in all participants, except that no relationship with improvement of frailty index in the 3-year period was observed in male participants with seldom loneliness.
Table 5 odds ratios (95% CI) for transition type in frailty index and loneliness
|
3 -year period (2008-2011)
|
6-year period (2008-2014)
|
|
Remaining nonfrail
|
Worsening
|
Improvement
|
Remaining frail
|
Remaining nonfrail
|
Worsening
|
Improvement
|
Remaining frail
|
Total
|
|
|
|
|
|
|
|
|
never
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
seldom
|
1.03
|
0.94
|
1.42*
|
1.03
|
0.99
|
0.93
|
0.76
|
1.78**
|
|
(0.87 - 1.20)
|
(0.79 - 1.11)
|
(1.04 - 1.95)
|
(0.82 - 1.30)
|
(0.82 - 1.20)
|
(0.77 - 1.13)
|
(0.47 - 1.22)
|
(1.25 - 2.55)
|
often
|
0.89
|
0.96
|
1.50*
|
1.07
|
0.83
|
1.00
|
0.88
|
1.74**
|
|
(0.75 - 1.05)
|
(0.80 - 1.16)
|
(1.08 - 2.08)
|
(0.84 - 1.36)
|
(0.67 - 1.02)
|
(0.80 - 1.24)
|
(0.54 - 1.42)
|
(1.21 - 2.50)
|
Female
|
|
|
|
|
|
|
|
|
never
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
seldom
|
1.20
|
0.89
|
1.12
|
0.93
|
1.02
|
0.98
|
0.65
|
1.39
|
|
(0.96 - 1.49)
|
(0.71 - 1.11)
|
(0.73 - 1.72)
|
(0.70 - 1.23)
|
(0.78 - 1.33)
|
(0.76 - 1.28)
|
(0.35 - 1.22)
|
(0.92 - 2.10)
|
often
|
0.96
|
0.87
|
1.54*
|
0.98
|
0.77
|
1.04
|
0.93
|
1.50
|
|
(0.77 - 1.21)
|
(0.68 - 1.10)
|
(1.02 - 2.31)
|
(0.73 - 1.31)
|
(0.58 - 1.01)
|
(0.79 - 1.38)
|
(0.51 - 1.67)
|
(0.99 - 2.27)
|
Male
|
|
|
|
|
|
|
|
|
never
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
Ref.
|
seldom
|
0.87
|
0.97
|
2.00**
|
1.30
|
0.96
|
0.88
|
0.95
|
3.58***
|
|
(0.69 - 1.10)
|
(0.76 - 1.25)
|
(1.23 - 3.24)
|
(0.86 - 1.96)
|
(0.73 - 1.27)
|
(0.66 - 1.16)
|
(0.46 - 1.98)
|
(1.73 - 7.41)
|
often
|
0.84
|
1.05
|
1.41
|
1.35
|
0.94
|
0.95
|
0.77
|
2.70**
|
|
(0.64 - 1.09)
|
(0.79 - 1.39)
|
(0.81 - 2.44)
|
(0.88 - 2.05)
|
(0.68 - 1.30)
|
(0.68 - 1.33)
|
(0.34 - 1.77)
|
(1.27 - 5.76)
|
***P<0.001, **P<0.01, *P<0.05.
Sample size: 2008-2011 waves: total participants: 5548; female participants:2833; male participants:2715;
2011-2014 waves: total participants: 3381; for female participants:1737; for male participants:1644.
Notes: Model had been adjusted for age, components number of frail scale at baseline, residence, education year, living arrangement, relative economic status, smoking and drinking alcohol at baseline. In total participants, adjustment for gender was also performed.