Prevalence of frailty
At baseline, population without diabetes was 6410, 875 were pre-diabetics and 2634 were diabetics, of which a total of 1373 were frail (Table
1). The highest prevalence of frailty was found in the population with diabetes (19.32%), whereas prevalence of frailty in pre-diabetics (11.43%) and non-diabetes (11.92%) population was quiet similar. The prevalence of frailty was found to be higher in female compared to male in all 3 groups ie non-diabetes, pre-diabetes and diabetes (13.16%, 13.71%, 21.05% vs 9.97%, 8.12%, 16.39%) respectively, urban population were distinctively frail compared to rural (14.51%, 14.70%, 22.25% vs 2.93%, 3.52%, 5.62%) in the 3 groups. The prevalence of frailty was found to increase with age and was highest in oldest of old age group ≥85 (28.83%, 47.62%, 42.31%). Prevalence of frailty increased with the number of co-morbidity in all 3 groups; highest in subjects with 3 or more co-morbidity (43.56%, 45.90%, 49.34%). Similarly, prevalence increased with polypharmacy, subjects with 4 or more medications per day had higher prevalence of frailty (33.24%, 36.67%, 36.19%) in the 3 groups, respectively.
Table 1
Prevalence and incidence of frailty by blood glucose status
Overall | 764 (11.92) | 100 (11.43) | 509 (19.32) | <.0001 | 283 (7.04) | 50 (8.73) | 194 (12.32) | <.0001 |
Residence |
Urban | 722 (14.51) | 91 (14.70) | 483 (22.2) | <.0001 | 247 (7.76) | 45 (10.71) | 184 (14.10) | <.0001 |
Rural | 42 (2.93) | 9 (3.52) | 26 (5.62) | 0.0254 | 36 (4.31) | 5 (3.27) | 10 (3.70) | 0.7925 |
Gender |
Male | 249 (9.97) | 29 (8.12) | 160 (16.39) | <.0001 | 95 (5.82) | 21 (8.57) | 61 (9.65) | 0.0038 |
Female | 515 (13.16) | 71 (13.71) | 349 (21.05) | <.0001 | 188 (7.87) | 29 (8.84) | 133 (14.10) | <.0001 |
Age group |
55–64 | 70 (3.84) | 8 (3.00) | 51 (8.12) | <.0001 | 33 (2.76) | 8 (4.44) | 19 (4.62) | 0.1370 |
65–74 | 285 (10.51) | 41 (11.17) | 2013 (17.67) | <.0001 | 114 (6.36) | 23 (9.24) | 81 (11.22) | 0.0002 |
75–84 | 362 (21.17) | 41 (18.64) | 234 (28.85) | <.0001 | 116 (12.17) | 18 (13.14) | 86 (20.33) | 0.0003 |
≥85 | 47 (28.83) | 10 (47.62) | 22 (42.31) | 0.0712 | 20 (25.32) | 1 (14.29) | 8 (42.11) | 0.2433 |
Coexisting co-morbidity |
0 | 16 (0.78) | 1 (0.39) | 11 (1.99) | 0.0237 | 42 (3.09) | 7 (4.09) | 29 (7.55) | 0.0005 |
1–2 | 356 (10.27) | 43 (8.65) | 200 (13.55) | 0.0007 | 174 (7.69) | 31 (8.88) | 95 (9.88) | 0.1164 |
≥3 | 392 (43.56) | 56 (45.90) | 298 (49.34) | 0.0877 | 67 (16.92) | 12 (22.64) | 70 (30.57) | 0.0004 |
Polypharmacy/day |
0–3 | 409 (7.70) | 45 (6.25) | 149 (9.19) | 0.0353 | 206 (5.97) | 41 (8.47) | 116 (10.84) | <.0001 |
≥4 | 354 (33.24) | 55 (36.67) | 359 (36.19) | 0.3299 | 75 (13.69) | 9 (10.59) | 74 (15.04) | 0.5210 |
Anti-diabetic medication |
Never | / | / | 68 (10.86) | | / | / | 36 (8.82) | 0.1794 |
Occasionally | / | / | 11 (22.00) | | / | / | 5 (15.63) | |
Regularly | / | / | 430 (21.96) | | / | / | 153 (13.48) | |
BMI status |
<19 | 58 (22.75) | 4 (23.53) | 19 (30.65) | 0.4275 | 12 (9.30) | 0 | 1 (2.94) | 0.3112 |
19–28 | 547 (10.61) | 64 (9.61) | 373 (18.18) | <.0001 | 224 (6.85) | 34 (7.71) | 148 (11.94) | <.0001 |
≥28 | 154 (15.88) | 32 (17.11) | 114 (22.53) | 0.0065 | 47 (7.83) | 16 (13.33) | 43 (14.68) | 0.0040 |
Hours of outdoor activity/day |
0 | 93 (32.18) | 13 (28.26) | 57 (43.18) | 0.0545 | 7 (5.74) | 4 (15.38) | 4/49 (8.16) | 0.2389 |
<0.5 h | 171 (15.21) | 26 (16.05) | 127 (26.19) | <.0001 | 51 (7.10) | 16 (14.16) | 44 (15.88) | <.0001 |
0.5–1 h | 353 (12.32) | 46 (13.03) | 227 (18.49) | <.0001 | 146 (7.71) | 20 (8.62) | 93 (12.13) | 0.0014 |
2–3 h | 125 (8.09) | 13 (5.99) | 83 (13.65) | <.0001 | 58 (6.24) | 10 (7.04) | 43 (11.75) | 0.0036 |
≥4 h | 22 (3.88) | 2 (2.13) | 15 (8.47) | 0.0189 | 21 (6.12) | 0 (0) | 10 (8.93) | 0.0680 |
Doing or helping with house work |
Never | 160 (22.22) | 23 (20.18) | 116 (29.90) | 0.0096 | 33 (9.02) | 6 (10.53) | 31 (15.82) | 0.0517 |
Occasionally | 252 (11.09) | 41 (12.89) | 173 (18.21) | <.0001 | 111 (7.61) | 22 (10.38) | 73 (12.56) | 0.0017 |
Regularly | 352 (10.30) | 36 (8.13) | 220 (16.98) | <.0001 | 139 (6.34) | 22 (7.24) | 90 (11.28) | <.0001 |
Incidence of frailty
A total of 7,314 older adults were followed up at 12 months, of which 6,293 were eligible subjects (Table
1). At one year follow-up, 527 new cases of frailty were detected, and the overall incidence of frailty increased from non-diabetes to pre-diabetes and diabetes group (7.04, 8.73, 12.32%, p < 0.001). Such increasing trends were also found in other demographic and clinical subpopulations. For instance, the incidence in females were increased by glucose status (7.87, 8.84, 14.10%) compared to those in the males (5.82, 8.57, 9.65%) in non-diabetic, pre-diabetic and diabetic subjects respectively. For age group between 55 to 64, the incidence of frailty was the lowest compared with other age groups, but the incidence in pre-diabetic and diabetic subjects were both significantly higher than subjects with normal glucose, 2.76% vs. 4.44% vs. 4.62%, respectively. For subgroups aged 65–74 and 75–84 years, the incidence also increased from 6.36% to 9.24 and 11.22% and from 12.17% to 13.14 and 20.33%, respectively. For the oldest age group, there was not enough data in pre-diabetic subjects to show the increasing trend, but the incidence rate in diabetic subjects was much higher than non-diabetes (42.11% vs. 25.32%).
Crude and adjusted risks of frailty comparing pre-diabetic and diabetic subjects with those with normal blood glucose at baseline and follow-up survey
Using both unadjusted and adjusted logistic regression, we found having diabetes increased the risk of prevalence frailty at baseline (Additional file
2: Table S2 Appendix 2), the crude and adjusted OR were 1.77 (95%CI = 1.56–2.00,
P < .0001), and 1.36 (95%CI = 1.18–1.56,
P < .0001), controlling for age, sex, residency and co-morbidity. However, the prevalence of frailty in pre-diabetics was not statistically higher than those in non-diabetics (unadj. OR = 0.95, adj. OR = 0.96). For longitudinal risk of frailty at one-year follow-up visit, subjects with diabetes were statistically higher than those with normal blood glucose using both unadjusted RR (1.75, 95%CI = 1.47–2.08,
p < 0.001) and adjusted RR by age, sex, residency and comorbidity (adj. RR = 1.56, 95%CI = 1.32–1.85,
p < .0001). Pre-diabetics also showed an increased risk of frailty, the unadjusted RR and adjusted RR were 1.24 (95%CI = 0.93–1.65,
p = 0.1439) and 1.28 (95%CI = 0.96–1.70,
p = 0.0886) respectively, however didn't reach the statistical significant level.
Associated factors for risk of prevalence of frailty in elevated blood glucose (pre-diabetic and diabetic) population and normal blood glucose (non-diabetic) population
In Table
2, we stratified the baseline participants by blood glucose level status, ie. elevated blood glucose (pre-diabetes and diabetes) and normal blood glucose (non-diabetic) and developed multiple logistic model of frailty for each stratum. Both strata shared four common risk factors and three protective factors for frailty, including urban living (adj. ORs = 2.29 and 3.07 in elevated and normal glucose group, respectively), less than 6-h sleep per day (adj. ORs = 1.56 and 1.48), with comorbidity (adj. ORs = 6.33 and 11.82 for having 1–2 diseases; 43.56 and 60.46 for having 3 or more diseases), polypharmacy (adj. ORs = 3.44 and 2.50), and being married (adj. ORs = 0.60 and 0.66, more hours of outdoor activity (adj. ORs = 0.24 to 0.20 and 0.23 to 0.19) and helping with house work regularly (adj. ORs = 0.56 and 0.43). Three more risk factors were found in pre-diabetic and diabetic subgroup, such as low education (adj. OR = 1.60), irregular life style (adj. OR = 4.74), not often drinking milk (adj. OR = 1.61). Being female and older age statistically increased the prevalence of frailty only in non-diabetes subpopulation.
Table 2
Backward elimination variable selection method to investigate if the elevated blood glucose (pre-diabetes and diabetes) frail population shared common risk factors as other frail population at baseline
Male vs female | / | / | / | 0.66 | (0.50,0.87) | 0.0031 |
Currently married vs not | 0.60 | (0.43,0.85) | 0.0041 | 0.66 | (0.50,0.88) | 0.0052 |
Urban vs rural | 2.29 | (1.30,4.05) | 0.0022 | 3.07 | (1.85,5.09) | <.0001 |
Age group |
55–64 | / | / | / | Ref | Ref | Ref |
65–74 | / | / | / | 1.60 | (1.09,2.37) | 0.0649 |
75–84 | / | / | / | 2.33 | (1.56,3.49) | 0.1907 |
≥85 | / | / | / | 4.25 | (2.04,8.83) | 0.0026 |
Low education vs higher | 1.60 | (1.18,2.15) | 0.0022 | / | / | / |
Not regular lifestyle vs regular | 4.74 | (2.02,11.14) | 0.0004 | / | / | / |
Not Regularly drinking milk vs regular | 1.61 | (1.19,2.18) | 0.0020 | / | / | / |
Less than 6 h/day sleep vs more sleep | 1.56 | (1.11,2.20) | 0.0100 | 1.48 | (1.12,1.96) | 0.0053 |
Number of comorbiditya
| | | | | | |
0 | Ref | Ref | Ref | Ref | Ref | Ref |
1–2 | 6.33 | (2.70,14.80) | 0.8612 | 11.82 | (5.49, 25.42) | 0.0489 |
≥3 | 43.56 | (18.40,103.16) | <.0001 | 60.46 | (27.72, 131.88) | <.0001 |
Polypharmacy ≥4 types/day | 3.44 | (2.57,4.62) | <.0001 | 2.50 | (1.93,3.22) | <.0001 |
Hours of outdoor activity daily |
None | Ref | Ref | Ref | Ref | Ref | Ref |
0.5–1 h | 0.31 | (0.17,0.54) | 0.3381 | 0.26 | (0.17, 0.41) | 0.0660 |
2–3 h | 0.24 | (0.12,0.45) | 0.0247 | 0.229 | (0.14, 0.38) | 0.0129 |
≥4 h | 0.20 | (0.08,0.50) | 0.0559 | 0.190 | (0.09,0.40) | 0.0291 |
Doing or helping with house work |
Never | Ref | Ref | Ref | Ref | Ref | Ref |
Occasionally | 0.80 | (0.52,1.24) | 0.6714 | 0.66 | (0.44, 0.97) | 0.9925 |
Regularly | 0.56 | (0.37,0.85) | 0.0029 | 0.43 | (0.29, 0.63) | <.0001 |
Associated factors for risk of incidence of frailty in elevated blood glucose (pre-diabetic and diabetic) population and normal blood glucose (non-diabetic) population
In Table
3
, we investigated the risk factors of incidence of frailty longitudinally by blood glucose status subpopulation using separate multiple logistic models. The common risk factors for frailty incidence in both populations were age (adj. RR = 1.70, 2.62, 4.88 and 2.01, 3.49, 7.72 in elevated and normal glucose groups, respectively), and comorbidity (adj. RR = 1.19 and 2.13 for 1–2 diseases, 3.02 and 3.43 for 3 or more diseases, respectively); and the common protective factor was receiving regular medical consultation (adj. RR = 0.79 and 0.72 in elevated and normal glucose groups, respectively). Two risk factors including urban-living (adj. RR = 2.28), higher waist circumference (adj. RR = 1.37) and two protective factors including being male (adj. RR = 0.67),doing house work regularly (adj. RR = 0.67) were only among pre-diabetes and diabetes subjects. For the non-diabetic participants polypharmacy was a risk factor of frailty (adj. RR = 1.44) and awareness of their blood glucose status was protective against frailty (adj. RR = 0.72).
Table 3
Backward elimination variable selection method to investigate if the elevated blood glucose (pre-diabetes and diabetes) frail population shared common risk factors as other frail population at one-year follow-up
Male vs female | 0.67 (0.52,0.86) | 0.0017 | / | / |
Urban vs rural | 2.28 (1.32, 3.91) | 0.0030 | / | / |
Age group |
55–64 | Ref | Ref | Ref | Ref |
65–74 | 1.70 (1.12, 2.58) | 0.0125 | 2.01 (1.37,2.93) | 0.0003 |
75–84 | 2.62 (1.71, 4.03) | <.0001 | 3.49 (2.38,5.12) | <.0001 |
≥85 | 4.88 (2.53, 9.42) | <.0001 | 7.72 (4.61,12.94) | <.0001 |
Regularly receiving medical consultation after baseline vs not receiving | 0.79 (0.62,1.00) | 0.0463 | 0.72 (0.58, 0.90) | 0.0041 |
Regular anti diabetic treatment vs irregular | 1.16 (0.91, 1.48) | 0.2240 | / | / |
Number of comorbiditya
|
0 | Ref | Ref | Ref | Ref |
1–2 | 1.19 (0.83,1.70) | 0.3386 | 2.13 (1.53, 2.98) | <.0001 |
≥3 | 3.02 (2.07,4.39) | <.0001 | 3.43 (2.30, 5.12) | <.0001 |
Polypharmacy ≥4 types/day | / | / | 1.44 (1.11, 1.86) | 0.0062 |
Doing or helping with house work |
Never | Ref | Ref | / | / |
Occasionally | 0.87 (0.61,1.24) | 0.4344 | / | / |
Regularly | 0.67 (0.47,0.95) | 0.0247 | / | / |
Waist circumference high vs normal | 1.37 (0.99,1.89) | 0.0549 | / | / |
Self-awareness of blood glucose level | / | / | 0.72 (0.57, 0.90) | 0.0036 |
Discussion
Our results for the overall prevalence and incidence of frailty in the population without diabetes and with diabetes are consistent with previous studies [
6‐
8,
12,
19‐
23]. Both rates were found to be the most lowest in older population without diabetes, slightly higher in pre-diabetic and highest in diabetic population. Such increasing trends of frailty by blood glucose level were similarly found in age and other demographic subgroups, showing diabetes is an independent predictor of the prevalence and incidence of frailty. Whereas, pre-diabetes or impaired fasting glucose although not very distinct could be playing an intermediary role along with other risk factors in the acceleration of frailty. Therefore, attention should be given to the elderly population with impaired fasting glucose levels as well. Older adults with more co-morbidity and taking more medications were found to have a very high prevalence and incidence of frailty in all three groups (ie non-diabetics, pre-diabetics and diabetics), indicating that frailty is severely affected by multi co-morbidity and polypharmacy, which is in consistent with previous studies [
6‐
8,
19‐
23], and if were additionally to be affected with pre-diabetes or diabetes, the condition could worsen [
24,
25]. More importantly, elderly population with pre-diabetes are known to have low grade systemic inflammation and oxidative stress [
25], leading to metabolic dysfunction which may affect the components of physical frailty, therefore should not be ignored. Therefore, physicians should advise older adults to follow proper blood sugar control techniques at an early phase of abnormal blood glucose status.
Elevated blood glucose populations shared some common risk factors as non-diabetic populations in both cross-sectional and longitudinal analysis. At baseline, the following subgroups demonstrated higher prevalence of frailty despite of blood glucose status: not being married, urban residency, daily sleep less than 6 h, co-morbidity, polypharmacy, less outdoor activity time and rarely helping with house work. To screen more people with frailty in community, elderly subjects with above characteristics should be targeted. However, lower education and irregular life style and less intake of milk were only correlated with the prevalence of frailty in pre-diabetic and diabetic subjects. In contrast, advanced age and being female were positively associated with frailty only among subjects with normal blood glucose. In light of this, health care providers should consider screening for frailty of at-risk older people and followed by targeted interventions for deficit or risk issues. The different sets of risk factors for normal and elevated blood glucose subgroups have been identified using longitudinal data. Among pre-diabetic and diabetic older subjects, the unmodifiable risk factors were female sex, urban living, and modifiable risk factors were higher waist-circumference, less house work and in need of taking regular anti-diabetic medication. Among older adults with normal blood glucose, only poly-pharmacy and unawareness of blood glucose were found to be independent risk factor of developing frailty. Therefore, the interventions in community health centers among non-diabetic subjects should target on consultation on polypharmacy prescription and improving individual's awareness of blood glucose level. Considering the serious and worse adverse events among frail older people with diabetes, screening and intervention of frailty should be proactively implemented as soon as pre-diabetes is detected.
Consistent with previous studies, doing regular household work and performing more outdoor activity had positive effect for frail older adults [
26‐
28]. Therefore, routinely proper physical activities, participation in more house work and losing waist for those with higher waist circumference should be an urgent need to prevent frailty in elderly subjects [
29‐
31]. Our study has also demonstrated some more protective factors of frailty, such as drinking milk, maintaining regular daily life-style and awareness blood glucose level and getting routinely geriatric health consultation. Geriatricians and physicians should take in account of these factors while advising the older patients.
Our study is the first to show the relationship of elevated blood glucose status with frailty in Chinese older adults. However, some limitations of this study are worth mentioning: we used fasting plasma glucose, personal history of diagnosis of diabetes and use of anti-diabetic medication as the diagnosis criteria for pre-diabetes and diabetes, oral glucose tolerance testing was not taken (as it is in-practicable for such a large cohort) and glycosylated hemoglobin (HbA1c) levels were not measured which might have misclassified some of the participants. Future studies in the subject could focus in the limitation of this study. And more studies are warranted on dose–response relationship and their etiology rationale between blood glucose level and frailty, as well as cost-effectiveness analyses on managing frailty among pre-diabetes and diabetes in various community settings.