The risk factors and mortality in elderly patients with different glomerular filtration rate after hip fracture

doi:10.21203/rs.3.rs-2616138/v1

Background: The aim of our study was to explore short- and long-term mortality and risk factors affecting Chinese elderly patients with different glomerular filtration rate after hip fracture.

Methods: This study included 513 patients aged≥65 years old and first been diagnosed with hip fracture in the Department Orthopedics of Huadong hospital between January 1st, 2010 and December 31st, 2011. Patients’ medical records were collected from the electronic medical record system. Survival status after hip fracture were assessed through telephone interviews and causes of death were verified. The patients were divided into three groups according to the renal function. Kaplan-Meier survival analysis was used to compare survival time between different groups. Univariate and multivariate Cox proportional hazards model was constructed to analyze differences between patients and factors associated with mortality.

Results: According to the inclusion and exclusion criteria and excluded patients who were lost to follow-up, a total of 325 patients were available in this study. Of which 73.5% were female and 85.2% received surgical operation. One-year cumulative mortality were 9.30%, 19.81% and 22.53% for group 1, 2 and 3. Five-year cumulative mortality were21.87%, 55.86% and 78.87%, while the ten-year cumulative mortality were40.61%, 74.32% and 94.37% respectively. Our analysis found that age (1.076 (1.031-1.122)), cognitive function (2.279(1.101-4.718)) were associated with higher risk of one-year mortality. Age (1.062(1.035-1.090)), eGFR<60 mL/min/1.73m²(2.425(1.054-5.578)) were associated with higher risk of five-year mortality. Age(1.073(1.049-1.097)), eGFR<60 mL/min/1.73m²(2.120(1.110-4.048)) and mildly decreased cognitive function(1.949(1.163-3.265)) were associated with higher risk of ten-year mortality.

Conclusion: Renal function seem to have little effect on short term mortality of Chinese elderly patients after hip fracture, but was an important risk factor affecting the medium to long-term mortality. For patients with decreased eGFR, fully evaluating the status of patients and choosing appropriate surgical method as soon as possible after fracture can greatly reduce the risk of death and ensure better survival in the elderly.

Estimated glomerular filtration rate

Hip fracture

Osteoporosis

Mortality

Older people

It is estimated that there were more than 850 million people suffer from kidney disease due to various reasons. The global prevalence of chronic kidney disease (CKD) was 14.3%[1]. In China, 119.5 million adults over the age of 18 years old suffer from CKD, accounting for 10.8% of the total population. Among them, those aged 60–79 years old accounted for 13.2% and 64.1% are over 80 years old[2]. CKD causes at least 2.4 million people died per year and has been the sixth fastest-growing cause of death currently. Chronic kidney disease-mineral and bone disorder (CKD-MBD) is one of the most common complications in patients, which lead to calcium and phosphorus metabolism disorders and secondary hyperparathyroidism and increase the risk of fracture[3–5].

Compared with general population, fragile fractures were common with advancing age in CKD patients and resulted in excess morbidity, mortality and heath care costs[6]. A meta-analysis showed that approximately 2% of dialysis patients suffer from hip fractures, and the overall prevalence rate is 8.95 per 1,000 people. Fractures occurs 13 to 16 years earlier and the overall risk of hip fracture was more than 5-fold higher in dialysis patients than that in the general population. The mortality rate of hip fractures in patients with ESRD is more than three times that of non-CKD patients[7, 8]. The mechanism of fragility fractures has not been elucidated in detail in Chinese elderly patients with CKD.

Whereas due to the disturbances in mineral metabolism of CKD patients, some fracture risk assessment tools may not accurately predict fracture in individuals with reduced kidney function[9]. And there were few prospective studies exploring the risk factors of fragility fractures in patients with non-dialysis CKD. The fracture risk and long-term mortality of patients with different glomerular filtration rate (eGFR) are still unknown in Chinese elderly population. Thus, the aim of our study was to explore short- and long-term mortality and risk factors affecting Chinese elderly patients with different glomerular filtration rate after hip fracture.

Study population

A total of 513 patients aged≥65 years old and first been diagnosed with hip fracture in the Department Orthopedics, Huadong hospital between January 1st, 2010 and December 31st, 2011 were included. For this analysis, we included individuals who met the following criteria: (1) men and women who aged≥65 years, (2)individuals received at least one kidney function test, and (3) those who had being diagnosed with hip fracture. We excluded patients with at least one of the following: (1)under the age of 65 years old, (2)had violent fracture or previous fracture history, and (3)fracture secondary to bone tumor or metastasis. Of the 513 patients, 5 patients had fracture caused by climbing down,7 had external force collision, 15 had traffic accident, 8 had pathological fracture, 10 had other reasons causing fracture, and 12 further cases had insufficient or incomplete clinical records. Finally, a total of 456 patients were included for survival analysis, of which 80 patients lost to follow-up in the fifth year and 51 patients lost to follow-up in the tenth year (Figure 1).

This study complied with the Declaration of Helsinki. All patients signed informed consent. And its protocol was approved by the Ethics Committee of Huadong Hospital (2017K038).

Clinical data collection and tested

During hospitalization, the patients’ medical records were collected from the electronic medical record system: the patients’ basic information (name, sex, age, weight, height, origin, occupation, educational background), pre-fracture conditions (physical condition, history of fracture, medication history, dietary habits, smoking history, drinking history, cognitive function, cardiac function), cause of hip fracture (fall, slide, obstacles, climb, rub, traffic accident, disequilibrium due to illness, pathological fracture, other). Data on blood samples including Hemoglobin (Hb), albumin (ALB), blood glucose (BG), blood urea nitrogen (BUN), serum creatinine (SCR), alanine aminotransferase (ALT), potassium(K+), sodium (Na+), calcium (Ca2+), phosphate (P) were collected before and after treatment. Other information like fracture type, treatment modalities, anesthesia type, surgical type, perioperative blood transfusion, length of stay and hospitalization costs were also collected from the electronic medical record system.

Body mass index (BMI) was calculated from formula BMI = weight/height²,expressed in kg/m². The estimated glomerular filtration rate (eGFR) (mL/min/1.73m²), was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. According to the data of eGFR, we divided the patients into three groups: ≥90mL/min/1.73m²(Group 1), 60-89mL/min/1.73m² (Group 2), ＜60mL/min/1.73m² ( Group 3).

Patient’s survivals were followed up by telephone and recorded in the Case Report Form (CRF). Follow-up time was calculated from the date of a hip fracture-related hospital admission to date of death. Subjects who survived till the end of the study were treated as censored.

Statistical analysis

All statistical were analyzed using SPSS 26.0 and the statistical chart were described by GraphPad Prism 8.0. Continuous variables for normal distribution were tested with Shapiro–Wilk test. Continuous variables with normal distribution were presented as mean ± standard while abnormal distribution statistics were described as the median with the interquartile range. Categorical variables are showed as percentages. A one-way analysis of variance (ANOVA) was used to compare the difference between the normal variables. If the variables were homogeneous, the Turkey-Kramer test were used and if not homogeneous, Games-Howell test were applied. The chi-square test and the Fisher’s exact test were used to identify any significant association between categorical variables. The correlation of two variables of normal distribution was determined using a Pearson correlation analysis, and correlation of two non-normal distributed variables was determined using a Spearman correlation analysis.

Kaplan-Meier survival analysis was used to compare survival time between different groups. Univariate and multivariate Cox proportional hazards model was constructed to analyze differences between patients and factors associated with mortality. Results were expressed as hazard ratio (HR) with their corresponding 95% confidence interval (CI). P<0.05 is considered statistically significant.

Relationship between different eGFR and clinical characteristics

Data on 325 hip fracture patients were available, of which 73.5% (n=239) were female and 26.5%(n=86) were male, with a mean age of 82.64±6.41 years. Among those patients, 58.2%(n=189) had intertrochanteric fracture, 41.2% (n=134) had femoral neck fracture, 0.6% patients(n=2) had femoral head fracture, 85.2% (n=277) received surgical operation, 14.8% (n=48) chose non-surgical treatment. By the end of the last follow-up, the mean survival time of the three groups was 7.49±3.24 years, 4.87±3.57 years and 3.16±2.56 years, respectively, and the survival time of group 1 was significantly higher than that of group 2 and group 3 (P<0.001). Comparing with group 3, group 1 and group 2 (P<0.001) had higher Hb level. In the sub-groups of patients who received operation, the probability of perioperative blood transfusion in group 2 and group 3(P=0.013) was significantly higher than that in group 1. (Table 1, 2)

Cumulative mortality

Kaplan-Meier survival analysis shows that the median survival time for group 2 and group 3 were 4.14 years and 2.85 years. The mortality among the three groups are significantly different (P<0.001) (Figure 2). One-year cumulative mortality were 9.30%, 19.81% and 22.53% for group 1, 2 and 3. Five-year cumulative mortality was 21.87%, 55.86% and 78.87%, while the ten-year cumulative mortality was 40.61%, 74.32% and 94.37% respectively. The total mortality rate of ten-year were significantly higher than five-year mortality (χ²=57.95, P<0.001). (Table 3; Figure 3)

Risk factors affecting one-year mortality after hip fracture

The multivariate regression Cox analysis shows age, cognitive function, operation were factors that affect the 1-year mortality of patients after hip fracture. With every increase of age, the mortality rate increased 1.076 times (95% confidence interval [CI], 1.031-1.122; P =0.001). Patients with mild cognitive function decline had a 2.279 times higher hazard ratio [HR] than people with normal cognitive function (95% CI, 1.101-4.718; P=0.026). Patients receiving surgical operation had a 0.357 time (95%CI, 0.204-0.628; P<0.001) lower HR than the patients chose non-surgical therapy. (Figure 4)

Risk factors affecting five-year mortality after hip fracture

The multivariate regression Cox analysis shows gender, age, albumin, kidney function, cognitive function, operation were all factors that affect the 5-year mortality of patients after hip fracture. Female had a 0.691 time (95% CI, 0.503-0.949; P =0.023) lower HR than male. Patients receiving surgical operation had a 0.412 time (95%CI, 0.288-0.589; P<0.001) lower HR than the patients chose conservative therapy. With every increase of age, the mortality rate increased 1.062 time (95% CI, 1.035-1.090; P <0.001). Patients in group 3 had a 2.425 times higher HR than group 1(95% CI, 1.054-5.578; P = 0.037). Patients with mild cognitive function decline had a 2.065 times HR than people in normal cognitive function (95% CI, 1.207-3.533; P = 0.008). ( Figure 5)

Risk factors affecting ten-year mortality after hip fracture

The multivariate regression Cox analysis shows gender, age, kidney function, cognitive function, operation were all risk factors that affect the 10-year mortality of patients after hip fracture. Female had a 0.687 time (95% CI, 0.516-0.915; P =0.010) HR than male. Patients receiving surgical operation had a 0.407 time (95%CI, 0.291-0.569; P<0.001) lower HR than the patients chose conservative therapy. With every increase of age, the mortality rate increased 1.073 times (95% CI, 1.049-1.097; P <0.001). Patients in group 3 had a 2.120 times higher HR than group 1(95% CI, 1.110-4.048; P = 0.023). Patients with mild cognitive function decline had a 1.949 times HR than people in normal cognitive function (95% CI, 1.163-3.265; P = 0.011). (Figure 6)

This is a study evaluating the short- and long-term mortality and risk factors affecting elderly patients with different glomerular filtration rate after hip fracture in China. It was revealed that after correcting the main clinical covariates, renal function was a risk factor associated with long-term mortality after hip fracture not short-term. Our analysis also confirmed that the mortality of hip fracture increased with age, decreased renal function, cognitive function and, at the same time, protective factors such as albumin level, female gender, and operation reduce the mortality odds.

With the kidney function declines, the mortality of elderly patients with different after hip fracture keep rising with years. The one-year mortality rate was 9.3%, 19.81%, 22.53%, five-year mortality rate was 21.87%, 55.86%, 78.87%, and ten-year mortality rate was 40.61%, 74.32%, 94.37% for each group with diffferent eGFR. Some studies confirmed that after adjusting for age, weight, low BMD, and a history of osteoporosis, renal function remained an important predictor of hip fracture prevalence[10].Hip fracture-related mortality is 2 times higher in elderly patients with grade III CKD[11]. Furthermore, a study proved that 44.7% of hip-fracture-related deaths among older people with eGFR < 45ml/min/1.73m² appeared to be attributable to the kidney dysfunction itself[12]. Similarly, this result was compatible with ours that with the decline of kidney function. Another study included the patients of CKD stages 3–5, part of whom were on renal replacement therapy, and follow up the risk of hip fracture and mortality in 5.5 years. Interestingly, the results showed that the risk of mortality after hip fracture increased only in CKD 4[13]. However, this was not completely consistent with our research, which may due to the fact that the average age of the study was 63.3 years old, while the population included in our study were over 65 years old, with an average age of 82.64 years old and age was a risk a factor in our study. In CKD patients, the prevalence of fracture in older adults (> 65 years) is about 23.4%-35.8%. Patients with normal eGFR aged 70–79 year-old and 80–89 year-old had a 1.2 times and 1.9 times higher risk of 30-day mortality than patient aged 60–69 year-old[14].Moreover, elderly patients had a higher risk of falling because of increased frailty, comorbidity and intense medication regimens[12]. CKD and aging exacerbated losses of cortical and trabecular micro-architecture and each resulted in thinner, more porous cortices and fewer and thinner trabeculae[15]. Thus, it can be predicted that the combination of aging and renal insufficiency may be linked to increase the mortality.

Interestingly, our study found that decreased renal function had little effect on one-year mortality in elderly patients with hip fracture, but increased 5-year and 10-year mortality. According to our study, the one-year mortality was 9.3% in the patients with eGFR > 90 ml/min/1.73m², lower than 19.81% in patients with eGFR60-89mL/min/1.73m² and 22.53% in patients with eGFR < 60 mL/min/1.73m². But there was no statistical difference. This was consistent with other studies that reported mortality rates between 8% and 36% during the first year[16]. However, another prospective study indentified the risk factors for one-year mortality in patients with hip fracture and found that impaired renal function had strong association with increased mortality at 1 year after hip fracture [17]. Compared with non-CKD patients, Patients with CKD had higher mortality at both 90 days and 1 year (hazard ratio 1.69 and 1.84, respectively).There was also a study confirmed that patients with chronic kidney disease (CKD) were more likely to develop AKI (30.8%) that those without it (17.2%, p = 0.018) after hip fracture[18]. But the mortality seemed to have little difference and eGFR was not the risk factor that affect one-year mortality in our study. Firstly, we didn’t exclude AKI from our inclusion and exclusion criteria, so there may be data bias. At the same time, the patients included in our study had not yet reached the diagnostic standards of CKD.While decreased kidney function was an important risk factor for the five to ten years’ mortality after hip fracture. Maybe high risk of mortality after hip fracture are attributable to both the old age and comorbidity.People with decreased eGFR were more likely to have complications after surgery, were prone to have renal osteodystrophy and easy to have systemic immune compromise[19]. A population-based study in Singapore found that patients with hip fracture, and pre-fracture CCI (Charlson Comorbidity Index) ≥ 4 had a higher risk of mortality (RR 3.29,95%CI (3.01–3.59)) [20]. In elderly patient with hip fracture, cardiac function was an independent factor of mortality. A study assessed the early and late mortality after hip fracture between heart failure (HF) and non-HF showed that the short- and long-term mortality were higher in patients diagnosed with HF and in the subgroup analysis, moderate-to-severe HF was 4 times higher than mild HF[20]. Our study also illustrated that people with decreased renal function often had worse cardiac function. From our study, patients with lower eGFR had worse cardiac function. The cardiac function of 68% and 24% patients with eGFR between 60 and 89mL/min/1.73m² and eGFR < 60 mL/min/1.73m² were NYHA II-III. Another comorbidity was pulmonary disease. Study shown pulmonary disease account for approximately 35% of the poor prognoses of CKD patients and the incidence of septic shock among elderly CKD patients has been rising, especially in patient after hip fracture[21, 22]. Another possible mechanism put forward for the association between renal impairment and the increasing long-term mortality after hip fracture was as follows: as time goes by and the progression of CKD, abnormalities of mineral metabolism occurred. Abnormal calcium-phosphate metabolism, decreased levels of circulating calcitriol and increased levels of parathyroid hormone (PTH), together result in renal osteodystrophy[23]. Compared with baseline, bone changes annually in patients with CKD 2-5D. With the extension of follow-up, the cortical area (-2.9%,95% CI (-3.7, -2.2)), density (-1.3%,95%CI (-1.6, -0.6)) and thickness (-2.8%,95%CI (-3.6,-1.9)) were significantly declined[24, 25]. Thus, it can be suspected that in both macro and micro perspectives, CKD could reduce bone quality to exacerbate the incidence of fracture and death.

In our study, receiving surgical treatment was a major protective factor that affects the short-term and long-term mortality of patients with hip fracture. The location of the fracture determines different treatment methods and surgical methods. Although recently studies demonstrated that for most individuals with hip fracture, the most common surgical method was internal fixation (55.8%), whereas 29.2%-31.6% of individuals underwent partial hip replacement, and 2.4% of individuals received a total hip replacement. Only a small percentage of patients were treated conservatively or died within 3 days of the hip fracture. While over the 14 years of study, due to the improvements in anesthesia, surgical techniques and early rehabilitation, the outcomes after hip fracture were greatly improved[26]. Those people who didn’t get surgical treatment usually have high risk of death, suggesting that surgery is an effective way to reduce mortality. Excessive blood loss, pneumonia, cardiovascular disease, pressure sores may contribute to the death of patients receiving conservative treatment[27]. These results were compatible with ours that early and effective surgical treatment can greatly improve survival after hip fracture.

Some limitations of our study needed to be mentioned. First of all, we were unable to dynamically follow up the changes in patients’ renal function during the follow-up process. And we didn’t record the causes of renal dysfunction, such as nephrotic syndrome, diabetic nephropathy, etc. Secondly, Due to the limitation of experimental conditions, not everyone included in our study had been tested for bone metabolism markers like parathyroid hormone, 25-hydroxyvitamin D with hip fracture. Thirdly, we didn’t record the bone mineral density and geriatric composite assessments, which have great effect on the patients after hip fracture, and we were unable to compare their interaction with decreased renal function. Finally, we didn’t take the effects of anti-osteoporosis drugs after fractures into consideration.

In conclusion, our study found that renal function seems to have little effect on short term mortality of Chinese elderly patients after hip fracture, but was an important risk factor affecting the medium to long-term mortality. For patients with decreased eGFR, fully evaluating the status of patients and choosing appropriate surgical method as soon as possible after fracture can greatly reduce the risk of death and ensure better survival in the elderly.

CKD: Chronic kidney disease

CKD-MBD: Chronic kidney disease-mineral and bone disorder

eGFR: Estimated glomerular filtration rate

Hb: Hemoglobin

ALB: Albumin

BG: Blood glucose

BUN: Blood urea nitrogen

Scr: Serum creatinine

BMI: Body mass index

CKD-EPI: Chronic Kidney Disease Epidemiology Collaboration

CRF: Case Report Form

AKI: Acute kidney injury

HF: Heart failure

Acknowledgments

None

Authors’ contributions

WH, ZBY designed the whole experiment. YSW, YQF, SBZ collected the data and follow up the patients. YSW analyzed the data and wrote the manuscript. WH revised the article. All authors read and approved the final manuscript.

Funding

Not applicable

Availability of data and materials

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Ethics approval and consent to participate

Our study was approved by the ethics committee of Huadong hospital affiliated to Fudan University and the protocols were carried out in accordance with the ethical principles for medical research involving human subjects. Written informed consents were obtained from all subjects.

Competing interests

The authors declare that they have no competing interests.

Consent for publication

Not applicable

Author details

1 Department of Nephrology, Huadong Hospital affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai 200040, P.R. China.

2 Department of Nephrology, Shanghai East Hospital, Tongji University School of Medicine, No.1800 Yuntai Road, Shanghai 200123, P.R. China.

3 Department of Health Management, Huadong Hospital affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai 200040, P.R. China.

4 Department of Orthopedics, Huadong Hospital affiliated to Fudan University, No. 221 West Yan'an Road, Shanghai 200040, P.R. China.

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Table1 Baseline characteristics stratified by eGFR

Variable name	Overall (n=325)	Group 1 (n=32)	Group 2 (n=222)	Group 3 (n=71)	P value
Age (year)	82.64±6.41	75.69±6.06	82.75±5.81	85.45±6.07	<0.001^abc
Male (%)	86 (26.5%)	0 (0.0%)	68 (30.6%)	18(25.4%)	<0.001^ac
Body weight (kg)	56.37±8.00	55.80±8.12	56.29±7.81	56.87±8.60	0.799
Height (cm)	159.77±10.51	159.33±4.47	159.75±12.15	160.06±5.98	0.947
BMI (kg/m²)	22.84±3.77	23.62±3.49	22.64±3.89	23.12±3.43	0.303
Hb (g/L)	113.80±19.00	117.52±14.27	115.38±18.77	107.19±20.25	0.003^bc
Alb (g/L)	36.04±4.56	37.25±3.54	36.12±4.93	35.23±3.58	0.101
ALT(U/L)	14.00 (11.00~19.00)	16.00 (13.00~19.75)	14.00 (11.00~19.25)	14.00 11.00~19.25)	0.413
Length of stay (day)	19.11±9.36	23.72±14.79	18.45±7.91	19.08±10.00	0.012^ac
Expense	4.67±2.36	5.03±2.17	4.55±1.97	4.86±3.34	0.416
Survive time(year)	4.75±3.53	7.49±3.24	4.87±3.57	3.16±2.56	<0.001^abc
Co-morbidity
HBP	143(44.0%)	13(40.6%)	92(41.4%)	38(53.5%)	0.187
T2DM	67 (20.6%)	6(18.8%)	45(20.3%)	16(22.5%)	0.885
CHD	46(14.2%)	2(6.3%)	29(13.1%)	15(21.1%)	0.105
COPD	26(8.0%)	1(3.1%)	18(8.1%)	7(9.9%)	0.583
Fracture type					0.364
Femoral head	2 (0.6%)	0 (0.0%)	1 (0.5%)	1 (1.4%)
Femoral neck	134 (41.2%)	16(50.0%)	95(42.8%)	23 (32.4%)
Intertrochanteric	189 (58.2%)	16(50.0%)	126(56.8%)	47 (66.2%)
Cognitive function					0.415
Mildly decreased	304 (93.5%)	31 (96.9%)	207(93.2%)	66 (93.0%)
Moderately decreased	18 (5.5%)	1 (3.1%)	14 (6.3%)	3(4.2%)
Severely decreased	3 (0.9%)	0 (0.0%)	1 (0.5%)	2 (2.8%)
Cardiac function					<0.001
NYHA I	38 (11.7%)	10 (31.3%)	26 (11.7%)	2 (2.8%)
NYHA II	249 (76.6%)	21(65.6%)	171 (77.0%)	57 (80/3%)
NYHA III	37 (11.46%)	1 (3.1%)	24 (10.8%)	12 (16.9%)
NYHA IV	1 (0.3%)	0 (0.0%)	1 (0.5%)	0 (0.0%)
Operation					0.510
Yes	277 (85.2%)	29(90.6%)	190 (85.6%)	58 (81.7%)
No	48 (14.8%)	3(9.4%)	32(14.4%)	13 (18.3%)

_{Normally distributed}_{variables are presented as mean ± SD. For}_{non-normally distributed}_{data such as ALT, medians and the 25th and 75th percentiles are shown. Categorical variables are presented as percentages. Bold indicates statistical significance (P value <0.05).}^a_{P<0.05 Group2 vs. Group1}_；^b_{P<0.05 Group2 vs. Group3}_；^c_{P<0.05 Group1 vs. Group3}_；

Table 2 Baseline characteristics stratified by different eGFR in surgical patients

	Overall (n=309)	Group 1 (n=31)	Group 2 (n=211)	Group 3 (n=67)	P value
Surgery type					0.016^c
Internal fixation	179(57.9%)	15(48.4%)	117(55.5%)	47(70.1%)
Hemi hip replacement	107(34.6%)	10(32.3% )	78(37.0%)	19(28.4%)
Total hip replacement	23(7.4%)	6(19.4%)	16(7.6%)	1(1.5%)
Anesthesia Type					0.426
General anesthesia	59(19.1%)	9(29.0%)	42(19.9%)	8 (11.9%)
Epidural anesthesia	11(3.6%)	1(3.2%)	7(3.3%)	3(4.5%)
Lumbar anesthesia	238(77.0%)	21(67.7%)	161(76.3%)	56(83.6%)
Combined anesthesia	1(0.3%)	0(0.0%)	1(0.5%)	0(0.0%)
Perioperative blood transfusion					0.013^bc
Yes	88(28.5%)	5(16.1%)	55(26.1%)	28(41.8%)
No	221(71.5%)	26(83.9%)	156(73.9%)	39(58.2%)

_{Bold indicates statistical significance (P value <0.05).}^a_{P<0.05 Group2 vs. Group1}_；^b_{P<0.05 Group2 vs. Group3}_；^c_{P<0.05 Group1 vs. Group3}_；

Table3 Cumulative mortality rates after hip fracture stratified by eGFR

		Group 1 (n=32)	Group 2 (n=222)	Group 3 (n=71)	Total (n=325)	χ²	P value
One-year	Death	3(9.30%)	44(19.81%)	16(22.53%)	63(19.38%)	2.455	0.294
	Alive	29(90.7%)	178(80.19%)	56(77.47%)	262(80.92%)	2.455	0.294
Five-year	Death	7(21.87%)	124(55.86%)	56(78.87%)	187(57.54%)	30.144	<0.001^abc
	Alive	25(78.13%)	98(44.14%)	15(21.13%)	138(42.46%)	30.144	<0.001^abc
Ten-year	Death	13(40.61%)	165(74.32%)	67(94.37%)	245(75.38%)	34.760	<0.001^abc
	Alive	19(59.39%)	57(25.68%)	4(5.63%)	80(24.62%)	34.760	<0.001^abc

_{All p-values were significant at P < 0.05}_{. Bold indicates statistical significance (P value <0.05).}^a_{P<0.05 Group2 vs. Group1}_；^b_{P<0.05 Group2 vs. Group3}_；^c_{P<0.05 Group1 vs. Group3}_；

No competing interests reported.

The risk factors and mortality in elderly patients with different glomerular filtration rate after hip fracture

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