Basic characteristics of the subjects
A total of 10,753 subjects (5258 males and 5495 females) were included in this study. Among all the subjects, 996 had had kidney stones, and 9757 had no history of kidney stones. The overall prevalence rate (95% CI) was 9.3% (8.7%-9.8%). Table 1 provides the general information for individuals in the kidney stone group and the non-kidney stone group. Sex, age, BMI, history of hypertension, history of diabetes, ALB, and UA significantly differed between the kidney stone group and the non-kidney stone group. In contrast, history of smoking, history of drinking, and ALT did not significantly differ between these groups. The percentage of males, percentage of individuals with a history of hypertension, percentage of individuals with a history of diabetes, percentage of individuals with an abnormal BMI, and UA level were significantly higher in the kidney stone group than in the non-kidney stone group. However, the ALB level was significantly lower in the kidney stone group than in the non-kidney stone group.
Table 1 General characteristics of study subjects
variable
|
non-stone group
(n=9757)
|
stone group
(n=996)
|
P level
|
ALB (g/L)
|
43.00
(41.00-45.00)
|
42.00
(40.00-44.00)
|
<0.0001
|
ALT (U/L)
|
21.00
(16.00-28.00)
|
22.00
(17.00-29.00)
|
0.4873
|
UA (μmol/L)
|
321.20
(267.70-374.70)
|
333.10
(273.60-392.60)
|
0.0032
|
Age
|
46.00
(32.00-59.00)
|
53.00
(42.00-65.00)
|
<0.0001
|
Alcohol history
|
|
|
0.2432
|
No
|
2581(22.46%)
|
271(24.50%)
|
|
Yes
|
6695(77.54%)
|
682(75.50%)
|
|
BMI
|
|
|
<0.0001
|
18.5-24.99
|
2642(29.58%)
|
187(19.49%)
|
|
<18.5 or >24.99
|
6634(70.42%)
|
766(80.51%)
|
|
Hypertension history
|
|
|
<0.0001
|
No
|
6088(69.36%)
|
488(54.55%)
|
|
Yes
|
3188(30.64%)
|
465(45.45%)
|
|
Diabetes history
|
|
|
<0.0001
|
No
|
8272(92.16%)
|
770(85.15%)
|
|
Yes
|
1004(7.84%)
|
183(14.85%)
|
|
Sex
|
|
|
0.0007
|
Female
|
4827(51.83%)
|
424(45.53%)
|
|
Male
|
4449(48.17%)
|
529(54.47%)
|
|
Smoking history
|
|
|
0.1544
|
No
|
5190(55.62%)
|
490(52.08%)
|
|
Yes
|
4086(44.38%)
|
463(47.92%)
|
|
Abbreviations. ALB, albumin; ALT, alanine transaminase; UA, uric acid. The data are presented as the mean ± standard deviation or median (interquartile range) and numbers (percentage) as appropriate.
Comparison of the blood lipid level between the kidney stone group and the non-kidney stone group
Table 2 provides the blood lipid level results for the kidney stone group and the non-kidney stone group. According to the nonparametric test results, the TG, HDL-C, and TC/HDL-C levels significantly differed between the kidney stone group and the non-kidney stone group. In contrast, the TC and LDL-C levels did not significantly differ between these groups. Compared with the non-kidney stone group, the kidney stone group had significantly higher TG and TC/HDL-C levels and a significantly lower HDL-C level. TC, TG, LDL-C, and HDL-C data were further divided into normal and abnormal blood lipid categories based on reference level ranges and then subjected to the chi-square test. The percentage of individuals with abnormal TG or HDL-C levels significantly differed between the two groups. Specifically, the levels of both markers were significantly higher in the kidney stone group than in the non-kidney stone group. Conversely, the percentages of individuals with abnormal TC and LDL-C levels did not significantly differ between the two groups.
Table 2 Comparison of blood lipid levels in all study participants
variable
|
non-stone group
(n=9757)
|
stone group
(n=996)
|
P level
|
TC (mmol/L)
|
4.89
(4.24-5.61)
|
4.94
(4.29-5.61)
|
0.5683
|
LDL-C (mmol/L)
|
2.87
(2.33-3.52)
|
2.92
(2.40-3.52)
|
0.9004
|
TG (mmol/L)
|
1.13
(0.78-1.63)
|
1.21
(0.86-1.85)
|
0.0008
|
HDL-C (mmol/L)
|
1.34
(1.11-1.63)
|
1.24
(1.06-1.53)
|
<0.0001
|
TC/HDL-C
|
3.57
(2.86-4.42)
|
3.84
(3.08-4.67)
|
0.0001
|
HDL-C (mmol/L)
|
|
|
0.0031
|
≥1.03 mmol/L
|
7833(84.41%)
|
757(78.95%)
|
|
<1.03 mmol/L
|
1443(15.59%)
|
196(21.05%)
|
|
TC (mmol/L)
|
|
|
0.8103
|
<5.18 mmol/L
|
5653(61.16%)
|
593(61.67%)
|
|
≥5.18 mmol/L
|
3623(38.84%)
|
360(38.33%)
|
|
LDL-C (mmol/L)
|
|
|
0.7282
|
<3.37 mmol/L
|
6512(70.34%)
|
671(69.56%)
|
|
≥3.37 mmol/L
|
2764(29.66%)
|
282(30.44%)
|
|
TG (mmol/L)
|
|
|
0.0001
|
<1.7 mmol/L
|
7129(77.23%)
|
665(69.88%)
|
|
≥1.7 mmol/L
|
2147(22.77%)
|
288(30.12%)
|
|
Abbreviations. TC, total cholesterol; TG, triglyceride; LDL-C, low-density lipoprotein cholesterin; HDL-C, high-density lipoprotein cholesterol; TC/HDL-C, the ratio of TC to HDL-C. The data are presented as the mean ± standard deviation or median (interquartile range) and numbers (percentage) as appropriate.
Relationship between dyslipidaemia and risk of kidney stones
First, a univariate weighted logistic regression analysis was performed using the presence/absence of TG abnormalities, presence/absence of HDL-C abnormalities, and quartile grouping of TC/HDL-C as independent variables and the presence/absence of kidney stones as the dependent variable. The results indicated that abnormal TG, abnormal HDL-C, and the Q2 and Q4 groups of TC/HDL-C were correlated with a higher risk of kidney stones. Subsequently, confounding factors were included in the model, and multivariate weighted logistic regression analysis was performed. After adjusting for sex, age, and BMI abnormality in model 1, abnormal TG, abnormal HDL-C, and the TC/HDL-C levels of the Q2 and Q4 groups remained correlated with a higher risk of kidney stones. Model 2 was then constructed after further including ALB, UA, a history of hypertension, and a history of diabetes. Abnormal HDL-C levels did not correlate with the risk of kidney stones. In contrast, abnormal TG and Q2 and Q4 TC/HDL-C levels remained significantly correlated with a higher risk of kidney stones (the results are shown in Table 3). Figure 2 shows the multivariate analysis and best-fitting smooth curves between various blood lipid levels and prevalence rates for kidney stones. The results revealed that the prevalence rates for kidney stones continued to increase with an increase in TG and TC/HDL-C levels and a decline in HDL-C levels.
Table 3 Association between dyslipidaemia and the risk of kidney stones in NHANES 2007-2016.
|
Stone prevalence, n (%)
|
Univariate modela
|
Multivariable model 1b
|
Multivariable model 2c
|
OR (95% CI)
|
P level
|
OR (95% CI)
|
P level
|
OR (95% CI)
|
P level
|
TG
|
|
|
|
|
|
|
|
<1.7 mmol/L
|
665(8.76%)
|
reference
|
|
reference
|
|
reference
|
|
≥1.7 mmol/L
|
288(12.30%)
|
1.461(1.209-1.766)
|
<0.001
|
1.253(1.031-1.524)
|
0.027
|
1.241(1.014-1.519)
|
0.040
|
HDL-C
|
|
|
|
|
|
|
|
≥1.03 mmol/L
|
757(9.03%)
|
reference
|
|
reference
|
|
reference
|
|
<1.03 mmol/L
|
196(12.52%)
|
1.443(1.130-1.841)
|
0.004
|
1.371(1.060-1.774)
|
0.019
|
1.307(0.997-1.714)
|
0.057
|
TC/HDL-C
|
|
|
|
|
|
|
|
≤2.88
|
185(6.76%)
|
reference
|
|
reference
|
|
reference
|
|
2.89-3.57
|
245(9.85%)
|
1.509(1.161.953)
|
0.003
|
1.367(1.046-1.788)
|
0.025
|
1.371(1.051-1.790)
|
0.023
|
3.58
|
243(9.92%)
|
1.520(1.125-2.053)
|
0.008
|
1.352(0.993-1.841)
|
0.060
|
1.374(1.016-1.860)
|
0.043
|
>4.47
|
280(11.86%)
|
1.857(1.439-2.397)
|
<0.001
|
1.600(1.209-2.116)
|
0.002
|
1.643(1.250-2.161)
|
0.001
|
a: Univariate weighted logistic regression analysis
b: Model 1 was adjusted for sex, age, BMI
c: Model 2 was adjusted for sex, age, BMI, ALB, UA, hypertension, diabetes
Abbreviations. TC, total cholesterol; TG, triglyceride; LDL-C, low-density lipoprotein cholesterin; HDL-C, high-density lipoprotein cholesterol; TC/HDL-C, the ratio of TC to HDL-C; OR, odds ratio; 95% CI, 95% confidence interval. The cutoff levels of quartiles were ≤ 2.88, 2.89-3.57, 3.58-4.47 and > 4.47 of TC/HDL-C.
The relationship between dyslipidaemia and kidney stone risk after stratification by age group
After stratifying the overall data by age group (20-40, 41-60, and 61-80 years), univariate and multivariate weighted logistic regression analyses were performed. The results are shown as forest plots in Figure 3. The specific findings were as follows.
(1) The univariate weighted logistic regression analysis indicated that in the population aged 20-40 years, TG and HDL-C abnormalities and Q4 TC/HDL-C levels were significantly correlated with a higher risk of kidney stones. The multivariate weighted logistic regression analysis produced the same result after adjusting for sex and the presence/absence of BMI abnormalities in Model 1 and further adjusting for ALB, UA, history of hypertension, and history of diabetes in Model 2.
(2) For the population aged 41-60 years, the univariate weighted logistic regression analysis indicated that the Q4 TC/HDL-C level was significantly correlated with a higher risk of kidney stones. However, TG and HDL-C abnormalities were not significantly correlated with the risk of kidney stones. In contrast, in the multivariate weighted logistic regression analysis, no variables were significantly correlated with the risk of kidney stones in Model 1 and Model 2.
(3) The univariate weighted logistic regression analysis indicated that in the population aged 61-80 years, HDL-C abnormalities and Q4 TC/HDL-C levels were significantly correlated with a higher risk of kidney stones. TG abnormalities were not significantly correlated with the risk of kidney stones. Again, in the multivariate weighted logistic regression analysis, no variables were significantly correlated with the risk of kidney stones in Model 1 and Model 2.
The relationship between dyslipidaemia and kidney stone risk after stratification by sex
Subsequently, we grouped the data by sex and performed univariate and multivariate weighted logistic regression analyses. The results are shown as forest plots in Figure 4. The specific findings were as follows.
(1) In the male subgroup, univariate weighted logistic regression analysis indicated that TG and HDL-C abnormalities and Q4 TC/HDL-C levels were significantly correlated with a higher risk of kidney stones. Multivariate weighted logistic regression analysis indicated that in Model 1, HDL-C abnormality and Q3 and Q4 TC/HDL-C levels were significantly correlated with a higher risk of kidney stones. In contrast, TG abnormalities did not significantly correlate with the risk of kidney stones.
(2) In the female subgroup, univariate weighted logistic regression analysis indicated that TG abnormalities and Q2, Q3, and Q4 TC/HDL-C levels were significantly correlated with a higher risk of kidney stones. HDL-C abnormalities did not significantly correlate with kidney stone risk. Multivariate weighted logistic regression analysis indicated that the Q4 TC/HDL-C level was significantly correlated with a higher risk of kidney stones in both Model 1 and Model 2. TG and HDL-C abnormalities were not significantly correlated with the risk of kidney stones.
The relationship between dyslipidaemia and kidney stone risk after stratification by BMI degree
Finally, we stratified the data based on the presence or absence of BMI abnormalities in the research subjects and then performed univariate and multivariate weighted logistic regression analyses. The results are shown as forest plots in Figure 5. The specific findings were as follows.
(1) In the subgroup with normal BMI, neither univariate nor multivariate weighted logistic regression analysis identified any variables that were significantly correlated with the risk of kidney stones.
(2) In the subgroup with abnormal BMI, univariate weighted logistic regression analysis indicated that abnormal TG, abnormal HDL-C, and Q3 and Q4 TC/HDL-C levels were correlated with a higher risk of kidney stones. In the multivariate weighted logistic regression analysis, Model 1 generated the same results. However, for Model 2, HDL-C abnormalities did not significantly correlate with the risk of kidney stones.