The relation between estimated glomerular filtration rate (eGFR) and coffee consumption in the Japanese

doi:10.4236/health.2011.39093

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Vol.3, No.9, 549-552 (2011)

doi:10.4236/health.2011.39093

Health

The relation between estimated glomerular filtration rate

(eGFR) and coffee consumption in the Japanese

Nobuyuki Miyatake1*, Kenichi Shikata2,3, Hirofumi Makino3, Takeyuki Numata4

1Department of Hygiene, Faculty of Medicine, Kagawa University, Kagawa, Japan;

*Corresponding Author: [email protected]

2Center for Innovative Medicine, Okayama University Hospital, Okayama, Japan;

3Department of Medicine and Clinical Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical

Sciences, Okayama, Japan;

4Okayama Southern Institute of Health, Okayama Health Foundation, Okayama, Japan.

Received August 10th, 2011; revised August 26th, 2011; accepted September 5th, 2011.

ABSTRACT

We investigated the link between estimated

glomerular filtration rate (eGFR) and coffee

consumption in Japanese. We used data of 376

men and 794 women who were not taking any

medications, aged 20 - 78 years, in this cross-

sectional investigation study. eGFR was calcu-

lated using serum creatinine (Cr), age and sex.

Habitual coffee consumption was defined as

drinking one or more cups of coffee per day. Two

hundred thirty three men (62.0%) and 400

women (50.4%) were subjects with habitual cof-

fee consumption (coffee consumption 1 cup/

day ≥). eGFR was negatively correlated with age

(men: r = –0.533, women: r = –624). eGFR in

subjects with coffee consumers was not sig-

nificantly different from that in subjects without

coffee consumers after adjusting for age in both

sexes (men: p = 0.1375, women: p = 0.2069).

Among Japanese not taking medications, coffee

consumption was not associated with eGFR in

the Jap anese population.

Keywords: Estimated Glomerular Filtration Rate

(eGFR); Coffee Consumption; Creatinine;

Japanese

1. INTRODUCTION

Coffee is one of the most common frequently con-

sumed beverages and 10.6 coffee cups per week are re-

ported to be consumed [1] and about 50% of Japanese

drinks coffee daily [2]. Some studies showed that habit-

ual coffee consumption may improve insulin resistance

and abdominal glucose metabolism [3-5]. However, To-

fovic et al. [6] have reported that prolonged consump-

tion of caffeine has adverse effects on renal function, in

high-renin hypertension.

Chronic kidney disease (CKD) has become a public

health challenge and is a common disorder [7]. For ex-

ample, about 20% of adults have CKD, which is defined

as kidney damage or a glomerular filtration rate (GFR) <

60 ml/min/1.73 m2 for at least three months regardless of

cause [8]. We have also previously reported in a cross-

sectional study that the estimated glomerular filtration

rate (eGFR) [9] in men with abdominal obesity and in

women with hypertension was significantly lower than

that in subjects without these components of metabolic

syndrome [10]. Therefore, the effect of coffee consump-

tion on renal function may be required and it still re-

mains to be investigated in Japanese.

In this study, we investigated renal function evaluated

by eGFR in Japanese and evaluated the clinical impact

of coffee consumption on eGFR in subjects not taking

medications.

2. SUBJECTS AND METHODS

2.1. Subjects

We used all data on 1170 Japanese (376 men and 794

women) aged 20-78 years in a cross-sectional study. All

subjects met the following criteria: 1) they had wanted to

change their lifestyle i.e. diet and exercise habits, and

had received an annual health checkup from April 2006

to December 2010 at Okayama Southern Institute of

Health; 2) they had received creatinine (Cr), anthropom-

etric measurements and evaluation of coffee consump-

tion as part of their annual health checkups; and 3) they

provided informed consent (Table 1).

The study was approved by the Ethics Committee of

Okayama Health Foundation.

N. Miyatake et al. / Health 3 (2011) 549-552

550

Table 1. Clinical profiles of enrolled subjects.

Men Women

Mean ± SD Minimum Maximum Mean ± SD Minimum Maximum

Number of subjects 376 794

Age 42.7 ± 13.2 20 74 40.6 ± 14.5 20 78

Height (cm) 170.3 ± 6.1 143.7 186.7 157.4 ± 5.3 140.5 172.9

Body weight (kg) 71.3 ± 11.7 42.0 120.3 54.4 ± 8.5 29.3 113.9

Body mass index (kg/m2) 24.6 ± 3.6 14.6 41.8 22.0 ± 3.3 14.1 44.9

Abdominal circumference (cm) 85.3 ± 10.1 60.5 122.0 75.7 ± 9.8 55.1 120.0

Hip circumference (cm) 95.7 ± 8.4 74.5 193.4 92.0 ± 7.0 70.0 196.5

Systolic blood pressure (mmHg) 127.4 ± 13.894.0 191.0 114.7 ± 15.685.0 192.0

Diastolic blood pressure (mmHg) 75.9 ± 10.9 50.0 112.0 67.0 ± 10.9 40.0 111.0

Creatinine (mg/dl) 0.84 ± 0.12 0.51 1.34 0.62 ± 0.09 0.29 1.00

eGFR (ml/min/1.73 m2) 83.2 ± 15.5 41.0 139.7 88.8 ± 18.2 42.5 172.9

Coffee consumption (cup/week) 9.5 ± 8.5 0 40 7.5 ± 7.9 0 50

2.2. Anthropometric Measurement s

The anthropometric parameters were evaluated by us-

ing the following respective parameters such as height,

body weight, body mass index (BMI), abdominal cir-

cumference, and hip circumference. BMI was calculated

by weight/[height]2 (kg/m2). The abdominal circumfer-

ence was measured at the umbilical level and the hip was

measured at the widest circumference over the tro-

chanter in standing subjects after normal expiration [11].

2.3. Blood Pressure Measurements

Each participant’s blood pressure was measured after

resting at least 15 minutes in the sitting position.

2.4. Blood Sampling and Assays

The level of Cr was measured with an automated bio-

chemical analyzer (model 7700; HITACHI, Tokyo, Ja-

pan) and Accuras Auto CRE (Shino-Test Corporation,

Tokyo, Japan) at the Okayama Southern Institute of

Health, Okayama Health Foundation. eGFR was calcu-

lated using the following equation: eGFR (ml/min/1.73

m2) = 194 × Cr–1.094 × Age–0.287 (for men) and eGFR (ml/

min/1.73 m2) = 194 × Cr–1.094× Age–0.287 × 0.739 (for

women) [9]. Reduced eGFR was defined as an eGFR <

60 ml/min/1.73 m2.

2.5. Coffee Consumption

Subjects were asked how many cups of coffee per week.

They were dichotomized into coffee consumers who

drink one or more cups of coffee per day, and non-coffee

consumers who seldom drink coffee. The way of drink-

ing was not asked.

2.6. Statistical Analysis

Data are expressed as means ± standard deviation (SD)

values. A comparison of parameters between the two

groups was made using the unpaired t-test and covari-

ance analysis. Simple correlation analysis was per-

formed as well to test for the significance of the linear

relationship among continuous variables: p < 0.05 was

considered statistically significant.

3. RESULTS

The mean eGFR was 83.2 ± 15.5 ml/min/1.73 m2 in

men and 88.8 ± 18.2 ml/min/1.73 m2 in women (Table

1). The mean coffee consumption was 9.5 ± 8.5 cups/

week/person in men and 7.5 ± 7.9 cups/week/person. A

diagnosis of reduced eGFR was made for 19 men (5.1%)

and 27 women (3.4%). eGFR was negatively correlated

with age in either sex (Figure 1).

We clarified the prevalence of subjects with coffee

consumers among subjects who were not taking without

medications (Table 2). Among the 1,170 Japanese sub-

jects, 233 men (62.0%) and 400 women (50.4%) were

coffee consumers (coffee consumption 1 cup/day ≥). The

prevalence of coffee consumers was the highest in 50’s

in men and 70’s in women.

In subjects not taking medications, we also compared

eGFR levels between the groups with and without coffee

N. Miyatake et al. / Health 3 (2011) 549-552

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consumers of the Japanese (Table 3). To avoid the in-

fluence of age, we used age as a covariate and compared

eGFR between Japanese with and without coffee con-

sumers using covariance analysis. The significant dif-

ference of eGFR was not noted between subjects with

and without coffee consumers, even after adjusting for

age.

4. DISCUSSION

We firstly evaluated the link between eGFR using

newly developed in Japan and coffee consumption in

Japanese without taking any medications. The difference

of eGFR was not noted between subjects with and with-

out coffee consumers.

Figure 1. Simple correlation analysis between estimated glomerular filtration rate (eGFR) and age.

Table 2. Coffee consumption as classified by age groups.

20 - 29 30 - 39 40 - 49 50 - 59 60 - 69 70- Total

Men

Coffee consumption 1 cup/day < 44 (65.7) 37 (35.9) 32 (37.6) 16 (21.6) 12 (30.0) 2 (28.6) 143 (38.0)

Coffee consumption 1 cup/day ≥ 23 (34.3) 66 (64.1) 53 (62.4) 58 (78.4) 28 (70.0) 5 (71.4) 233 (62.0)

Men

Coffee consumption 1 cup/day < 206 (85.4) 73 (48.0) 37 (23.0) 45 (32.4) 29 (33.7) 4 (26.7) 394 (49.6)

Coffee consumption 1 cup/day ≥ 35 (14.5) 79 (52.0) 124 (77.0) 94 (67.6) 57 (66.3) 11 (73.3) 400 (50.4)

Number of subjects (%).

Table 3. Comparison of eGFR between subjects as classified by coffee consumption.

Coffee consumption 1 cup/day <Coffee consumption 1 cup/day ≥p p (After adjusting for age)

Men

Number of subjects 143 233

Age 38.8 ± 13.7 45.1 ± 12.4 <0.0001

eGFR (ml/min/1.73 m2) 86.5 ± 16.5 81.1 ± 14.4 0.0009 0.1375

Women

Number of subjects 394 400

Age 34.5 ± 14.3 46.6 ± 12.1 <0.0001

eGFR (ml/min/1.73 m2) 94.1 ± 19.0 83.6 ± 15.9 <0.0001 0.2069

ean ± SD.

N. Miyatake et al. / Health 3 (2011) 549-552

552

Iso et al. [2] reported that consumption of green tea,

coffee, and total caffeine was associated with a risk for

type 2 diabetes in 17,413 subjects with 5-year follow-up.

Multivariable odds ratio for diabetes among participants

who frequently drank coffee (3 cups of coffee per day ≥)

was 0.58, respectively, compared with those who drank

less than 1 cup per week. According to the link between

habitual coffee consumption and eGFR in Japanese,

Nakajima et al. [12] reported that eGFR in coffee con-

sumers (n = 182) was significantly higher than that in

non-coffee consumers (n = 160), which was not attenu-

ated even after adjustment for age, sex and considerable

factors. Kotani et al. [13] also reported that coffee

drinkers had higher eGFR values than non-coffee drink-

ers in 114 Japanese. The difference remained significant,

independently of clinical variables. However, in this

study, we could not found the significant difference of

eGFR between subjects with and without habitual coffee

consumption. Compared the previous studies, the age

enrolled in this study was younger. In addition, the age

in subjects with habitual coffee consumption was sig-

nificantly higher than that in subjects without in this

study. Enrolled subjects in this study were taking no

medications, suggesting apparently healthy subjects.

Prolonged caffeine consumption has adverse effects on

renal function in rats [6]. Therefore, the results may not

be similar to previous reports.

Potential limitations remain in this study. First, our

study was a cross sectional and not a longitudinal study.

Second, the 1170 subjects, all of whom wanted to

change their lifestyle, underwent measurements for this

study: they were therefore more health-conscious than

the average person. Second, we could not clarify the

mechanism the link between eGFR and coffee consump-

tion. Third, the coffee consumption was reported to be

10.6 cups/week/person in 2008, and it is the highest be-

tween 40 and 59 (men: 13.5 cups/week/person, women:

14.2 cups/week/person) in Japanese by All Japan Coffee

Association [1]. The coffee consumption was gradually

increasing [1]. In this study, the mean of the coffee con-

sumption was lower than that in the previous report.

Further prospective studies are needed in Japanese sub-

jects using the new Japanese criteria.

5. ACKNOWLEDGEMENTS

This research was supported in part by Research Grants from the

Ministry of Health, Labor, and Welfare, Japan.

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