Phillips P1, Baldock K2, Chittleborough C2, Taylor A3, and the North West Adelaide Health Study Team

1 Endocrinology, The Queen Elizabeth Hospital, Woodville, South Australia, Australia 2 Diabetes Clearing House, Population Research and Outcome Studies Unit, Department of Health, Adelaide, South Australia, Australia3 Population Research and Outcome Studies Unit, Department of Health, Adelaide, South Australia, Australia

NNorth orth WWest

AAdelaide

HHealthealth SStudytudy

NNorth orth WWest

AAdelaide

HHealthealth SStudytudy

Diabetes is associated with an increased risk of kidney disease.The North West Adelaide Health Study, a biomedical cohort study of a random representative sample of people living in the north western suburbs of Adelaide, was used to determine whether renal function is impaired before development of diabetes.

All households within the north west region of Adelaide, with a telephone connected and the telephone number listed in the Electronic White Pages were eligible for selection in the North West Adelaide Health Study. Within each household, the person who had their birthday last and was aged 18 years or older, was selected for interview and invited to attend the study clinic. Of those who were interviewed, 4060 attended the clinic in Stage 1 (2000-2003), resulting in a clinic participation rate of 69%. Of the original cohort at Stage 1, 94.3% were contacted at Stage 2 (2004-2006), with diabetes status at follow-up obtained for 78.3% (n=3180) of original participants. Data were weighted by age, sex, area of residence and probability of selection in the household to ensure that the sample was representative.

Data presented here are from fasting blood, including fasting plasma glucose (FPG), and urine samples collected at Stage 2.

METHODS

INTRODUCTION

RESULTS

Renal function by stage of diabetes progression: impairment begins before diabetes develops

CONCLUSIONS

These data provide evidence that renal function, particularly asmeasured by microalbuminuria, is impaired among people with IFG. This indicates that activities focused on prevention of microalbuminuria should occur before diabetes develops.

Box 1. Definitions of microalbuminuria and chronic kidney disease

Microalbuminuria:

Chronic kidney disease:

For males,eGFR=186.3((serum creatinine/88.4)^(-1.154))*age^(-0.203)

For females, this equation is multiplied by 0.742.

estimated glomerular filtration rate (eGFR)* < 60 ml/min/1.73m2

Urinary albuminun:creatinine≥ 2.5g/mol (males), ≥ 3.5g/mol (females)

Table 1. Odds ratios, adjusted for age and sex, for the association between stage of diabetes and renal function

Figure 2. Prevalence of microalbuminuria and chronic kidney disease across the diabetes continuum

1.00Normal glucose0.61(0.60-2.38)1.20IFG

0.02(1.13-4.78)2.33IFG

MICROALBUMINURIA

Diabetes

CHRONIC KIDNEY DISEASEDiabetes

Normal glucose

<0.001(2.06-4.63)3.09

1.00

0.31(0.84-1.76)1.21

p-value(95% CI)OR

Normal glucose

FPG < 6.1mmol/L

Impaired fasting glucose

FPG ≥ 6.1 & < 7.0mmol/L

Diabetes

FPG ≥ 7.0mmol/L or self-reported

Figure 1. Definitions and prevalence across the diabetes continuum at Stage 2 of the North West Adelaide Health Study

90.6%

(n=2880)

2.2%

(n=71)

7.2%

(n=228)

The prevalence of each stage of the diabetes continuum is shown in Figure 1.

Figure 2 shows that the proportion of participants with microalbuminuria was statistically significantly higher (p<0.001) among those with impaired fasting glucose (IFG, 14.8%) or diabetes (20.0%) than those with normal glucose (4.2%). Similarly, the proportion with chronic kidney disease was also statistically significantly higher among those with IFG (22.5%), or diabetes (25.5%) than those with normal glucose (10.1%).

After adjusting for the effects of age and sex, both IFG and diabetes were associated with microalbuminuria, but not chronic kidney disease (Table 1).

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25

30

35

Microalbuminuria Chronic kidney disease

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Normal IFG Diabetes

* Levy et al. MDRD Study Group. Ann Intern Med 1999;130:461-70.