DIABETES should be regarded as a multi-organ disease in light of new studies showing that the disease affects lung and hepatic function in ways not previously recognised.

In the first study, diabetes has been linked to impaired lung function of a similar magnitude to that induced by smoking, while a second study has found patients newly diagnosed with diabetes face a much higher risk of serious hepatic disease than the general population.

Restrictive effect on lung function
A systematic review of 40 observational studies involving 3000 patients with type 1 and type 2 diabetes matched to 27 000 controls was undertaken. It found those with diabetes had modestly restrictive impairment to pulmonary function, with a statistically significant difference in FVC, FEV1 and carbon monoxide lung diffusion.

The impairment was observed in patients free of pulmonary disease and irrespective of BMI, smoking history, disease duration or HbA1c level.

The authors, from the Department of Respiratory Medicine at Maastricht University in the Netherlands, said while it would be premature to link cause and effect based on observational data, it was tempting to speculate that uncontrolled disease could accelerate declining lung function.

“[For] those patients with diabetes who carry a pulmonary diagnosis, such as COPD or asthma, it would next be interesting to investigate potential clinical implications,” they wrote in the journal Chest.

Stiffening of the thorax and lung parenchyma resulting from non-enzymatic glycation of collagen and elastin in the lung or microvascular damage were possible mechanisms, they said.

Serious liver disease risk following diagnosis
A second study found patients with newly diagnosed diabetes are also at significantly increased risk of developing serious liver disease including liver failure and cirrhosis.

The Canadian cohort study used health records to track 13 years of data for over 400 000 newly diagnosed adult diabetics, who were matched to over two million controls.

They found a serious liver disease incidence rate of 8 per 10 000 person-years for cases of newly diagnosed diabetes, and a rate of 4 per 10 000 person-years among non-diabetic controls.

After accounting for multiple confounders such as age, hypertension, dyslipidaemia, obesity and cardiovascular disease, the hazard ratio for serious liver disease among the diabetic patients was around 1.77.

The adjusted risk for liver cirrhosis was almost 1.5 times higher for patients with diabetes.

“Although diabetic hepatopathy is potentially less common [than other diabetes complications], it may be appropriate for addition to the list of target-organ conditions related to diabetes,” the authors wrote in the Canadian Medical Association Journal.

They suggested liver function testing might be included in annual diabetes screening tests, but the efficacy of primary and secondary interventions would need to be validated before screening could be recommended routinely.

Chest 2010: 138: 393-406.
CMAJ 2010; DOI:10.1503/cmaj.092144

Posted 23 August, 2010

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