QJM Advance Access originally published online on July 2, 2009
QJM 2009 102(9):603-607; doi:10.1093/qjmed/hcp082
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Nocturnal hypoglycaemia in type 1 diabetes—frequency and predictive factors
From the 1Department of Diabetes and Endocrinology, University of Liverpool, Clinical Sciences Centre, Aintree University Hospital, L9 1AE and 2Department of Diabetes and Endocrinology, Royal Liverpool University Hospital, Prescot Street, Liverpool L7 8XP, UK
Address correspondence to A. Woodward, Department of Diabetes and Endocrinology, University of Liverpool, Clinical Sciences Centre, Aintree University Hospital, L9 7AL, UK. email: a.woodward{at}liverpool.ac.uk; annwoodward4{at}btinternet.com
Received 2 December 2008 and in revised form 27 May 2009
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Abstract |
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Background: Nocturnal hypoglycaemia (NH) remains a problem in type 1 diabetes and spontaneous asymptomatic NH may be a risk factor for sudden death (‘Dead in Bed’ syndrome).
Aims: To explore whether any predictive relationship exists between the average or time-specific glycaemia and the occurrence of NH.
Methods: Twenty-five healthy patients with type 1 diabetes underwent two separate overnight periods of continuous glucose monitoring (CGM) using a MMT-7002 Medtronic MiniMed System. There was a 6-week interval before the second monitoring period. CGM glucose levels recorded between 23:00 and 08:00 h defined the nocturnal period and recorded glucose monitoring levels <3.5 mmol/l for at least 10 min during this time-defined NH. A CGM recording at 23:00 h and 08:00 h were taken as the bedtime and fasting glucose levels, respectively.
Results: The mean ± SD age was 37 ± 7 years and duration of diabetes 13 ± 7 years; 16 (64%) were on long-acting analogue insulin. Forty-nine CGM data sets were recorded. Fourteen episodes of NH occurred in 12 patients (Group 1), 13 patients (Group 2) had no NH. Group 1 (NH) had a lower mean bedtime glucose recorded compared with Group 2 (7.7 ± 4.3 vs. 11.4 ± 4.0 mmol/l, P = 0.0035). Fasting glucose level was also lower in Group 1 following the occurrence of NH (P = 0.014). There was no difference in the type of insulin used between the two groups.
Conclusions: Our data show that in normal day to day settings, NH is common and that the bedtime glucose level is a significant predictive factor.