Prevalence of diabetes mellitus in an ambulant elderly New Zealand population

The prevalence of diabetes mellitus (both known and previously undiagnosed) was studied in a population sample, predominately Caucasoid and resident in the community with an age/sex distribution representative of the New Zealand population aged 65 + years, using WHO criteria. The population sample was randomly selected from the age/sex register of a large urban medical centre in Christchurch, New Zealand. Three hundred and sixty-nine subjects (participation rate 69.4%) were screened by casual glucose and glycated haemoglobin measurement, followed by oral glucose tolerance testing (OGTT) if one or both were elevated. The minimum prevalence rate of diabetes in the study sample was 17.2 ± 3.3% in men and 12.5 ± 2.2% in women (since not all patients underwent OGTT). The rate was only significantly higher in men than women in the 70–74 year age group ( P < 0.01). The combined age-adjusted prevalence rates for the New Zealand elderly are estimated to be 9.9% known diabetes, 5.0% previously undiagnosed, with the total prevalence rate 14.9%. Newly diagnosed subjects had a significantly higher body mass index than known diabetic or non-diabetic subjects ( P < 0.01). Eighty-two percent of newly diagnosed subjects had visited their general practitioner at least once during the previous 6 months. Measurement of glycated haemoglobin had a greater positive predictive value than casual blood glucose in the detection of new cases. There was no difference in frequency of attendance with general practitioners or in hospital admission rates between non-diabetic patients, or those with known or newly diagnosed diabetes. This study suggests that diabetes mellitus may be a prevalent disorder amongst the New Zealand elderly.