In Hong Kong, diabetes mellitus is very common in the Chinese population. Its prevalence is 4-5% in adults of working age , rising to 10% in subjects over the age of 60 and 17% in those over 75 . Diabetes mellitus in Hong Kong is predominantly non-insulin-dependent, even in the young . Our studies of drug-related admissions to the Prince of Wales Hospital, which serves one-fifth of the population in Hong Kong, have shown that hypoglycaemia due to sulphonylureas or insulin (25-43%) and upper gastrointestinal haemorrhage (30-37%) are the two most important adverse drug reactions [4, 5]. We have also shown in a case-control study that old age and impaired renal function are two important risk factors for sulphonylurea or insulin-induced hypoglycaemia . Others have reported that knowledge of hypoglycaemic symptoms is poor in elderly patients with diabetes , rendering this group particularly susceptible to hypoglycaemic attacks.
In the present study, the relationships between age and knowledge of diabetes mellitus and hypoglycaemic symptoms and adherence to medical advice were determined in a cohort of patients with non-insulin-dependent diabetes.
Subjects and methods
During a 7-week period between January and March 1995, all patients with non-insulin-dependent diabetes mellitus seen at the general medical clinic of the Hong Kong Buddhist Hospital--a 350-bed general district hospital which also admits patients for convalescence from other hospitals--were considered for inclusion in the study. After the nature and purpose of the study were explained, informed consent was obtained from each patient. Those patients who could not give a history or who were unwilling to wait until they had been interviewed were excluded.
All participants were interviewed by one of three pharmacy students (K.S.Y.C., C.K.C.C., C.W.S.Y.) under the supervision of the two physicians in charge of the clinic (C.Y.Y., S.L.S.T.). Relevant data were obtained from the patients and their medical records, including age, sex, duration and treatment of non-insulin-dependent diabetes mellitus, presence and extent of diabetic complications, attendance at diabetes education classes, previous hypoglycaemic attacks, other medical conditions, blood glucose, [HbA.sub.1c] and renal and liver function tests.
All participants then answered two questionnaires, designed to evaluate their knowledge of diabetes mellitus and adherence to medical advice (Table 1) and knowledge of hypoglycaemic symptoms (Table 2). The former had been used in a previous study of 111 patients attending a specialist diabetic clinic in Hong Kong . The latter had been used in the UK to study the knowledge of 45 diabetic patients aged 61-82 years . `Unsteadiness' was the only symptom omitted from the original UK list due to the difficulties in finding a meaningful, easily understandable equivalent in Chinese. If patients could not read as a result of illiteracy or poor vision, the questions were read to them. Great care was taken to avoid asking leading questions. If a patient gave all `correct' answers and indicated a strict adherence to medical advice, they would be awarded the maximum scores of 10 for the diabetes knowledge questionnaire and 13 for the list of symptoms.
Table 1. Questions designed to test knowledge of diabetes mellitus and compliance with medical advice
Please answer the following questions:
1. What is wrong with the blood glucose level in your blood? 2. What do the tablets or insulin do to your blood glucose? 3. Do you take your meals regularly every day? 4. What would happen if you miss a meal? 5. What would happen if you took too many tablets/injected too much insulin? 6. If you feel dizzy, hungry and sweaty, what is happening? 7. Do you carry your diabetic outpatient clinic card with you all the time? 8. What should you do if you have an attack of hypoglycaemia? 9. Do you carry sugar cubes (or sweets) with you? 10. Do your relatives know you have diabetes?
From Kumana et al. (1988) .
Table 2. Questions designed to test knowledge of hypoglycaemic symptoms
Which of the following are symptoms of hypoglycaemia? (answer yes, no or don't know)
1. Sweating 2. Weakness 3. Palpitations 4. Hunger 5. Anxiety 6. Speech disturbance 7. Tingling lips 8. Confusion 9. Inability to concentrate 10. Visual disturbance 11. Faintness 12. Sleepiness 13. Headaches
Adapted from Thomson et al. (1991) .
The data are expressed as mean values [+ or -] SD. The significance of differences for all variables was tested 2 using the Wilcoxon signed rank, order alternative or [chi square] tests, where appropriate. P values of [is less than] 0.05 were considered statistically significant.
Of the 230 non-insulin-dependent diabetic patients who attended the clinic during the study period, 126 satisfied the entry criteria and agreed to participation. Their clinical characteristics are shown in Table 3. Half of the patients had diabetes for more than 5 years. Only 0.8% of patients were receiving insulin therapy. [HbA.sub.1c] had been requested during the last visit for only 10 patients: one of the three men and four of the seven women in this group had levels above the normal range.
(a) Normal range: men, 57-126 [micro] mol/l; women, 44-107 [micro] mol/l.
(b) Diabetes education class attended in previous 3 months.
The relationships between age and knowledge of diabetes mellitus (tested by questions 1, 2, 4, 5, 6, 81) and compliance with medical advice (tested by questions 3, 7, 9, 10) are shown in Figure 1. There was a clear age-related decline in the number of patients giving the 'correct' answer to all of the questions testing knowledge of diabetes. However, a similar decline was seen for only two of the four questions testing compliance with medical advice (questions 7 and 9). The overall scores in these 10 questions amongst patients aged [is less than or equal to] 55 (n = 26), 56-65 (n = 32), 66-75 (n = 53) and [is greater than or equal to] 76 (n = 15) years were 5.1 [+ or -] 0.4, 4.2 [+ or -] 0.3, 3.5 [+ or -] 0.2 and 2.7 [+ or -] 0.3 (overall 3.9 [+ or -] 0.2).
[Figure 1 ILLUSTRATION OMITTED]
The relationship between age and knowledge of hypoglycaemic symptoms is shown in Figure 2. There was generally an age-related decline in the number of patients giving the correct answer to all questions except one (question 7: "Are tingling lips a symptom of hypoglycaemia?"). The overall scores in these 13 questions among patients aged [is less than or equal to] 55, 56-65, 66-75 and [is greater than or equal to] 76 years were 6.0 [+ or -] 0.7, 4.4 [+ or -] 0.7, 3.8 [+ or -] 0.5 and 1.9 [+ or -] 0.9 (overall 4.2 [+ or -] 0.4). Thirty-nine patients included in this study had already experienced one or more hypoglycaemic attacks. Their knowledge of diabetes mellitus and hypoglycaemic symptoms and compliance with medical advice did not differ from the remaining 87 patients (Table 4).
Table 4. Knowledge of diabetes mellitus and hypoglycaemic symptoms and adherence to medical advice in relation to the occurrence of previous hypoglycaemic attacks in 126 patients with non-insulin-dependent diabetes mellitus
(a) In past 3 months.
(b) See Table 1 and Kumana et al. (1988) .
(c) See Table 2 and Thomson et al. (1991) .
None of the P values were significant.
[Figure 2 ILLUSTRATION OMITTED]
Twenty-three of our patients had never attended an education class before. Their knowledge of diabetes mellitus and hypoglycaemic symptoms and compliance with medical advice were worse than those who had done so (P [is less than] 0.001; Table 5). Among the latter group, knowledge and compliance with medical advice declined with time (P [is less than] 0.001).
Table 5. Knowledge of diabetes mellitus and hypoglycaemic symptoms and adherence to medical advice in relation to previous attendance of diabetes education class in 126 patients with non-insulin-dependent diabetes mellitus
NS, not significant.
(a) See Table 1 and Kumana et al. (1988) .
(b) See Table 2 and Thomson et al. (1991) .
We have clearly shown an age-related decline in knowledge of diabetes mellitus and hypoglycaemic symptoms among patients with non-insulin-dependent diabetes in Hong Kong. The difference between younger and older patients was particularly marked for the questions "What is wrong with the glucose level in your blood?", "What do the tablets or insulin do to your blood glucose?", "If you feel dizzy, hungry and sweaty, what is happening?" and "What should you do if you have an attack of hypoglycaemia?". Very few patients in all age groups knew what would happen if they missed a meal or they took too many tablets or injected too much insulin. In this study, symptoms most commonly thought to be suggestive of hypoglycaemia by the younger patients (in order of frequency) were: sweating, hunger, visual disturbance, faintness, palpitations, anxiety, inability to concentrate, sleepiness and contusion (Figure 2).
Although previous studies have shown deficiencies in the knowledge of elderly diabetic patients 17, 91, they were either small  or failed to show a clear inverse relationship  or any relationship  between patient's age and knowledge. Moreover, they have not assessed patient's knowledge of other aspects of diabetes mellitus and compliance with medical advice. Knowledge of patients in relation to diabetic: education has also not been examined.
The previous study from Hong Kong  had included a younger age group (mean age 56 years; 20 aged [is less than or equal to] 45 and 91 aged [is greater than] 45 years). The test scores to our first questionnaire did not differ between these groups (5.0 [+ or -] 2.1 versus 4.7 [+ or -] 1.9, P = 0.55). The overall test score of 3.9 [+ or -] 0.2 was considerably lower in our patients who were older. These earlier investigators did not study the influence of diabetic education or the detailed knowledge of hypoglycaemic symptoms in their patients. Since their patients were from a specialist diabetic clinic, which may have more manpower and support, their findings may not be applicable to most patients in Hong Kong.
Others have reported that elderly diabetic patients who have experienced hypoglycaemic attacks previously have greater knowledge of the following symptoms: weakness, sweating, confusion, inability to concentrate, palpitations, speech disturbance and tingling lips . These patients have probably learnt from their own experience. However, this was not seen in the present study.
We have shown that the knowledge of diabetes mellitus and hypoglycaemic symptoms and compliance with medical advice was better in elderly patients who had previously attended a diabetes education class. We have also shown that even among patients who have attended a diabetes education class, knowledge and adherence to medical advice can deteriorate with time. Although all diabetic patients are encouraged to attend formal education classes every 2 months, less than one-third of patients in this study had actually done so in the past 3 months. There should be extra effort to reemphasize the importance of continuing education programmes.
As can be seen in Table 3, 89% of our patients were living with their relatives. In the event of a hypoglycaemic attack, their relatives could help by initiating treatment and/or seeking hospital treatment immediately, These actions would be undertaken only if patients could convey the significance of their symptoms and their relatives could recognize the occurrence of hypoglycaemia in patients. Hence, future studies of knowledge of hypoglycaemic attacks should also target patients' relatives.
Apart from the lack of knowledge of hypoglycaemic symptoms, there are other reasons why elderly diabetic patients on insulin or sulphonylureas may be more susceptible to severe hypoglycaemia . An age-related decrease in the oxidative clearance of drugs has been demonstrated; oxidative metabolism of sulphonylureas in the liver may therefore be impaired in elderly patients . Renal function may deteriorate with ageing, in addition to the development of diabetic nephropathy. In this study, 23% of patients had plasma creatinine concentrations above the normal range (Table 3). Spontaneous hypoglycaemia can occur in non-diabetics with uraemia, due to altered clearance of insulin and glucose metabolism . In diabetic patients with uraemia, hypoglycaemia can also be precipitated by alternation of sulphonylurea metabolism and excretion . Chlorpropamide, the sulphonylurea with the longest half-life, is partly excreted by the kidney as the unchanged parent drug and can accumulate in uraemia. An active metabolite of glibenclamide can accumulate in the presence of renal impairment and cause prolonged hypoglycaemia . As a result of the age-related decline in [Beta]-adrenoceptor function  and hence the warning symptoms of tachycardia and tremor, elderly diabetic patients may be unaware of a hypoglycaemic attack. There is an age-associated impairment of glucose counter-regulation attributed to decreased insulin clearance, reduced glucagon secretion and possibly the delayed adrenaline secretion . Drug interactions are also more likely to occur at this age group .
Diabetes mellitus is a common condition in elderly people in Hong Kong. Because sulphonylurea or insulin-induced hypoglycaemia is potentially fatal and old age is an important risk factor, education of this patient group needs to be improved. Particular caution is needed when prescribing sulphonylureas or insulin for elderly patients, and over-zealous treatment should be avoided. Future studies should identify factors associated with non-attendance at education classes.
* In patients with non-insulin-dependent diabetes mellitus, knowledge of diabetes mellitus and hypoglycaemic symptoms and adherence to medical advice declined with age and time since last diabetic education class.
* Elderly diabetic patients should receive a continuing programme of education about the disease and its treatment.
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Received 14 March 1997
CHO YIN YUNG, SAMUEL L.S. TSE, KENNETH S.Y. CHAN(1), CHRIS K.C. CHOW(1), CECILIA W.S. YAU(1), THOMAS Y.K. CHAN(1), JULIAN A.J.H. CRITCHLEY(1)
Department of Medicine, Hong Kong Buddhist Hospital, Kowloon, Hong Kong
(1) Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong
Address correspondence to: T.Y.K. Chan. Fax: (+852) 26 32 3108
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