|Year : 2012 | Volume
| Issue : 1 | Page : 44-48
Diabetes mellitus: A risk factor for cognitive impairment amongst urban older adults
SC Tiwari1, Rakesh Kumar Tripathi1, Siddiq Ahmad Farooqi1, Rajesh Kumar2, Garima Srivastava3, Aditya Kumar1
1 Department of Geriatric, BPK Institute of Health Sciences, Dharan, Nepal
2 BPK Institute of Health Sciences, Dharan, Nepal
3 Departmentof Psychology, Allahabad University, Uttar Pradesh, India
|Date of Web Publication||22-Apr-2013|
Rakesh Kumar Tripathi
Department of Geriatric Mental Health, King George's Medical University, Lucknow, Uttar Pradesh, India
Source of Support: Paper is based on an Indian Council of Medical Research (ICMR), New Delhi, India funded research project entitled, gAn epidemiological study of prevalence of neuro.psychiatric disorders with special reference to cognitive disorders mongst urban elderly., Conflict of Interest: None
| Abstract|| |
Background: Studies reported in relation to diabetes mellitus and cognitive impairment are inconclusive. Diabetes mellitus is a wide spread physical illness amongst older adults. The study explores whether, it leads to cognitive impairment amongst older adults in comparison to those without diabetes mellitus. Materials and Methods: Study sample consisted of 900 subjects fulfilling the inclusion/exclusion criteria out of 1067 elderlies aged 55 years and above residing in a randomly selected ward of urban Lucknow. Pathological investigation was done on all elderlies to rule out diabetes mellitus. Out of 900 subjects 145 were found to have Diabetes Mellitus and rests 755 were without diabetes mellitus. These subjects were further divided into two groups: (i) with and (ii) without cognitive impairment based on detailed assessment of Mini Mental State Examination positive subjects by Cambridge Examination for Mental Disorders of the Elderly- Revised (CAMDEX-R). International Classification of Diseases-10 th revision criteria were used to make diagnosis. Data analysis was done calculating odds ratio, Chi square, and percentages. Results: Diabetes mellitus was found to be prevalent is 13.7% and 16.9% amongst older adults aged 55-59 years and 60 years and above respectively. Odds ratio 1.3 with CI 95% indicates that subjects with diabetes mellitus is 1.3 times at more risk to develop cognitive impairment amongst urban older adults than non-cognitively impaired subjects. But differences on Chi square test were found to be insignificant. Conclusion: There is a weak association between diabetes mellitus and cognitive impairment amongst urban older adults.
Keywords: Cambridge examination for mental disorders of the elderly-revised, cognitive impairment, diabetes mellitus, mini mental state examination, prevalence
|How to cite this article:|
Tiwari S C, Tripathi RK, Farooqi SA, Kumar R, Srivastava G, Kumar A. Diabetes mellitus: A risk factor for cognitive impairment amongst urban older adults. Ind Psychiatry J 2012;21:44-8
Diabetes mellitus is a common medical condition known to have adverse effects on all system of human body. Normally, insulin and glucagons are produced by the Islets of Langerhans More Details in the pancreas. Insulin regulates the conversion of glucose to glycogen for storage in various cells. Elevated blood glucose levels can result in brain malfunction and it promotes the synthesis of sorbitol, which damages blood vessels and causes degeneration of the nerves, resulting in neuropathology which can lead to dementia or cognitive impairment. 
With increase in the world population and average life span of the individuals; the prevalence of diabetes mellitus is steadily increasing with other physical and mental health problems. Diabetes mellitus and its complications are important health care problems in the older adults. For mental health problems, it was hypothesized that diabetes mellitus leads to cognitive impairment. Studies available in literature are both in favor, , as well as against ,, this hypothesis. ,,,,,
A national survey of diabetes conducted in six major cities in India in the year 2000 has shown that the prevalence of diabetes in urban Indian adults is 12.1%.  The prevalence of diabetes increases with age and it peaks at 60-69 years of age. With the demographic transition and population aging, diabetes mellitus will be a major public health problem in India. The increased frequency of depression, anxiety and forgetfulness has also been reported in older patients with diabetes mellitus. 
In India alone, diabetic patients are expected to increase from 40.6 million in 2006 to 79.4 million by 2030. Studies have shown that the prevalence of diabetes in urban Indian adults is about 12.1%, the onset of which is about a decade earlier than their western counterparts and the prevalence is higher in urban than in rural areas.  The prevalence rates of diabetes varied from 103 per thousand to 124 per thousand in different studies. In a meta analysis, 118 per thousand prevalence was reported of studies between year 1996 and 2002 for urban adult population. 
From the state of Uttar Pradesh, the current overall prevalence of cognitive disorders is reported 7.6%  in urban older adults aged 60 years and above using stringent methodology. A prevalence of 3.9% was found in rural areas  and in Jaipur  amongst elderlies. In year 2005 Shaji and associates  found prevalence of dementia to be 3.36% in urban population of Kerela aged 65 years and above. In a study by Das and associates  an overall prevalence of 14.89% of mild cognitive impairment (MCI) was found amongst persons aged 50 years and above in Kolkata. Studies, , also reported that diabetes mellitus is the major risk factor for the MCI.
Furthermore, vascular risk factors e.g., hypertension and diabetes also contribute to vascular dementia and mixed Alzheimer's plus cerebro-vascular disease. 
Studies reported in relation to cognitive impairment and diabetes mellitus is inconclusive because of inconsistent reports. The inconsistency in findings may be due to differences in study design, sources of study subjects, and variations in criteria for the diagnosis of diabetes mellitus or cognitive impairment. However, it may also be due to differences in the duration or severity of diabetes mellitus among study subjects. For this study, much precautions were taken care of in inclusion of the subjects from the community, using definite case criteria for diabetes mellitus (fasting and post prandial investigations) and cognitive impairment, assessment by trained clinical psychologists and physicians for diagnostic formulation. Randomly selected 10% of the sample was reassessed to control false positive and negative diagnoses of the subjects. An Indian Council of Medical Research, New Delhi sponsored study, "An epidemiological study of prevalence of neuro-psychiatric disorders with special reference to cognitive disorders amongst urban elderlies"  provided an unique opportunity to explore the prevalence of diabetes mellitus and its impact on cognitive functioning of urban older adults. It was hypothesized that diabetes mellitus is a risk factor of cognitive impairment.
To study the prevalence of diabetes mellitus amongst urban older adults and to study the relationship between diabetes mellitus and cognitive impairment.
| Materials and Methods|| |
Study sample consisted of 900 subjects fulfilling the inclusion/exclusion criteria, recruited out of 1067 elderlies aged 55 years and above residing permanently in a randomly selected ward of urban Lucknow. Out of total 1067 subjects 167 (15.65%) subjects refused to participate in the study because their family members refused to give blood of the subjects for pathological investigations such as blood sugar (fasting and PP), hemoglobin %, Total Leucocyte Count (TLC), Differential Leucocyte Count (DLC), Liver Function Test (LFT), serum urea/createnin and lipid profile.
Mean age of the study sample was found to be 67.17 years. Pathological investigation was done on all 900 study subjects to see the status of diabetes mellitus. Out of 900 subjects 145 were found to have diabetes mellitus and rest 755 subjects were without diabetes mellitus. These subjects were further divided into two groups: (i) with and (ii) without cognitive impairment based on detailed assessment of Mini Mental State Examination (MMSE)  positive subjects by Cambridge Examination for Mental Disorders of the Elderly-Revised (CAMDEX-R).  Age and education specific cut off criteria  was used to determine the MMSE positive and negative subjects to control education bias. International Classification of Diseases-10 th revision (ICD-10)  criteria were used to make diagnosis of cognitive (organic) disorders. Subjects with a definite diagnosis of dementia or subjects having objective cognitive impairment but no dementia (other than dementia) as per ICD-10 criteria (F00-F09 only) were called as cognitively impaired group.
Data was analyzed using statistical test of odds ratio Chi square and percentages.
| Results|| |
The [Table 1] shows the breakup of elderlies with and without diabetes mellitus by age and status of cognitive functioning.
[Table 1] shows that 13.7% pre-elderly (55-59 years) and 16.9% elderly (60 years and above) were found to be suffering from diabetes mellitus amongst urban older adults. The prevalence of cognitive impairment amongst the non-diabetic urban pre-elderlies aged 55-59 years was found to be 1.5%. In pre-elderly group, none of the subjects with diabetes mellitus were found to be having cognitive impairment. The prevalence of cognitive impairment amongst the diabetic urban elderlies aged 60 years and above was found to be 9.6%. However, the prevalence of cognitive impairment amongst the urban elderlies aged 60 years and above without diabetes mellitus was found to be 7.5% which is slightly lower against the prevalence rate of cognitive impairment amongst urban elderlies with diabetes mellitus (9.6%).
Odds ratio was calculated between the two groups i.e., urban elderlies aged 55-59 years and 60 years and above with and without diabetes mellitus with regard to evidence of cognitive impairment in them and it was found to be statistically significant [Table 2]. More than 1 with 95% confidence interval (CI) for both the age ranges indicate that subjects with diabetes mellitus is 1.3 times at more risk to develop cognitive impairment amongst urban older adults than non-cognitively impaired subjects.
|Table 2: Status of cognitive impairment and diabetes mellitus amongst older adults aged 55-59 years and 60 years and above|
Click here to view
However, on Chi square test the differences between cognitively impaired and non-cognitively impaired group on diabetes mellitus among pre-elderly and elderly age group was not found.
| Discussion|| |
In the study the prevalence of diabetes mellitus was 16.9% amongst older adults aged 60 years and above. This is quite high in comparison to other studies which have recorded a prevalence of 12.1%  and 9%,  10.3-12.4%  in Indian adults. However, the present prevalence of diabetes may turn out to be similar to this study as in recent years the prevalence of diabetes in on rapid rise in the Country. But in the light of escalating population, increase of prevalence rate of diabetes is justified. It may be more than reported in this study because in the study sample only those elderlies were included who were found diabetic on blood sugar estimation without consideration to whether they were currently on anti-diabetic medication or not. Many known diabetic elderlies whose blood sugar level may have been within normal range due to intake of anti-diabetic drugs may have been missed inclusion in the study sample.
Highest prevalence of cognitive impairment in the age group 70-79 (138 out of 186) suggests that 8 th decade in life is probably the most susceptible period for becoming the victim of cognitive impairment, and probably those in this age suffering from diabetes mellitus are maximally prone [Table 1].
The statistical analysis of odds ratio in the study has revealed that diabetes mellitus is risk factor for cognitive impairment in urban older adults irrespective of the cut off age of either 55 years or 60 years [Table 2]. Although, the odds ratio was found to be significant on 95% CI but Chi square is not. The range on odds ratio is also more wide (0.6532-2.5684) to predict diabetes mellitus is a risk factor for cognitive impairment. Hence, the finding of the study is not in strong support of the alternative hypothesis that diabetes mellitus is a risk factor of cognitive impairment. It might be due to a small sample size of cognitive impairment based on and cross sectional epidemiological study. Separate study with large sample size of cognitive impairment would be more appropriate to establish the relation of cognitive impairment with diabetes mellitus.
This is an important finding from a preliminary report of a large epidemiological study employing stringent research criteria. The final report of the study will generate large sample size to recheck the findings of the study.
Diabetes mellitus was found to be prevalent is 13.7% and 16.9% in urban older adults amongst older adults aged 55-59 years and 60 years and above respectively. Diabetes mellitus has been found to be a risk factor for cognitive impairment but, with weak significance level amongst urban older adults.
Interventions aimed at diabetes that begins before age 60 might lessen the burden of cognitive impairment in later life.
It is a community based epidemiological study on large sample size using stringent research methodology. Detailed psychological assessments of the subjects by trained clinical psychologists, reliability exercises amongst research team for data collection, and pathological investigations on all the study subjects are the major strengths of the study.
An issue that emerges for more detailed investigations is whether the elderlies whose diabetes is under control with drugs are more skip to non-diabetes or to diabetes in respect of their vulnerability for cognitive impairment. It was also noticed that the sample of cognitive impairment subjects is small to predict strong association. Urban population of north India is different for their dietary habits from the other parts of the country hence; the findings cannot be generalized.
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[Table 1], [Table 2]