Dementia detection from brain activity during sleep

STUDY OBJECTIVES

Dementia is a growing cause of disability and loss of independence in the elderly, yet remains largely underdiagnosed. Early detection and classification of dementia can help close this diagnostic gap and improve management of disease progression. Altered oscillations in brain activity during sleep are an early feature of neurodegenerative diseases and be used to identify those on the verge of cognitive decline.

METHODS

Our observational cross-sectional study used a clinical dataset of 10 784 polysomnography from 8044 participants. Sleep macro- and micro-structural features were extracted from the electroencephalogram (EEG). Microstructural features were engineered from spectral band powers, EEG coherence, spindle, and slow oscillations. Participants were classified as dementia (DEM), mild cognitive impairment (MCI), or cognitively normal (CN) based on clinical diagnosis, Montreal Cognitive Assessment, Mini-Mental State Exam scores, clinical dementia rating, and prescribed medications. We trained logistic regression, support vector machine, and random forest models to classify patients into DEM, MCI, and CN groups.

RESULTS

For discriminating DEM versus CN, the best model achieved an area under receiver operating characteristic curve (AUROC) of 0.78 and area under precision-recall curve (AUPRC) of 0.22. For discriminating MCI versus CN, the best model achieved an AUROC of 0.73 and AUPRC of 0.18. For discriminating DEM or MCI versus CN, the best model achieved an AUROC of 0.76 and AUPRC of 0.32.

CONCLUSIONS

Our dementia classification algorithms show promise for incorporating dementia screening techniques using routine sleep EEG. The findings strengthen the concept of sleep as a window into neurodegenerative diseases.

Restriction fragment length polymorphism of Mycobacterium tuberculosis strains from various regions of India, using direct repeat probe

Intraspecies differentiation was studied on 68 M. tuberculosis strains obtained from 6 states of India by restriction fragment length polymorphism (RFLP) using a direct repeat probe (DR probe) hybridised with Alu I digest of DNA. Most strains showed polymorphism based patterns that comprised between 2 to 7 bands and were grouped into 26 RFLP types. Of the 11 strains tested from Amritsar, 8 were RFLP type 5; the remaining 3 were of type 11 and were exclusively confined to this region. The strains from other regions were more heterogeneous. We confirm that DR-associated RFLP can be an excellent tool for the differentiation of M. tuberculosis strains. Depending on their geographical origin, these strains can be differentiated to a large extent by DR fingerprinting.

Does BCG vaccine prevent tuberculous meningitis?

The reported efficacy of BCG vaccine in preventing pulmonary tuberculosis varies from 0-80%; however, its efficacy in preventing tuberculous meningitis ranges from 52%-84%. A case-control study was conducted to assess the efficacy of BCG in preventing tuberculous meningitis in children. New cases of tuberculous meningitis, confirmed bacteriologically, were registered as cases. Controls were children suffering from febrile convulsions attending the same hospital. A total of 107 cases and 321 controls, block matched for age, were registered. Vaccination status was determined from the history reported by the mother and by BCG scar reading. Data regarding socioeconomic status, crowding, and nutritional status were collected. Using multiple logistic regression analysis the odds ratio obtained for the presence of BCG scar was 0.23 (95% confidence interval (CI) 0.14 to 0.37) and the protective efficacy of BCG vaccine in preventing tuberculous meningitis in children was found to be 77% (95% CI 71 to 83%).

Tuberculous meningitis in children--clinical profile, mortality and morbidity of bacteriologically confirmed cases

One hundred and seven cases of tuberculous meningitis were registered as a part of a case-control study during the period 1990-1992. The CSF of all cases was positive for culture and/or smear for acid fast bacilli. Children were examined at the time of admission and at the time of discharge and they were contacted at the end of 1 year. Clinical picture, mortality and morbidity were analyzed. Mortality of children during the first month of illness was 22%. Some of the cases presented as acute neurological illness. We also came across CSF picture with minimal cytological and biochemical changes but with positive culture results.

Testing compliance of drug taking--a simple bed side method

Assessment of compliance in drug taking is a problem in a crowded Outpatient Department. Using riboflavin as a urinary marker is a simple and rational method. Identifying riboflavin in the urine by fluorescence on exposure to ultraviolet (UV) rays or torch light is being used in medical practice but not extensively. In this study, the validity and reliability of these methods were assessed. The sensitivity and specificity of this test by UV method was 86% and 82% for Reader I (medical person) and 82% and 94% for Reader II (paramedical person). For Reader I, the accuracy of reading by UV lamp was the same as torch light (85%) whereas for Reader II the accuracy was better with UV lamp (87%) than with torch (79%). In reading the fluorescence by UV lamp the crude agreement between the 2 readers was 82% and chance corrected agreement was 64%. UV lamp method appears to be a reliable way of assessing compliance both by medical and paramedical persons whereas torch method appears to be more reliable when used by a medical person than by a paramedical person.

Early bactericidal action of pulsed exposure to rifampicin, ethambutol, isoniazid & pyrazinamide in pulmonary tuberculosis patients

The bactericidal action of two therapeutic regimens on Mycobacterium tuberculosis was assessed by viable counts in serial sputum samples in 49 pulmonary tuberculosis patients being treated with rifampicin (R), ethambutol (Emb), isoniazid (I) and pyrazinamide (Z) together in a single dose thrice weekly (REmbIZ3) or with REmb and IZ on alternate days (REmb3IZ3alt). In both groups of patients, there was a significant reduction (P < or = 0.02) in the colony forming units (cfu) of M. tuberculosis per ml of sputum during the first two days of treatment itself. This early bactericidal action (EBA) as well as the reduction in counts during the subsequent days of treatment were similar (P > 0.2) for both REmbIZ3 and REmb3IZ3alt regimens indicating that splitting up REmbIZ into REmb on one day and IZ on the next day in short course chemotherapy (SCC) regimens may not affect the bactericidal action of the regimens.

Evaluation of a cold staining method for acid-fast bacilli in sputum

Comparison between the Ziehl-Neelsen staining method for acid-fast bacilli, applied with and without heating, was carried out in a controlled investigation using smears prepared from 306 sputum samples collected prior to treatment from suspected cases of pulmonary tuberculosis. Smear and culture positivity were graded and the colour intensity of bacilli recorded. Results showed that the chance corrected agreement (Kappa) between Z-N and cold methods was only 78%. The sensitivity of the Z-N and cold methods were 84% and 77% respectively when compared with culture results. Assuming 10% smear positivity among symptomatics reporting to Peripheral Health Institutions (PHIs), the positive predictive value of the cold method was very low (53%). When compared to culture, the positive predictive value is 71% for the Z-N method and 57% for the cold method for a symptomatic population with 15% culture positivity. In the absence of heating, penetration of the stain was significantly reduced and consequently the number of bacilli detected was less. The inability to take the stain without heating was seen in smears from all grades of culture positive samples; thus even heavy positives were missed by the cold method. The evaluation of the cold method against the standard Z-N method highlights its limitations and demonstrates that it is not as reliable as the standard Z-N method.

Heriditary pattern of cancer

Three thousand nine hundred and twelve patients with cancer in various sites reporting to the out patient department were questioned for history of cancer among blood relatives. A positive history of cancer was obtained in 154 of whom 89 were male and 65 female. Thirty nine patients gave history of cancer among siblings and five gave history of cancer among spouses related by consanguneous marriage. The other 110 gave history of cancer among second and third generation relatives. Sixty one percent maternal relatives of the female patients had cancer as compared to only 33 percent of paternal relatives. This difference was not seen among male patients where there were about 45 percent of maternal and 47 paternal relatives giving history of cancer. Further it was found that 6 of 20 patients with cancer of the breast, 7 of 22 with stomach cancer and 4 of 12 with cervix cancer had blood relatives with the same type of cancer.

Association between obesity and hypertension in south Indian patients

Two hundred and forty four newly diagnosed hypertensives (cases) of age 40 years and above, attending the hypertensive clinic of the Government General Hospital during one year and three hundred and twelve normotensives (controls) belonging to the same age group and attending the outpatient department during the same period for other minor ailments formed the subjects for this case control study. There were 18 (7.4%) obese subjects among hypertensives and 6 (1.9%) among controls. In spite of these low proportions, there was a strong association between obesity and hypertension with an overall odds ratio of 4 and there appeared to be a significant increasing trend in the proportion of cases of hypertension (37%, 63%, 75%) observed according to the different grades (underweight or normal, overweight, obese) of nutrition.

Role of phenobarbitone in preventing recurrence of febrile convulsions

A randomized double blind placebo controlled trial was carried out to study the effect of phenobarbitone (PB) in preventing recurrences of simple and atypical febrile convulsions among children in the age group 6 months to 6 years. Children with simple febrile convulsions were randomly allocated to receive either phenobarbitone or placebo. Children with atypical convulsions were treated with phenobarbitone, as a third group. Thirty children were admitted in each group. All the children were followed up for a period of twelve months. Recurrence of convulsions and side effects of PB were recorded. Recurrence occurred in only 7% (95% confidence interval: 1-22) of children on Phenobarbitone, suffering from either simple or atypical febrile convulsions, compared to 53% (95% confidence interval: 34-72) of children on placebo, suffering from simple febrile convulsions. With Phenobarbitone, 5% of children had intolerable side effects. These results suggest that long term prophylaxis with phenobarbitone, even in simple febrile convulsions will be useful.

Salivary cortisol in the assessment of adrenocortical function in patients with pulmonary tuberculosis

Adrenocortical function was assessed on the basis of changes in salivary cortisol in patients with pulmonary tuberculosis and the findings compared with those in healthy subjects. A method of direct radioimmunoassay of salivary cortisol was standardized and the sensitivity was 0.8 nmol/l. Cortisol levels in saliva were significantly higher in the patients than in the healthy subjects (P less than 0.001). The diurnal rhythm of cortisol secretion was disturbed in the patients with a significant increase in salivary cortisol beyond 1800 h. While dexamethasone caused an appreciable suppression (87%), stimulation with ACTH (tetracosactrin) resulted in a marked increase in salivary cortisol, the increase being significantly higher in the healthy subjects than in the patients (P less than 0.001). Attempts to classify subjects as positive or negative responders to tetracosactrin based on increases in salivary cortisol in relation to plasma cortisol changes were however not successful, as the agreement between the two methods ranged from 73 to 80 per cent with various criteria used.

Adrenocortical function in patients with pulmonary tuberculosis

Adrenocortical function was studied in patients with pulmonary tuberculosis and the findings compared with those in healthy subjects. Plasma cortisol levels in newly diagnosed patients were appreciably higher than in the healthy subjects (P less than 0.001). A normal (positive) response to ACTH (tetracosactrin) stimulation was observed in 35 (97%) of 36 healthy subjects, 15 (56%) of 27 newly diagnosed patients with tuberculosis and 5 (42%) of 12 chronic cases (i.e. those who had had the disease for more than 3 years); the difference between the healthy subjects and the two groups of tuberculosis patients was highly significant (P less than 0.001). Dexamethasone caused an appreciable decrease in the plasma cortisol levels of tuberculosis patients. Considering the diurnal variation of cortisol secretion, there was a steady decline in the cortisol levels between 08:00 and 20:00 in the healthy subjects (P = 0.02); in the tuberculosis patients, however, there was a decrease up to 16:00 followed by a significant increase (P = 0.05), and the mean value at 20:00 was similar to that at 08:00.

Age for measles immunization seroconversion after measles vaccination at 6-8 months of age--a randomized controlled trial

The objective of the study was to compare the effectiveness of measles vaccine by seroconversion in vaccinated children with non-vaccinated children of 6 to 8 months age group in a city slum community so as to study the feasibility of advancing the age of immunization. Live attenuated lyophilized Schwartz strain of measles vaccine was used. Hemagglutination inhibition (HI) antibody was estimated. Seroconversion was defined as either the conversion of negative to positive or a two fold rise in titre. One hundred and thirty two children completed the study. There was no difference in the age, sex and nutritional status between vaccinated and non-vaccinated groups (p greater than 0.7). The seroconversion rate in the vaccinated group was 65% and in the non-vaccinated group was 26%. The age, sex and nutritional status did not significantly affect the seroconversion. Our data suggest that immunization with measles vaccine may be effective as early as 6 months of age. Immunization at 6 months may be needed at least for children in densely populated areas like cities and towns.

Prevalence of placentally transmitted antibodies for measles in infants 3 to 11 months old in an urban slum community

Upto 35% of infants aged between 6 and 11 months are infected with measles in India with its associated high morbidity and mortality. The objective of the study is to know the waning pattern of placentally transmitted antibodies (PTA) for measles so that the age at which children are likely to become susceptible to measles infection could be identified. A cross-sectional serological survey of children aged 3 to 11 months in one of the Integrated Child Development Service (ICDS) area in Madras city slums was done. Venous blood from 376 children was collected and was tested for Hemagglutination Inhibition (HI) antibodies by standard microtitration technique. Titre greater than or equal to 1:8 has been considered as protective. The proportion of children with immune level and the Geometric Mean Titre (GMT), declined to the least by 5 months which denotes that most of the infants become susceptible to measles infection from as early as 5 months of age. There is no significant difference in the waning pattern between different age groups, sex and nutritional status. A community study for effectiveness of measles vaccine at 6-8 months of age is needed to know the feasibility of immunization earlier than 9 months of age.

Pyrazinamide deamidase activity in tuberculous disease

To investigate whether pyrazinamide deamidase activity is suppressed in tuberculosis, serial serum concentrations of pyrazinamide, following 40 mg of pyrazinamide per kg, were determined in 10 patients with sputum positive pulmonary tuberculosis and in 10 control subjects without disease. The concentrations and the half-lives of pyrazinamide were similar in the 2 groups, suggesting no suppression of the deamidase activity in tuberculous patients.