Normative concentrations of urine thiocyanate in cassava eating communities in Nigeria.

Exposure to cyanide is a major public health problem where highly cyanogenic cassava foods are consumed. Thiocyanate (SCN), the biomarker of exposure to cyanide is present in several foods, and produced endogenously. Concentrations of urine SCN were measured in endemic and non-endemic areas of ataxic polyneuropathy in Nigeria. Cassava food consumption in the endemic area was twice that of non-endemic areas. Geometrical mean (95% CI) urine SCN was 20 µmol/l (18-24) for no consumption of cassava foods, 56 µmol/l (49-64) for daily consumption, 56 µmol/l (48-65) for twice daily consumption and 85 µmol/l (62-117) for thrice daily consumption. 95th percentile reference limit was 125 µmol/l for no consumption of cassava food, but 360 µmol/l for thrice daily consumption. Urine SCN is a useful biomarker of exposure to cyanide from cassava foods. There is strong ecological association of exposure to cyanide and endemicity of ataxic polyneuropathy.

Incidence and risk factors of early post-traumatic seizures in Nigerians.

OBJECTIVES: To determine the incidence and risk factors of early post-traumatic seizures (PTS) in Nigerian subjects. METHODS: Subjects were recruited consecutively, classified as mild, moderate or severe traumatic brain injury (TBI), and followed for 168 hrs for development of seizures. RESULTS: There were 266 subjects, 213 (80%) males and 53 (20%) females, with mean age 31 years (sd 18, range 1-80, median 30). Causes of TBI were motor traffic accident (MTA) related in 217 (82%), falls in 25 (9%), struck by objects in 15 (5%), firearms in 4 (2%), sports and recreation in 3 (1%), and failed suicide in 2 (1%). Cumulative incidence of early PTS was 119‰ (95% CI 80-156). Risk factors were age ≤12 years, severity of TBI, history of seizures, and TBI at weekend, but gender and GCS were not. Skeletomotor palsy was independently associated with early PTS. CONCLUSIONS: Incidence of early PTS is high in this population, probably due to the relatively high proportion of severe TBI. Risk factors are TBI severity, young age, history of seizures, and TBI at weekends. The best preventive strategy is reduction of MTA, which causes over 80% of TBI. Prophylactic anti-seizure therapy may benefit subjects with severe TBI and skeletomotor deficits.

Lifetime prevalence and incidence of parasomnias in a population of young adult Nigerians.

Lifetime prevalence, incidence, and risk factors for parasomnias were determined. Past experiences of non-REM, REM, and sleep-transition parasomnias were recorded. Diaries of night sleep duration, parasomnias, perception of aliens, levels of physical activity, headaches and intake of all substances, drugs, and tobacco were kept for 14 consecutive days. A total of 276 subjects were studied. Lifetime prevalences (95% CI) were 725 (668-776) for occurrence of any parasomnia, 43 (25-74) for sleepwalking, 112 (80-155) for sleep terror, 475 (416-533) for nightmares, 225 (179-277) for sleep paralysis, 43 (25-74) for sleep starts, 322 (270-380) for sleep talking, and 344 (291-402) for enuresis. Incidences (95% CI) were 210 (166-262) for occurrence of any parasomnia, 14 (6-37) for sleepwalking, 11 (4-31) for sleep terror, 170 (131-219) for confusional arousal, 18 (8-42) for nightmares, 14 (6-37) for sleep paralysis, 33 (17-61) for sleep starts, and 4 (1-20) for sleep enuresis. Multivariate analysis showed associations of increase occurrence of parasomnias and duration of sleep >7 h (p < 0.05) and intake of alcohol (p < 0.001), but heavy workload before sleep was associated with decreased occurrence of parasomnias (p < 0.01). Gender, smoking, caffeinated drinks, hypnotics, and headaches were not associated with parasomnias. Incidence of presence of aliens (95% CI) in the room was 25(0/infinity) (12-51). This study shows that more than 70% of the population have experienced parasomnias at any time in the past. Nightmares, enuresis, sleep paralysis and night terrors are the commonest parasomnias experienced in the past, while confusional arousal, sleep starts, and nightmares are the commonest parasomnias currently experienced. Incidence estimates show that all parasomnias persist into adulthood at reduced rates, but reduction of occurrence was greatest for enuresis. Long duration of night sleep and intake of alcohol predisposed subjects to higher occurrence of parasomnias.

Sleep habits in Nigerian undergraduates.

BACKGROUND: Quantity of night sleep is shorter than 8 h in several developed countries, but similar data is not available for most African countries. The objective of this study was to describe the quantity of night sleep, factors that are associated with non-restorative sleep, and sleep habits in a population of undergraduates in Nigeria. METHODS: Questionnaires were used to collect information about bedtimes, waketimes, intra-night awakenings, non-restorative sleep, and afternoon naps over a period of 14 days. RESULTS: Mean duration of night sleep was 6.2 h (median 6.0, range 4.5-9.3), while mean duration of daytime naps was 70 min (median 75, range 10-315). Duration of night sleep was associated with day of the week and gender, but not with BMI. Non-restorative sleep, which occurred 25% of total sleep times, was associated with night sleep < or =5 h, hypnotic use, alarm to wake, heavy workload, and afternoon naps. Intra-night sleep awakening occurred 58.5% of total sleep times. Afternon naps were taken by 225 (82%) of subjects. CONCLUSION: Duration of night sleep in this African population is not longer than the duration in Western countries. Intra-night awakening and non-restorative sleep; however, occur more frequently, and afternoon nap is usually in excess of 1 h.

High mortality of subjects with endemic ataxic polyneuropathy in Nigeria.

BACKGROUND: Endemic ataxic polyneuropathy, a neurological syndrome that was thought to be benign, has been shown to persist in some communities in south-western Nigeria, where it was first described in the 1950s. OBJECTIVES: This study was conducted to compare mortality of cases and controls, and to determine if mortality is related to exposure to cyanide from cassava foods. MATERIAL AND METHODS: Cases of endemic ataxic polyneuropathy and two groups of controls, one group living in an endemic community and the other group living in a non-endemic community, were followed for 25 months. The outcome was death from medical causes. RESULTS: A total of 5970 subjects, 204 cases and 5766 controls - 4000 controls in the endemic community and 1766 controls in the non-endemic community, were followed. A total of 153 subjects died, 24 cases, 115 controls in the endemic community, and 14 controls in the non-endemic community. Relative risks of death (95% CI), adjusted for age and gender, were 4.5 (2.3-8.9) for cases (P < 0.0001), but 2.6 (1.5-4.6) for controls living in the endemic community (P = 0.001). CONCLUSION: This study shows that endemic ataxic polyneuropathy decreases survival. The finding of lower risk of death in the community with higher exposure to cyanide from cassava foods indicates that mortality of endemic ataxic polyneuropathy is not associated with exposure to cyanide from cassava foods.

Incidence of endemic ataxic polyneuropathy and its relation to exposure to cyanide in a Nigerian community.

BACKGROUND: The occurrence of ataxic polyneuropathy in an endemic area in south west Nigeria has been attributed to exposure to cyanide from cassava foods. However, it has been shown that the prevalence of ataxic polyneuropathy is not high in several communities in the tropics where exposure to cyanide from cassava foods is high. OBJECTIVES: To determine the incidence of ataxic polyneuropathy in an endemic community, and to compare the intake of cassava foods, exposure to cyanide, and levels of thiols in cases and controls. METHODS: A cohort of 3167 healthy subjects aged 10 years and over in Ososa, Nigeria, was followed for two years, screened, and examined neurologically. Ataxic polyneuropathy was diagnosed if sensory polyneuropathy and sensory gait ataxia were both present. Controls were selected randomly within 10 year age groups of subjects who screened negative. Intake of cassava foods, exposure to cyanide, concentrations of thiols (glutathione, cysteine, and gamma glutamylcysteine) in plasma, and visual evoked potentials were measured. RESULTS: Person-years of follow up were 6246 for 1469 male and 1698 female subjects in the cohort. The incidence of ataxic polyneuropathy was 64 per 10,000 person-years (31 for male and 93 for female subjects). Multivariate odd ratios were 0.78 (95% CI 0.23 to 2.61) for intake of the commonest cassava food, and 1.64 (0.56 to 5.09) for concentration of thiocyanate in plasma. The concentration of thiols was less than the reference limits in two controls, but in none of the cases. The latency of P100 was prolonged in 20 cases (69%) compared with 14 controls (42%) (p<0.05). CONCLUSIONS: The incidence of ataxic polyneuropathy is high in Ososa, Nigeria, but the intake of cassava foods, exposure to cyanide, and levels of thiols, are not related to the occurrence. These findings do not suggest that cyanide is the cause of endemic ataxic polyneuropathy.

Exposure to cyanide following a meal of cassava food.

Exposure to cyanide from gari, a popular cassava food in West Africa, is implicated in the causation of ataxic polyneuropathy and amblyopia, but this has been questioned because cyanide was not detected in gari in a study. This study was carried out to determine if gari is a source of exposure to cyanide. Gari (150 g) containing cyanohydrin, from which 128 micromol of cyanide ions could be released, was dissolved in 500 ml of cold water for each of the 12 healthy subjects to drink. Concentrations of cyanide in plasma and erythrocytes were determined at baseline and following the meal at 30 min, 1 h, hourly for 4 h and two hourly for 12 h. The mean concentrations of cyanide in the plasma were 6 micromol/l (95% CI 2-10) at baseline, 12 micromol/l (95% CI 6-17) at peak and 6 micromol/l (95% CI 2-10) on return to baseline. The mean amount of cyanide absorbed into the plasma was 13 micromol (S.D. 12), while the transit time of absorbed cyanide was 7.3 h (S.D. 2.1). This study shows that exposure to cyanide follows consumption of gari, but the amount of cyanide absorbed into the plasma from a single meal is small and unlikely to cause acute intoxication. The long transit time of absorbed cyanide in the plasma suggests that frequent intake of gari could cause cyanide to accumulate in the plasma.

Low prevalence of ataxic polyneuropathy in a community with high exposure to cyanide from cassava foods.

INTRODUCTION: Ataxic polyneuropathy, which occurs in endemic form in an area in southwest Nigeria, is attributed to exposure to cyanide from cassava foods. Exposure to cyanide from cassava is, however, not exclusive to this endemic area. In this study, the occurrence of ataxic polyneuropathy was compared in two communities in Nigeria, one located in the endemic area and the other located outside the endemic area. Both communities have been shown to have high exposure to cyanide from cassava foods. METHOD: The prevalence of ataxic polyneuropathy in Jobele, Nigeria, a community located outside the endemic area, was compared with the prevalence of ataxic polyneuropathy in Ososa, Nigeria, a reference community located in the endemic area. Subjects aged 10 years and above in both communities were screened for ataxic polyneuropathy. Ataxic polyneuropathy was diagnosed if sensory gait ataxia and sensory polyneuropathy were present. The intake of cassava foods, biomarkers of exposure to cyanide, and intake of protein and sulphur were measured. RESULTS: Prevalence of ataxic polyneuropathy were 490 per 10,000 in Ososa, and 17 per 10,000 in Jobele. The age-adjusted prevalence ratio is 4 (95% CI 0-9). The mean intake of all cassava foods in Jobele was 7 meals/person/week (95% CI 6-8), while the mean intake of all cassava foods in Ososa was 10 meals/person/week (95 % CI 9-11). The concentration of thiocyanate in the plasma was above the reference limit in 65% (95% CI 57-73) in Jobele, and 40 % (95% CI 27-52) in Ososa. The intake of protein was significantly lower in Ososa than in Jobele, but the concentrations of glutathione, cysteine and gamma-glutamylcysteine in the plasma were within the same range in Jobele and Ososa. CONCLUSION: This study shows that the occurrence of ataxic polyneuropathy is low in a community where exposure to cyanide is high. This suggests that exposure to cyanide is not a direct cause of ataxic polyneuropathy.

Loss of residual cyanogens in a cassava food during short-term storage.

Residual cyanogens in gari, the most popular cassava food in West Africa, is implicated in the causation of tropical ataxic neuropathy. Gari is eaten by soaking its granules in cold water or by adding boiling water to make a food called eba. This study was conducted to determine whether loss of the residual cyanogens in gari during short-term storage and when gari is made into eba will reduce dietary cyanide load in consumers. Fifteen samples of gari, nine roasted from cassava mash fermented for at least 4 days (type A) and six roasted from cassava mash fermented for only 1 day (type B), were stored for 4 weeks. Free cyanide, linamarin, and cyanohydrin in gari and in eba made from the gari were determined at weekly intervals for 4 weeks. Free cyanide was absent in all samples of gari. Mean cyanohydrin dropped from 8.4 mg HCN Eq/kg dry weight to 4.6 mg HCN Eq/kg dry weight in type A gari, while it dropped from 3.0 mg HCN Eq/kg dry weight to 1.3 mg HCN Eq/kg dry weight in type B gari. Mean linamarin dropped from 6.6 mg HCN Eq/kg dry weight to 2.8 mg HCN Eq/kg dry weight in type A gari, while it dropped from 1.7 mg HCN Eq/kg dry weight to 0.4 mg HCN Eq/kg dry weight in type B gari. Loss of linamarin and cyanohydrin was significant at P < 0.001 for type A gari and at P < 0.002 for type B gari when the weekly levels were compared with initial values. When gari was made into eba, 36% of cyanohydrin and 47% of linamarin were lost from type A gari, while 38% of cyanohydrin and 5% of linamarin were lost from type B gari. Loss of linamarin and cyanohydrin when gari was made into eba was significant for both types of gari at P < 0.001. This study shows that the loss of cyanohydrin and linamarin in gari during short-term storage and when gari is made to eba will reduce dietary cyanide load in consumers.

The significance of autonomic symptoms in Nigerian diabetics.

Diabetes mellitus is the most common endocrine disorder worldwide and disturbance of autonomic function is a frequent complication. Symptoms of autonomic neuropathy are however non-specific and the aetiology is multifactorial in diabetics. This study was carried out to determine the relationship between symptoms of autonomic neuropathy and pathology of the autonomic nervous system in diabetic patients. A hundred diabetics were studied, 50 with, and 50 without symptoms of autonomic neuropathy. Objective test of autonomic function used were the heart rate responses to deep breathing, to standing and to the Valsava manoeuvre; and the blood pressure responses to standing and to sustained handgrip. There was no significant difference between diabetics with symptoms suggestive of autonomic neuropathy, and those without, with regard to findings on autonomic function testing. While the symptoms were unreliable in determining the presence of autonomic neuropathy, they were significantly related to poor glycaemic control and to peripheral neuropathy (P < 0.01). The symptoms of autonomic neuropathy are non-specific in Nigerian diabetics and may reflect poor glycaemic control rather than autonomic neuropathy. Autonomic function tests should be carried out in diabetics suspected of having autonomic neuropathy.