Fluorosis prevalence among schoolchildren in a fluoridated community in Malaysia.

OBJECTIVES: This study aims to assess the magnitude of the problem of fluorosis among 10-11 year old schoolchildren in a fluoridated area in Malaysia. METHODS: An analytical cross-sectional design was adopted. Sampling of subjects was by a 2-stage systematic random sampling technique in Selangor, a fully fluoridated area. 1,343 10-11 year olds were assessed for fluorosis using the Dean's index. RESULTS: The prevalence of fluorosis was 58.7% (788 subjects); 478 (35.6%) subjects exhibited very mild fluorosis, 196 (14.6%) mild, 102 (7.6%) moderate, 12 (0.9%) severe and 555 (41.3%) no fluorosis. Tooth prevalence was 30.1%. Overall, the Community Fluorosis Index (CFI) was 0.96 and ranged from 0.23 to 1.72. Fifteen out of 30 schools had CFI > 1.0 (medium public health significance). CONCLUSIONS: The prevalence of dental fluorosis in Malaysia (mostly very mild to mild) at 58.7% is indicative of slightly above optimal levels of exposure. There were pockets of areas where fluorosis were of medium public health significance (CFI > 1.0). It must be cautioned that, fluorosis if not monitored closely, can become an increasing public health concern.

Does the use of mean or median Z-score of the thyroid volume indices provide a more precise description of the iodine deficiency disorder status of a population?

Endemic iodine deficiency is largely an environmental problem affecting whole populations. Currently, thyroid volume data from a population are analyzed with the sole objective of obtaining an estimate of goitre prevalence using +97th percentile or +2 standard deviations of an appropriate reference as cut-off. This paper proposes an alternative approach to the analysis and presentation of thyroid volume data using Z-scores (standard deviation scores) of the thyroid volume indices such as thyroid volume-for-age or thyroid volume-for-body surface area. The calculation of the summary statistics of the Z-scores, such as mean or median, provides an alternative to the prevalence-based approach for expressing severity of iodine deficiency disorders (IDD). An advantage of the mean or median Z-score is that it describes the thyroid volume profile (and therefore the IDD status) of the entire population directly, unlike goitre prevalence which gives information only about the extremes of distribution. The frequency curve or histogram of the Z-scores provides a complete picture of the whole distribution. Although qualitatively similar conclusions on IDD severity can be drawn from both analytical approaches, only the Z-score system is able to capture adequately the trends or changes in thyroid size over time, and to establish whether a previously iodine-deficient community's thyroid volume profile has returned to 'normal' (as indicated by a distribution that is not significantly different from that of the reference) following intervention. As a continuous variable, Z-scores are particularly useful for the analysis of data from populations where the sample size is relatively small, or where many individuals lie outside the extreme percentiles of the reference population. In view of its advantages in the context of activities based on single and multiple measurements, the Z-score system is to be preferred for the reporting and use of thyroid volume indices. A desirable consequence of this preference is that national goals will be oriented towards an improvement of the overall thyroid volume profile of the population, rather than just a reduction of the number of individuals at the extremes.

Local versus WHO/International Council for Control of Iodine Deficiency Disorders-recommended thyroid volume reference in the assessment of iodine deficiency disorders.

OBJECTIVE: Iodine deficiency endemia is defined by the goitre prevalence and the median urinary iodine concentration in a population. Lack of local thyroid volume reference data may bring many health workers to use the European-based WHO/International Council for Control of Iodine Deficiency Disorders (ICCIDD)-recommended reference for the assessment of goitre prevalence in children in different developing countries. The present study was conducted in non-iodine-deficient areas in Malaysia to obtain local children's normative thyroid volume reference data, and to compare their usefulness with those of the WHO/ICCIDD-recommended reference for the assessment of iodine-deficiency disorders (IDD) in Malaysia. DESIGN AND METHODS: Cross-sectional thyroid ultrasonographic data of 7410 school children (4004 boys, 3406 girls), aged 7-10 years, from non-iodine-deficient areas (urban and rural) in Peninsular Malaysia were collected. Age/sex- and body surface area/sex-specific upper limits (97th percentile) of normal thyroid volume were derived. Thyroid ultrasonographic data of similar-age children from schools located in a mildly iodine-deficient area, a severely iodine-deficient area, and a non-iodine-deficient area were also collected; spot urines were obtained from these children for iodine determination. RESULTS: The goitre prevalences obtained using the local reference were consistent with the median urinary iodine concentrations in indicating the severity of IDD in the areas studied. In contrast, the results obtained using the WHO/ICCIDD-recommended reference showed lack of congruency with the median urinary iodine concentrations, and grossly underestimated the problem. The local sex-specific reference values at different ages and body surface areas are not a constant proportion of the WHO/ICCIDD-recommended reference. A further limitation of the WHO/ICCIDD-recommended reference is the lack of normative values for children with small body surface areas (<0.8m2) commonly found in the developing countries. CONCLUSION: The observations favour the use of a local reference in the screening of children for thyroid enlargement.

Iodization of village water supply in the control of endemic iodine deficiency in rural Sarawak, Malaysia.

A simple water iodizing system, which incorporates the Venturi principle in combination with the controlled release mechanism of a silicone-sodium iodide elastomer, for the iodization of rural piped-water supply in the control of endemic iodine deficiency has been developed and its effectiveness evaluated in three Iban longhouse villages in the iodine-deficient district of Lubok Antu, Sarawak. Urines were collected for iodine assays from women aged 15-40 years before and at 6 and 12 months after the connection of the iodinating device; goiter assessment was performed on the women at the start and end of the 1-year study. Water samples were collected for iodine assays at 2-weekly intervals. In all three villages, significant and sustained increases in median urinary iodine excretions, reaching levels recommended for an iodine-sufficient population, were observed; goitre prevalences were reduced in all the villages (by 22.6% to 35.8%). The iodine levels in the water ranged from 34 micrograms/l to 212 micrograms/L. In the control village, median urinary iodine excretions remained essentially unchanged but a small increase in goiter prevalence was observed. The iodized water was well received by the villagers and no adverse effects of water iodization were observed. The system functioned unattended throughout the one year period. The cost of providing supplemental iodine via the iodizing device is approximately 60 cents (U.S.) per family per year which is affordable by either the Government or the villagers. It is concluded that the iodizing system offers a new cost-effective strategy for the control of endemic iodine deficiency in Sarawak and may have applications in other areas with similar water sources.

Salt: an ineffective vehicle for iodine delivery to young children in rural Sarawak.

The urinary iodine excretions of women (15-40 y) and young children (< or = 6 y) from two longhouse villages in the iodine-deficient district of Lubok Antu, Sarawak, were compared. One longhouse (Mengkak) was provided with freshly produced iodized salt every two months (one kg per family) while the other (Menjiling) was provided with iodized water via fortification of the village piped-water supply. Spot urines were collected for iodine determination at baseline and at 6 and 12 months after the start of the study. Salt and water samples were collected at monthly intervals. Goiter assessment was performed on the women at the start and end of the one-year study. The mean iodine concentrations in the salt samples from Mengkak and Menjiling were, respectively, 47.1 +/- 9.7 mg/kg (n = 60) and 0.8 +/- 3.4 mg/kg (n = 60) while the mean iodine concentration in the water samples from Menjiling was 138.6 +/- 43.2 micrograms/L (n = 24); iodine could not be detected in the water samples from Mengkak. There were significant and sustained increases in median urinary iodine excretions of both women and young children in Menjiling; in Mengkak, however, significant and sustained increases in median urinary iodine excretions were observed only in women while the median urinary iodine excretions of children remained essentially unchanged throughout the study period. Goiter prevalences in the women were reduced in both longhouses. The above observations reveal the inadequacy of iodized salt as a vehicle for iodine delivery to young rural Sarawakian children and indicate the need for other means of delivering supplemental iodine to this age group in areas where salt iodization is the only strategy for IDD control. In contrast, iodization of village water supply by itself is adequate in delivering iodine uniformly to the whole community.

The impact of permethrin impregnated bednets on the malaria vector Anopheles maculatus (Diptera: Culicidae) in aboriginal villages of Pos Betau Pahang, Malaysia.

The effect of permethrin impregnated bednets on Anopheles maculatus Theobald was studied in four villages in Pos Betau, Pahang, Malaysia from August 1990 to July 1992. Collections of mosquitos were carried out indoors and outdoors from 1900 to 0700 hours. All mosquitos were dissected for sporozoites and parity. In May 1991 two villages received bednets impregnated with permethrin at 0.5 g/m2 and two villages received placebo bednets. There was a significant difference in the sporozoite and parous rates between the treated and control villages after the distribution of bednets (p < 0.05). There was no significant difference in the bites/man/night of An. maculatus between the pre and post treatment periods in the control villages. However there was a significant difference in bites/man/night between pre and post treatment in the treated villages (p < 0.001).

Endemic goiter in the Lemanak and Ai river villages of Sarawak.

In a survey of 974 villagers (408 males, 566 females; ages = 11-82 years) of the Ai (n = 496; 212 males, 284 females) and Lemanak (n = 478; 196 males, 282 females) rivers in the district of Lubuk Antu in Sarawak's Sri Aman Division during July 1993, goiter was found in 31.8% of the subjects. The goiter prevalence was higher in the more interior Ai river area than in the Lemanak river area (36.9% vs 26.5%). In females aged 15 years and above, the goiter prevalence was 75.4% and 49.1%, respectively, in the Ai and Lemanak river areas. The difference in goiter prevalence between the two areas was related to the degree of iodine deficiency in the two areas. The median urinary iodine excretion in the Ai river villagers was 22.1 micrograms/l compared to 72.9 micrograms/l in the Lemanak river villagers (p < 0.0001). Goitrous subjects tended to have lower urinary iodine concentration than non-goitrous subjects. In the males, smoking of tobacco was associated with a two-fold increase in goiter frequency. Despite on-going distribution of iodized salt by the medical and health services in the State, only 23% of the 135 salt samples obtained from the households in the areas contained detectable iodine.

Ovalocytosis protects against severe malaria parasitemia in the Malayan aborigines.

The malaria parasite rates and densities were compared in 79 ovalocytic-normocytic pairs of Malayan Aborigines matched for age, sex, proximity of residence to each other, and use of bed nets when sleeping in their jungle settlement in central Peninsular Malaysia. Malaria infection was determined from thick and thin Giemsa-stained blood films collected monthly for a period of six months. Blood films from ovalocytic individuals were found to be positive for malaria less often than in persons with normal red blood cells (P less than 0.05). Malaria infections per 100 person-months at risk were 9.7 in the ovalocytic group compared with 15.19 in the normocytic group. Among individuals parasitemic at any time, heavy infections (greater than or equal to 10,000 parasites/mm3 of blood) with Plasmodium falciparum, P. vivax, and P. malariae were encountered only in normocytic subjects, which comprised approximately 12.5% of the malaria-positive individuals in this group. In an earlier survey of 629 settlers that identified subjects for the above study, the prevalence of ovalocytosis was found to increase significantly with age. The above field observations support the view that ovalocytic individuals might have a survival advantage in the face of malaria. Consideration of the ovalocytic factor is indicated in future evaluations of malaria control measures in areas where ovalocytosis is prevalent.

PIP: The malaria parasite rates and densities were compared in 79 ovalocytic-normocytic pairs of Malayan Aborigines matched for age, sex, proximity of residence to each other, and use of bednets when sleeping in their jungle settlement in central Peninsular Malaysia. Malaria infection was detected from thick and thin Giemsa-stained blood films collected monthly for a 6-month period. Blood films from ovalocytic individuals were found to be positive for malaria less often than in those individuals with normal red blood cells (p0.05). Malaria infections/100 person-months at risk were 9.7 in the ovalocytic group as compared with 15.19 in the other group. Among those parasitemic at any time, heavy infections (or= 10,000 parasites/cu.mm of blood) with Plasmodium falciparum, P. vivax, and P. malariae were seen only in normocytic subjects, approximately 12.5% of the malaria-positive persons in this group. In an earlier survey of 629 settlers who identified subjects for the above study, the prevalence of ovalocytosis was found to increase significantly with age. The above field observations support the view that ovalocytic individuals might have a survival advantage in the face of malaria. Consideration of the ovalocytic factor is indicated in future evaluations of malaria control measures in those areas where ovalocytosis is prevalent.

Platelets of habitual smokers have reduced susceptibility to aggregating agent.

Platelet aggregation to collagen, and productions of 6-keto-prostaglandin-F1-alpha and thromboxane B2 during aggregation were measured after an overnight fast, involving both food and cigarettes, in 19 clinically healthy habitual smokers (10 or more cigarettes/day) and 23 non-smokers receiving the same diet. The subjects (all males; ages = 21-30 years) were residents of a school hostel. Mean platelet aggregation was significantly lower in smokers than non-smokers (23.2 ohms vs 31.5 ohms, p less than 0.005). Non-smokers had significantly higher mean concentration of 6-keto-prostaglandin-F1-alpha than smokers (109.8 pmol/l vs 92.3 pmol/l, p less than 0.05). The level of thromboxane B2 did not differ significantly between the two groups. These observations suggest that the role of smoking as a risk factor for ischaemic heart disease is unlikely to be related to a direct enhancement of aggregation. On the contrary, the observations seem to suggest that habitual smoking may directly reduce platelet aggregability.

Parity as a determinant of the hematologic response to hematinics supplementation in underprivileged pregnant women in Malaysia.

The effect of parity on the hematological response to supplemental hematinics and the relationship between birth weight and Hb concentration were examined in 67 pregnant rural Kelantanese Malay women recruited at 20-24 weeks of gestation. Among initially anemic women (Hb concentration at recruitment < 110 g/l), a significant supplementation effect was observed in the lower parae (3 or less children) but not in the higher parae. Among initially nonanemic women, a progressive decline in mean Hb concentration was observed in the higher parae; in the lower parae, however, an initial fall in mean Hb concentration was followed by a rise to almost the initial level. Birth weight was inversely related to initial Hb concentration. There was no association between birth weight and final measured Hb level, parity or any of the measured maternal characteristics. These observations suggest: a) women with initially lower Hb concentration might have experienced a greater acceleration of plasma volume expansion than those with initially higher Hb level; and b) hemopoiesis might be impaired in the higher multiparae.

Hookworm infection and protein-energy malnutrition: transverse evidence from two Malaysian ecological groups.

Anthropometric and parasitological data from cross-sectional studies of two groups of primary school children (Group I of Indian origin, 325 boys and 259 girls, age = 7 years; Group II of Malay origin, 284 boys and 335 girls, age = 7-9 years) from two different ecological settings in Peninsular Malaysia were examined for epidemiological evidence of an association between hookworm infection and protein-energy malnutrition. In both ecological groups, significant weight, height and haemoglobin deficits were observed in children with hookworm infection after adjustment for covariables including Ascaris and Trichuris infection intensities and other child and family characteristics. The deficits were related to the intensity of infection based on egg counts. These findings suggest that hookworm may be an important determinant of chronic protein-energy malnutrition, as well as anaemia, in areas where diets are generally inadequate in protein, energy, and iron. Well-controlled intervention studies are needed to confirm these observations.

Fluoride studies in Malaysia.

Twenty-four-hour urine samples and whole deciduous teeth from fluoridated (0.71 ppm) and non-fluoridated (0.14 ppm) areas together with some selected local food items were analysed for their fluoride content. The mean values for urinary fluoride were 0.90 ppm or 0.77 mg per day for the fluoridated area and 0.50 ppm or 0.52 mg per day for the non-fluoridated area. Assuming that half of all the fluoride ingested is excreted in the urine, this study suggests that the average daily fluoride intakes by adults in the fluoridated and non-fluoridated areas were about 1.5 mg and 1 mg respectively. The mean fluoride content of non-carious deciduous teeth from the fluoridated area was 416.89 ppm compared to 178.45 ppm in the low fluoride area.