The design of family studies to estimate the value of an intraclass correlation coefficient p is considered when ni individuals are to be selected from each of k families, i = 1, 2, ..., k. In particular, the accuracy of a balance design (ni = n, i = 1, 2, ..., k) for estimating p is compared with the accuracy of an unbalanced "natural" design, in which the ni are sampled at random from family size distributions that tend to occur in practice. It is found for two different estimators of p that the balanced design is usually preferable, but only to a small degree if the number of families sampled is greater than 50.
Author reply to: Chia CP. Low birth weight babies. Med J Malaysia. 1995 Mar;50(1):120.
Comment on: Yadav H. Low birth weight incidence in Lundu, Sarawak. Med J Malaysia. 1994 Jun;49(2):164-8.
No population-based cancer registry exists in Malaysia; thus our main sources of incidence data were biopsy series. We determined the frequency of cancers by body site, sex, and ethnic group from biopsy records of the Division of Pathology of the Institute for Medical Research in Kuala Lumpur for the years 1969-71. We then made comparisons of leading sites with data from the Singapore Cancer Registry. Relative risk values for 21 sites indicated significant differences among ethnic groups for cancers of the nasopharynx, larynx, lung, bone, skin, cervix, ovary, prostate, and penis and for lymphomas.
To investigate the association between regular coffee consumption and the prevalence of coronary artery calcium (CAC) in a large sample of young and middle-aged asymptomatic men and women.
Lack of awareness of signs and symptoms and risk factors of oral cancer can lead to late presentation of the disease that contributes to poor survival of patients who contract it. This study aims to determine the level of awareness regarding oral cancer in adult patients attending School of Dental Sciences, Universiti Sains Malaysia.
A survey was conducted to investigate the prevalence of Enterobius vermicularis in 1352 Chinese children between the ages of 6-12 years from the three National Type Chinese Primary Schools in Pulau Ketam in 1988, using the scotch-tape technique on three successive days. The overall prevalence was high (56.88%). The prevalence in Sin Bin School was significantly lower (50.86%) compared to the other two schools (56.60% and 61.04%). Prevalence was significantly higher amongst the 6-7 years age group (61.61%-70.18%) compared to other age groups (47.9%-59.29%). There was no difference in the prevalence between the boys and girls being 56.15% and 57.55% respectively.
Analysis of mothers' recall data collected in 1976-1977 by a probability survey in Peninsular Malaysia shows an association between breastfeeding up to six months of age and improved survival of infants throughout the first year of life. Inappropriate sample selection and inadequate control of confounding can introduce large biases in these analyses. The magnitude and direction of these biases are presented. Even when these biases are dealt with, unsupplemented breastfeeding appears more beneficial than supplemented breastfeeding. The younger the infant and the longer the breastfeeding, the greater the estimated benefits in terms of deaths averted. The use of powdered infant formula did not appear to offset the detrimental effects of early weaning and supplementation. The positive relationships found in these analyses between breastfeeding and survival are not due to death precluding or terminating breastfeeding. Nor are they likely to be due to a shift away from breastfeeding because of recent illness, which was also controlled in the analyses. Nor are they likely to be due to other factors that both increase mortality risk and shorten breastfeeding; when such factors are taken into account, the beneficial effects of breastfeeding become stronger and imply that, if there had been no breastfeeding in this sample, twice as many babies would have died after the first week of life.
Being a rapidly developing country, a study was needed to see how we faired in treating head and neck cancer patients compared with international standards. Although being a retrospective study, this research shows that there is still a lot to be done in our developing nation in educating the general public about head and neck cancers as most of them presented in the later stages to us. There also needs to be a proper review about the treatment modality offered to patient as our survival results are far behind in certain categories of cancers compared with the developed nations.
One of the objectives of this short communication was to add to the literature on the prevalence of oral recurrent aphthous stomatitis (ORAS). This research is based on a total of 11,697 randomly selected Malaysian subjects with an age range of 25-115 years and a mean age of 44.5 +/- 13.9 years who were examined for oral mucosal lesions (ORAS). The prevalence of ORAS detected during the oral examination (average point prevalence) was found to be 0.5% (64 subjects). ORAS formed 5.7% of all lesions detected during the survey. The average point prevalence of ORAS was highest in the indigenous people of Sabah and Sarawak (1.2%), followed by the Chinese (0.7%), the Malays (0.5%) and the Indians (0.1%). This difference was statistically significant (p < 0.001). A review of the English literature on the prevalence of ORAS revealed different prevalence types used by different researchers, namely average point prevalence (APP), self reported life-time prevalence (SLP) and self reported two-year prevalence (STP). The other objective of this paper was to present the different types of prevalence that have been reported in the literature and to discuss the usefulness of such prevalence types in relation to using epidemiology in deriving certain possible etiological associations.
Insecticide-impregnated bed nets act as a physical barrier to repel and kill mosquitos. Community intervention trials suggest that these nets are effective in preventing malaria-related mortality and morbidity--but not malaria infection--in areas of low and moderate transmission; the results from areas of high transmission are not so encouraging. Comparison of the results from these trials and their interpretation are difficult because of variations in the epidemiology of malaria and several methodological flaws. Problems such as defining appropriate health indicators, monitoring bed-net usage, introducing bed nets randomly, selecting adequate controls, performing statistical analysis, and comparing bed nets with other available interventions are considered. Further community intervention trials are needed, paying attention to the methods and to assessment of their impact on malaria.
Quantitative understanding of the transmission dynamics of lymphatic filarial parasites is essential for the rational planning of control strategies. One of the most important determinants of transmission dynamics is the relationship between parasite yield, the success rate of ingested microfilariae (mf) becoming infective larvae in a mosquito vector, and mf density in the source of the human blood meal. Three types of relationship have been recognized in human filaria/mosquito couples--limitation, facilitation and proportionality; facilitation has hitherto been observed only in the couple Wuchereria bancrofti/Anopheles gambiae in Burkina Faso, in experimental studies on a high density mf carrier. The present paper demonstrates facilitation in W. bancrofti/An. gambiae and W. bancrofti/An. arabiensis in lower mf density carriers in The Gambia and Tanzania, and in W. bancrofti/An. funestus in Tanzania. Facilitation was not found in An. melas in The Gambia nor in An. merus in Tanzania. Analysis of published data shows limitation at low level mf densities in W. bancrofti/Culex quinquefasciatus in Sri Lanka, and in the same couple in India. Limitation also occurs in Brugia malayi/Aedes togoi in experimental cats; proportionality occurs in B. malayi/Mansonia bonneae in Malaysia. The epidemiological significance of these host/parasite relationships is discussed, and supporting evidence for its validity is presented from the published results of large-scale control programmes.
In this paper we first present methods and preliminary results of pilot surveys of "serious" mental retardation (IQ less than or equal to 55); the surveys included screening and diagnostic components and were carried out in the less-developed world. Next we discuss two problems raised by these surveys: one is the diagnosis of a case and its clinical dimensions, and the other is the interpretation of prevalence. In the next section we illustrate epidemiological approaches to the analysis of such data, in particular their relevance to prevention. Lastly, we propose that the two-stage survey approach developed in the course of the pilot work can provide a valuable basis for planning and prevention, if certain key conditions can be met.