Mohammad Mostafa Zaman

Reporting of attributable and relative risks, 1966–97

Evidence-based medicine has excited health-care professionals. It applies to clinical and public-health settings, which need different problem analyses. The goal of public health is to decrease or prevent diseases in the population. Relative risks (RR) and odds ratios (OR) estimate the strength of association between diseases and risk factors; whereas attributable risk (AR) estimates the amount of disease attributable to a certain factor. A risk factor may be strongly related to a disease, but may contribute less to the problem of that disease in the population if its prevalence is low (low AR). Conversely, a risk factor with a weak association may contribute more if its prevalence is high (high AR). Control of the latter factor would reduce burden of disease in the population more effectively than control of the former. AR can link causality with public health action. AR can be best derived from cohort studies; its estimation from case-control studies is also possible if controls represent the general population. Despite repeated advocacy of its importance for public health, AR has received less attention than RR. We counted the number of papers reporting RR with AR which appeared on MEDLINE from January, 1966, to January, 1998. The “Textword” procedure was used in searching for: “relative risk” or “odds ratio” for retrieving articles with RR or OR, and “attributable risk”, “attributable fraction”, or “aetiological fraction” for articles with AR. There was one report with AR for 31 with RR

Population Attributable Fraction of Stroke Incidence in Middle-Aged and Elderly People: Contributions of Hypertension, Smoking and Atrial Fibrillation

We determined the population attributable fraction (PAF) of stroke due to hypertension (HT), atrial fibrillation (Af) and smoking in a Japanese community. Residents of Shibata (n = 2,302) who were surveyed initially in 1977 were followed until 1997. Two hundred and thirteen first strokes occurred. Among those 40–64 years of age, the risk ratio (RR) of Af was 11.24, followed by untreated HT (3.61), uncontrolled HT (3.69) and smoking (1.84). The PAFs, however, were 14.9% for smoking, 13.5% for untreated HT, 8.6% for uncontrolled HT and 3.6% for Af. Among those over 65 years, only Af was significant (RR 3.89) and the PAF was 6.0%. Determination of PAFs is also essential for designing effective stroke prevention programs in communities.

Nutritional factors associated with rheumatic fever.

The determinants for a child with group A beta-haemolytic streptococcal throat infection (BHS infection) to develop rheumatic fever (RF) remain unclear. In this case-control study, we deal with BHS infected children to examine whether nutritional factors are related to RF. In a RF hospital in Dhaka (Bangladesh) we examined 218 consecutive out-patients who had antecedent BHS infection. Sixty of them met the updated Jones criteria for RF (cases) while 104 did not (controls). Fifty-four possible RF patients were excluded. We used anthropometric measurements and a food frequency questionnaire to assess nutritional factors. Higher risk of RF was observed for low height for age (odds ratio 3.82, 95% confidence interval 1.73-8.42); low weight for age (2.41, 1.12-5.57); low upper arm circumference for age (3.76, 1.87-7.89); and low consumption of eggs (3.81, 1.95-7.63), milk (2.60, 1.36-5.08), chicken (2.62, 1.35-5.21), pulses (1.98, 1.03-3.84), fruits 2.29, 1.20-4.45), and ruti (home-made bread) (3.15, 1.61-6.34). Reduced risk was observed for soybean oil consumption (0.28, 0.12-0.62). The significant association of upper arm circumference and eggs persisted after adjustment for multiple sociodemographic confounders. The association of ruti and soybean oil appeared to be suggestive (0.05 < p < 0.1). Protein-energy malnutrition is likely to be associated with RF. The protective effect of moderate consumption of eggs and soybean oil may support other published work which suggests that the anti-inflammatory substance present in these food items may prevent maturation of the rheumatic process.