Risk factors for the transmission of diarrhoea in children: a case-control study in rural Malaysia

In response to a recorded increasing incidence of diarrhoea in Tumpat District, Malaysia, a case-control study was performed to identify modifiable risk factors for the transmission of diarrhoea, in children aged 4-59 months. Ninety-eight pairs of children, matched on age and sex, were recruited prospectively from health centres. Exposure status was determined during a home visit. Interviewers were 'blinded' as to the disease status of each child. Odds ratios were measured through matched pair analysis and conditional logistic regression. Risk factors for diarrhoea identified were: reported--drinking of unboiled water, storage of cooked food before consumption and bottle feeding; and observations--animals inside the house and absence of washing water in latrines. Water quality, source of drinking water, reported hand washing behaviour, indiscriminate defecation by children, cup use and the absence of a functional latrine were not associated with diarrhoea. Nonsignificant associations were found for: accessibility of washing water source, type of water storage container and use of fly covers for food.

Fatal stroke and use of oral contraceptives: findings from a case-control study

A case-control study of women less than 40 years of age in England and Wales was performed to evaluate the risk of fatal stroke associated with the use of the newer, low-dose oral contraceptives. Included were 296 cases with subarachnoid hemorrhage, 105 cases with other hemorrhagic stroke, and 21 cases with occlusive stroke, all of which occurred during 1986-1988. Two living controls per case, matched for age and marital status, were chosen from the general practice lists. The power of the study was such that the minimum significant increased relative risk of subarachnoid hemorrhage associated with ever having used oral contraceptives that could have been detected with 90% certainty was 1.6; the equivalent value for occlusive stroke was 28.4. Relative risk was estimated by conditional logistic regression allowing for matching. The adjusted relative risk of subarachnoid hemorrhage associated with oral contraceptives was estimated to be 1.1 (95% confidence interval (CI) 0.6-1.9) for current use and 1.3 (95% CI 0.9-1.8) for ever use, while the equivalent relative risk of an occlusive stroke associated with ever use was 4.4 (95% CI 0.8-24.4). Oral contraceptive use may be associated with a small increase in the risk of subarachnoid hemorrhage. These data are consistent with a substantial increase in the risk of occlusive stroke associated with oral contraceptive use.

The psychosocial impact of HIV infection in men with haemophilia: controlled investigation and factors associated with psychiatric morbidity

The aim of the investigation was to establish the prevalence of psychosocial problems in men with haemophilia and HIV infection, and to identify factors associated with psychological morbidity. A cross-sectional controlled study including 37 HIV seropositive and 36 HIV seronegative men with haemophilia under the care of the Oxford Haemophilia Centre were included in the investigation. The outcome measures included current psychological status (PSE, POMS, Beck Hopelessness Scale and Self-Esteem) and psychiatric history; coping and health beliefs (Self-Control Schedule, Hardiness Scale, Health Locus of Control Scale); social functioning (Modified Social Adjustment Scale); and sexual functioning. The results showed that seropositive individuals, whether symptomatic or not, had significantly worse total PSE scores and had higher levels of hopelessness. In addition, symptomatics had worse depression scores (POMS) than seronegatives. However, levels of psychiatric morbidity were generally low, even in the seropositive group. High levels of psychological morbidity were associated with high levels of hopelessness, unfavourable social adjustment, past psychiatric history and symptomatic HIV disease. Seropositives reported greater negative impact on their sex lives, and sexually active seropositives reported a significantly greater prevalence of sexual dysfunction than seronegatives. The majority of seropositives reported regular condom use during intercourse, and also continuing concerns about infecting their sexual partners in spite of it. In summary, it was found that men with haemophilia an HIV infection have higher levels of psychological distress and sexual problems than seronegatives. The skilled staff involved in their treatment are in a good position to identify their difficulties and ensure that good care is provided.

Use of nonoxynol-9 and reduction in rate of gonococcal and chlamydial cervical infections

The spermicide nonoxynol-9 (N-9) has been used as a contraceptive for over 30 years, but the use of a vaginal spermicide and condoms for the prevention of sexually transmitted infections has not been examined in randomised studies. We report a single-blind randomised field trial to assess the effect of N-9 film on the rate of gonococcal and chlamydial cervical infection in women at high risk of these diseases. 343 women were randomly assigned to use either condoms and N-9 (186 women) or condoms and a placebo (157). Compliance with condom use was much the same in the two groups. Overall, N-9 reduced the rate of cervical infection by 25% (rate ratio [RR] 0.75, 95% confidence interval [Cl] 0.5-1.1); in women who used N-9 for more than 75% of their coital acts the infection rate was reduced by 40% (RR 95% Cl 0.3-1.0). The rate of yeast vulvovaginitis or genital ulcers was not higher in N-9 users than in placebo users, but the rate of symptomatic irritation was increased by 70% (RR 95% Cl 1.1-2.6) among N-9 users. Condom use was more protective against cervical infection than N-9 use. The rate of infection was 50% (RR 95% Cl 0.3-0.7) lower with 75% than with 0-50% condom compliance. The use of a vaginal N-9 spermicide with condoms whenever possible seems to be a better strategy than the use of condoms only for prevention of gonococcal and chlamydial cervical infection.

Serum and endometrial sodium and potassium levels with inert and copper-containing IUCDs and relation to serum steroid levels

Serum and endometrial sodium (Na) and potassium (K) levels and serum estradiol, progesterone, testosterone and cortisol were measured in the mid-follicular and mid-luteal phases of the menstrual cycle in 20 Lippes loop and 20 CuT-200 IUCD users and 20 matched controls. Na and K were measured by atomic absorption spectrophotometry, while serum steroids were measured by RIA. Regarding steroids, the only significant difference between the three groups was a significantly lower mean mid-luteal serum estradiol in CuT-200 IUCD users compared to Lippes loop users (p less than 0.05). Regarding sodium in the control group, there was significantly lower mean mid-luteal serum and endometrial Na (p less than 0.01) that was not found in both groups of IUCD users. In the mid-follicular phase, there was significantly higher mean serum Na in both Lippes loop and CuT-200 groups compared to controls (p less than 0.05). Mean endometrial Na showed no significant difference between the three groups in both phases of the menstrual cycle. Regarding potassium in the control group, there was significantly lower mean levels in the mid-luteal-phase of the cycle (p less than 0.01) that was not seen with both groups of IUCD users. Serum K showed no significant difference in the three groups in both phases of the menstrual cycle. Endometrial K showed a significantly higher mean level in both Lippes loop and CuT-200 IUCD users compared to controls in the mid-luteal (p less than 0.01), but not in the mid-follicular phases of the cycle.

Hormonal profile of the menstrual cycle in Chinese women after tubal sterilization

Ten women after tubal sterilization were studied for the hormonal profile of the menstrual cycle. They had undergone sterilization procedures, on the average 5.3 years (range 1.5-10 years) earlier. The serum concentrations of LH, FSH, prolactin, estradiol and progesterone were measured by RIA in daily blood samples of a complete menstrual cycle. Another ten normal women were studied at the same time and were used as the control group. There were no significant differences in the hormonal patterns of the menstrual cycle between the two groups. There was a significantly lower LH level in the early luteal phase of the tubal ligation group compared to the control group. Also, a significantly lower E2 luteal peak compared to the preovulatory peak was observed in the tubal ligation group. The physiological significance of these minor changes is not clear. Only one out of ten women in the tubal ligation group, who had undergone sterilization 1.5 years prior, showed a deficiency in luteal function, but her ovulatory function and menstrual cycle appeared normal. This study indicates that normal hormonal profiles are retained after tubal sterilization.

An efficacy trial of a mammalian cell-derived recombinant DNA hepatitis B vaccine in infants born to mothers positive for HBsAg, in Shanghai, China

We conducted a randomized, double-blind clinical trial of an experimental mammalian cell-derived DNA hepatitis B vaccine (Betagen, Connaught Laboratories Ltd, Toronto, Canada) to determine its efficacy in infants born to mothers who were carriers of hepatitis B surface antigen (HBsAg). Four groups of 55 infants received injections as follows: (1) a licensed plasma-derived vaccine (Lanzhou, Lanzhou Institute for Biological Products, Lanzhou, People's Republic of China), 20 micrograms; (2) Betagen, 20 micrograms; (3) Betagen, 20 micrograms+hepatitis B immune globulin (HBIG); and (4) Betagen, 10 micrograms+HBIG. Vaccine injections were given at birth and at 1 and 6 months and HBIG was given at birth. The vaccines were compared to a historical placebo control group. The efficacy of Betagen alone was 82.6% compared to 51.0% for the Lanzhou. Efficacy of Betagen increased with the concomitant use of HBIG. No infants who were HBsAg negative at birth and/or were born to hepatitis B e antigen (HBeAg) negative mothers became carriers. The rate of HBsAg in infants receiving Betagen alone, and born to mothers who were HBeAg positive, decreased from 60% at birth to 20% by the ninth month, compared to 62.5% and 50% (respectively) for Lanzhou. The percentage of infants with protective levels of antiHBs was significantly higher for Betagen alone than for Lanzhou, but the geometric mean titre of antiHBs for responders was not significantly different. We have shown that Betagen alone is highly efficacious in preventing the development of hepatitis B in infants born to mothers who are carriers of HBsAg and is also highly effective in reducing the carriage of HBsAg in infants who are HBsAg positive at birth and/or born to HBeAg positive mothers.

The effects of a combined contraceptive vaginal ring releasing ethinyloestradiol and 3-ketodesogestrel on vaginal flora

Fifty nine women with documented normal ovulatory cycles and with no symptoms of vaginal infection were divided into four groups. Each group used a combined contraceptive vaginal ring (CCVR) with a mean daily release rate of 0.015 mg of ethinyloestradiol (EE) and 0.120 mg of 3-ketodesogestrel (3-KDG) per day, for one cycle of either 21, 28, 42, or 56 days. Cultures from the posterior vaginal fornix and from the endocervical canal were obtained immediately before insertion of the ring and on removal of the ring. Changes in the numbers of vaginal cells, aerobic and anaerobic bacteria, Chlamydia trachomatis, Gardnerella vaginalis, yeasts and Trichomonas vaginalis were documented at the end of each treatment. Intra- and inter- group changes in the vaginal flora were assessed at the end of each treatment. The comparison between the number and type of flora showed no significant change between the pre-treatment population and the post-treatment population. The results of this study suggest that the use of this CCVR for 21, 28, 42 and 56 days is not associated with an increase in inflammatory cells or pathogenic bacteria.

Hygiene habits and carriers in families with a child who has had typhoid fever

The relationship between asymptomatic shedding of bacterial enteropathogens and the hygiene habits of families who have had a child with typhoid fever (TF) are investigated. The sample was made up of 80 families: 40 families in which one child had had TF (Group A) and 40 in which no children or either of the parents had had a history of TF (Group B). In each group 20 families belonged to a low socioeconomic status (SES) and 20 to a high SES. A structured interview was used to evaluate the SES and the hygiene habits of the child; observations were made to measure the hygiene habits of the family (toilet, kitchen and food preparation) and bacteriological studies (fecal samples and hand markers). Results show that carriers were more frequent in Group A than in Group B. The bacterial species found were significantly more numerous in Group A than in Group B (fecal samples: E. coli, the classic serotypes, Shigella ssp, and hand markers: E. coli). Families of Group A had higher carriage rates than those of Group B. Finally there exists a significantly higher association between inadequate hygiene habits and carrier families. These results show the need to teach specific habits of proper hygiene to the entire population, because the fact of belonging to the high SES does not in itself preclude inadequate hygiene habits.

A prospective treatment study of premenstrual symptoms using a triphasic oral contraceptive

Eighty-two women with complaints of moderate to severe premenstrual symptoms were recruited for a double-blind, controlled trial of a triphasic oral contraceptive (o.c.). Subjects made daily ratings of symptoms for at least one baseline cycle and were then randomly assigned to receive either placebo or o.c. for three months. Twenty-three women dropped out of the study (18 o.c., 5 placebo), 13 failed to show prospective confirmation of moderate to severe premenstrual symptoms, and one placebo subject had an anovulatory cycle. Forty-five women with prospectively-confirmed premenstrual changes (20 o.c., 25 placebo) completed the study. Premenstrual breast pain and bloating were significantly reduced with active treatment compared to placebo (p less than 0.03) but there were no beneficial effects of the o.c. over placebo for any of the mood symptoms. Women who received o.c.s reported decreased sexual interest after starting treatment and this effect was independent of any adverse influence on mood.

Incidence of disease after vasectomy: a record linkage retrospective cohort study

OBJECTIVE

To determine whether vasectomy is associated with an increased risk of several diseases, and in particular testicular cancer, after operation.

DESIGN

Retrospective cohort study using linked medical record abstracts.

SETTING

Six health districts in Oxford region.

SUBJECTS

13,246 men aged 25-49 years who had undergone vasectomy between 1970 and 1986, and 22,196 comparison subjects who had been admitted during the same period for one of three specified elective operations, appendicitis, or injuries.

MAIN OUTCOME MEASURES

Hospital admission and death after vasectomy or comparison event.

RESULTS

The mean durations of follow up were 6.6 years for men with a vasectomy and 7.5 years for men with a comparison condition. The relative risk of cancer of the testis in the vasectomy cohort (4 cases) compared with that in the other cohorts (17 cases) was 0.46 (95% confidence interval 0.1 to 1.4), that of cancer of the prostate (1 v 5 cases) 0.44 (0.1 to 4.0), and that of myocardial infarction (97 v 226 cases) 1.00 (0.8 to 1.3). There was no evidence of an increase associated with vasectomy in the incidence of a range of other diseases.

CONCLUSIONS

Vasectomy was not associated with an increased risk of testicular cancer or the other diseases studied. With respect to prostatic cancer, while we found no cause for concern, longer periods of observation on large numbers of men are required.

Diarrheal disease in Cambodian children at a camp in Thailand

The etiology of acute diarrhea (less than or equal to 3 days duration) and persistent diarrhea (greater than or equal to 14 days duration) was determined in Cambodian children under age 5 years in a refugee camp on the Thai-Cambodian border between May and October 1989; potential risk factors associated with persistent diarrhea were examined in an age-matched case-control study. Specimens collected from children and environmental sources were examined by standard microbiologic methods; Escherichia coli isolates were examined for hybridization with specific DNA probes and in tissue culture adherence assays. The same bacterial, viral, or parasitic agents were identified in 79 children with persistent diarrhea and in 408 children with acute diarrhea. Only one of nine children with persistent diarrhea excreted the same organism, Cryptosporidium, for that extended period. The most important risk factors identified for developing persistent diarrhea were living with other young children (odds ratio (OR) = 2.0, 95% confidence interval (Cl) 1.2-3.4) and being undernourished (OR = 2.6, 95% Cl 1.2-5.7). Persistent diarrhea in children in this camp was associated with several different agents rather than persistent infections with a single organism.

Escherichia coli associated with acute measles and diarrhoea at Kenyatta National Hospital, Kenya

Three hundred and three children under 5 years old with acute measles and diarrhoea (cases) and 300 other age-matched children with diarrhoea (controls) were examined for enteroadherent E. coli (EAEC) and other agents including rotavirus and Cryptosporidium. EAEC was determined by tissue culture of HEP-2 cells. Other agents were determined by conventional methods. EAEC was identified from both cases and control accounting for 10.3% (31/303) and 15.2% (46/300) respectively. Other bacterial agents were: 10.3% (31/303) from cases and 12.8% (39/300) from controls. A higher detection rate of enteroparasites was found among cases 15% (45/300) than controls 8.9% (27/300) whereas rotavirus was the reverse, 3% (9/303) in cases and 30.3% (92/300) in controls. To our knowledge characterization of EAEC has not been done before and therefore might be attributing factor to some of our unexplained diarrhoeal cases.

Post-tubal sterilization syndrome

This article presents a review of the literature on post-tubal sterilization syndrome. Although studies have shortcomings they suggest the majority of women undergoing tubal sterilization do not experience changes in menstrual patterns after the procedure, but a minority do. Suggestions are made for further research, conducted from a nursing perspective. Implications for practice are suggested, given the tentative information on post-tubal sterilization syndrome.

The prevalence of invasive amebiasis is not increased in patients with AIDS

OBJECTIVE

To determine whether the frequency or severity of invasive amebiasis is increased in patients with AIDS.

DESIGN

A case-control sampling approach, based on an autopsy registry.

SETTING

General Hospital of Mexico City, Mexico, a large government-supported, tertiary care medical institution.

PATIENTS, PARTICIPANTS

Ninety-four patients with AIDS and 335 historical and contemporary, age- and sex-matched controls who were defined as dying, but not because of AIDS.

RESULTS

The odds ratio (OR) for mortality from invasive amebiasis was the same for cases and controls (0.7; 95% confidence interval, 0.07-7.2). By contrast, the OR for other diseases, such as miliary tuberculosis, cytomegalovirus infection, Pneumocystis carinii pneumonia and toxoplasmosis was greatly increased. Only one patient with AIDS had amebiasis of the common amebic ulcerative colitis type, without extraintestinal involvement.

CONCLUSION

In conclusion, we show that the frequency and severity of invasive amebiasis is not increased in Mexican patients with AIDS.

Season of birth: issues, approaches and findings for autism

Rates of birth in the general population show seasonal fluctuations for reasons that are ill understood. Variations from these general population patterns have been reported for several psychiatric conditions and used as the basis for aetiological hypotheses. In this paper, the evidence for alterations in the expected seasonal fluctuation in birth dates of autistic people is evaluated. A national sample of 1435 autistic individuals and a clinic sample of 196 subjects are compared to general population figures and to 121 sibling controls. Compared with the general population, the national sample showed significant deviations from the expected rate of birth by month. In the clinic sample, differences from the anticipated monthly pattern were only evident when this sample was compared to the sibling controls. A variety of models for seasonal trends, including year quarters, temperature and sine wave forms, were fitted to these variations but no consistent picture emerged.

Epidemic poliomyelitis in The Gambia following the control of poliomyelitis as an endemic disease. II. Clinical efficacy of trivalent oral polio vaccine

An epidemic of poliomyelitis caused by poliovirus type 1 occurred in The Gambia from May to November 1986. Descriptive findings and vaccination coverage levels are reported in part I. This article (part II) describes a case-control study to estimate the clinical efficacy of three or more doses of trivalent oral polio vaccine compared with zero doses. "Cases" were 1- to 7-year-old children paralyzed during the epidemic who were diagnosed as having poliomyelitis by designated referral physicians. They were identified by reports from referral physicians during the epidemic and by a nationwide village-to-village search after the epidemic. Up to five controls were randomly selected for each case from among children of the same age and sex living in neighboring households. In a matched analysis of 195 cases and 839 controls, the efficacy of three or more doses of trivalent oral polio vaccine was 72% (95% confidence interval 57-82) when children without vaccination cards were considered unvaccinated. The efficacy of three or more doses in 1- to 2-year-old children, in whom the determination of vaccination status was considered to be more accurate than in older children, was 81% (95% confidence interval 66-90). Vaccine failure was not associated with short intervals between doses. Higher levels of vaccination coverage and efficacy than those achieved in The Gambia may be needed in African countries to prevent the return of poliomyelitis as an epidemic disease after it has been controlled as an endemic disease.

Risk factors for epithelial ovarian cancer in Beijing, China

A study in Beijing, China of 112 pathologically confirmed epithelial ovarian cancer cases and 224 age-matched community controls enabled evaluation of risk in relation to reproductive, medical, familial, and selected lifestyle factors. An inverse relationship was observed between the number of full-term pregnancies and ovarian cancer risk. Compared to nulliparous women, subjects with one, two, or three full-term pregnancies were at 50%, 70%, or 90% reduced risks, respectively (P for trend less than 0.01). A positive correlation was found between the number of ovulatory years and risk, with a 2.6-fold increased risk for women with 30 or more compared to less than 10 ovulatory years (P for trend less than 0.01). Infertility, as estimated in various ways, was also found to be an important risk factor. When parity was taken into account, age at first pregnancy was not related to ovarian cancer risk. No protective effect was associated with mumps virus infection. In contrast, risk increased significantly as serum mumps virus antibody titres increased (P for trend less than 0.01). An elevated risk was found in women with a history of long-term (greater than 3 months) application of talc-containing dusting powder to the lower abdomen and perineum (Relative risk 3.9, 95% confidence interval: 0.9-10.63). These findings suggest that Chinese women have risk factors similar to those of occidental women.

Risk factors for breast cancer in women undergoing mammography

To determine risk factors for carcinoma of the breast, we compared women with cancer on screening and diagnostic mammography with those in whom cancer was not detected. For 39 months, medical histories were collected by mammography technologists on 3492 women having routine screenings or diagnostic mammograms at our institution. Potential risk factors of women with biopsy-proved breast cancer were compared with those in women who had normal findings on mammograms or negative biopsy results (control subjects). Of the 3492 women, 49 had biopsy-proved breast cancer. There were 3361 patients in the control group, including those women with normal findings on mammograms (3294) and those with negative biopsy results (67). Eighty-two women had incomplete questionnaires or were lost to follow up. Nearly all of the patients with breast cancer were postmenopausal compared with 68% of the control subjects. The mean length of lactation for breast cancer patients was significantly less than for control subjects: 5.6 vs 7.5 weeks (p = .015). This was true also for the postmenopausal patients: 8.1 vs 6.1 weeks (p = .041). Postmenopausal breast cancer patients had menstruated significantly more years (p = .016) than the postmenopausal control subjects: 34 vs 31 years, although the mean age at menarche was not different. When corrected for age, there was no significant difference in the total duration of menstruation in the postmenopausal cancer patients compared with the postmenopausal control subjects. Postmenopausal breast cancer patients had a significantly greater (p = .021) average body weight than postmenopausal control subjects: 71.7 vs 66.7 kg, although body weight was the same when all patients were considered. Similar results were found when Quetelet's index for obesity (weight in kg/height in cm2) (p = .004) was calculated for postmenopausal patients: 28 for cancer patients and 26 for control subjects. There was no significant difference in height between the cancer patients and control subjects when all patients or just the postmenopausal patients were considered. History of oral contraceptive use was significantly less common among postmenopausal breast cancer patients than among postmenopausal control subjects: 9% vs 20%. Patients with breast cancer had lower parity than the control subjects. In our series of patients, women in whom breast cancer was detected on mammography lactated less, showed no significant difference in years of menstruation when corrected for age, had a greater average body weight, used oral contraceptives less often, and had fewer children than women in whom no cancer was detected on mammography.

Childhood mortality after a high dose of vitamin A in a high risk population

OBJECTIVES

To determine whether a single high dose of vitamin A given to all children in communities with high mortality and malnutrition could affect mortality and to assess whether periodic community wide supplementation could be readily incorporated into an ongoing primary health programme.

DESIGN

Opportunistic controlled trial.

SETTING

Jumla district, Nepal.

SUBJECTS

All children aged under 5 years; 3786 in eight subdistricts given single dose of vitamin A and 3411 in remaining eight subdistricts given no supplementation.

MAIN OUTCOME MEASURES

Mortality and cause of death in the five months after supplementation.

RESULTS

Risk of death for children aged 1-59 months in supplemented communities was 26% lower (relative risk 0.74, 95% confidence interval 0.55 to 0.99) than in unsupplemented communities. The reduction in mortality was greatest among children aged 6-11 months: death rate (deaths/1000 child years at risk) was 133.8 in supplemented children and 260.8 in unsupplemented children (relative risk 0.51, 0.30 to 0.89). The death rate from diarrhoea was also reduced (63.5 supplemented v 97.5 unsupplemented; relative risk 0.65, 0.44 to 0.95). The extra cost per death averted was about $11.

CONCLUSION

The results support a role for Vitamin A in increasing child survival. The supplementation programme was readily integrated with the ongoing community health programme at little extra cost.

Risk factors for tubal infertility. Influence of history of prior pelvic inflammatory disease

In order to explore possible etiologic differences between tubal infertility in women who had been physician-diagnosed as having pelvic inflammatory disease ("overt" PID) and in women who had not ("silent" pelvic inflammatory disease), we made use of self-reported data from a large, population-based, case-control study of infertility in King County, Washington. Responses from 33 infertile women with no history of physician-reported PID and 129 infertile women with such a history were compared to those of 501 fertile women. No cultures or blood for antibody titers were obtained. Logistic regression was used to compute the relative risks for silent and overt PID-related tubal dysfunction associated with various lifestyle and contraceptive habits in an effort to identify practices that potentially affect these outcomes. In general, practices associated with an increased risk of overt tubal disease, such as use of Dalkon Shield and other types of intrauterine devices, were also associated with an increased risk of silent tubal disease, but to a lesser extent. Women who used oral contraceptives for longer than three years had a decreased risk for silent disease (relative risk = 0.5, 95% confidence interval = 0.3-0.8), but their risk for overt disease did not decrease to the same extent (relative risk = 0.9, 95% confidence interval = 0.3-2.5). These results suggest that silent and overt tubal disease share many common lifestyle risk factors.

Insecticide-impregnated bed nets for malaria control: a review of the field trials

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.