Vitamin A: is it a risk factor for osteoporosis and bone fracture?

Results from observational studies of the association between vitamin A intake or serum concentration and bone mineral density or fracture are mixed. The inconsistencies may be due, in part, to difficulties in obtaining an accurate assessment of vitamin A intake or status. Serum retinol is a poor measure of vitamin A status because it is subject to homeostatic control. Stable-isotope-dilution methodology gives a validated assessment of the total-body and liver vitamin A stores and is recommended in future studies on vitamin A status and osteoporosis. The potential for exacerbating an already serious public health problem with intakes of vitamin A currently considered safe indicates further research into this matter is warranted.     

Hypothesis: is lactose a dietary risk factor for ischaemic heart disease?

The prevalence of primary adult lactose malabsorption (LM) in 23 ethnic groups was matched with national data on milk consumption and mortality rates from ischaemic heart disease (HD). In 6 other ethnic groups prevalence of LM was related to unquantified assessments of milk consumption and frequency of IHD. On the available data, populations with a prevalence of LM over 30%, and whose consumption of milk is low or is largely in low lactose form, have a lower risk of IHD mortality than populations with a prevalence of LM under 30% and a high milk consumption. There is evidence against attributing these findings to genetic linkage between susceptibility to IHD mortality and persistent lactose absorption, or to differences in socio-economic development, cigarette consumption or intake of animal fats. The findings are compatible with an hypothesis that, if the correlation reported previously between milk consumption and IHD mortality is causal, lactose could be the responsible dietary factor.     

Dietary sodium as a risk factor for osteoporosis: where is the evidence?

Na-induced calciuria has been well documented and provides a physiological basis for the proposed role of dietary Na (or salt) as a risk factor for osteoporosis. However, the evidence is based primarily on acute salt-loading studies, and there are insufficient data on the effects of high salt intake on net Ca retention to predict long-term effects on bone health. Results of investigations on salt and bone turnover, as assessed by bone biomarkers, are inconsistent, but the large variations in inter-individual response to acute and chronic Na loading may be related to salt sensitivity. Results of cross-sectional and prospective investigations on high salt intake and long-term bone health are inconclusive, probably reflecting the difficulty of conducting such studies in free-living populations. However, the mean urinary Ca loss of 1 mmol/100 mmol Na suggests that chronic changes in salt intake may have large effects on Ca and bone balance, especially in individuals with a reduced capacity to compensate for Na-induced Ca loss. Investigating the relationship between salt intake and bone health requires a greater focus on whole diets (including components such as K, Mg, P and protein), reliable measures of salt intake, appropriate bone health outcome measures, and improved subject characterisation (e.g. salt sensitivity). The reasons for inter-individual variability should be explored using post-genomic techniques.     

Mild dehydration: a risk factor for dental disease?

A review of the published international literature was undertaken to investigate whether dehydration is a risk factor for dental disease. Published evidence of associations between saliva and dental disease and between saliva and dehydration was observed, but the precise nature of these associations is unclear and no evidence of a direct link between dehydration and dental disease was found. It is concluded that no direct link between dehydration and dental disease has been proven, although there is considerable circumstantial evidence to indicate that such a link exists.     

Recreational drug use: a major risk factor for gastroschisis?

The authors tested the hypothesis that the birth prevalence of gastroschisis is positively associated with use of recreational drugs in early pregnancy. A matched case-control study was carried out in three regions of the United Kingdom over the period January 2001 through August 2003. For each case, three liveborn controls were matched by initial intended place of delivery, region, and maternal age. Maternal hair analysis provided independent verification of recreational drug use. Conditional logistic regression was used to estimate mutually adjusted odds ratios. Estimates were revised using data from hair analysis. Statistically significant adjusted odds ratios for gastroschisis were associated with first-trimester use of 1) any recreational drug (odds ratio (OR) = 2.2, 95% confidence interval (CI): 1.2, 4.3) and 2) vasoconstrictive recreational drugs (defined as cocaine, amphetamines, and ecstasy) (OR = 3.3, 95% CI: 1.0, 10.5). Other significant exposures included aspirin use (OR = 20.4, 95% CI: 2.2, 191.5), cigarette smoking (OR = 1.7, 95% CI: 1.1, 2.6), and prior history of gynecologic infection/disease (OR = 2.6, 95% CI: 1.2, 5.6). Recreational drug use is a significant risk factor for gastroschisis and is one of a constellation of potentially preventable exposures which include cigarette smoking, aspirin use, and history of gynecologic infection/disease. Maternal hair analysis proved an acceptable and valuable method of independently verifying recreational drug use.     

Medical futility in pediatrics: is it time for a public policy?

For the past decade, there has been a debate raging within the medical, ethical, and legal communities focusing on the issue of medical futility. What has fueled the fires of this multi-faceted debate is the patient rights movement and the perception that the right to self-determination extends not only to the refusal of medical treatments but to demands for overtreatment. The medical specialities of Pediatrics and Neonatology further complicate this issue because despite the dramatic technological advances in these areas, diagnostic and prognostic certainty for many medical conditions remains illusive. As a result, surrogates have to decide whether children with various congenital anomalies, diseases, and genetic defects should be treated aggressively if at all. This uncertainty has led to conflicts between physicians and families about whether certain medical treatments are futile and thus not in the best interest of the child. From a legal and ethical perspective, one way to resolve these conflicts would be a specific process-based public policy approach to futility determinations on a case-by-case basis. The medical futility policy proposed as a public policy protects the patient's right to self-determination; the physician's right of professional integrity; society's concern for the just allocation of scarce medical resources; and is securely rooted in the ethical tradition of promoting and defending human dignity.     

Is restrained eating a risk factor for weight gain in a general population?

BACKGROUND: In modern societies characterized by abundant and accessible foods, restrained eating may become an adaptive behavior to limit weight gain. OBJECTIVE: We assessed the relations between eating behavior (EB) and adiposity in a general population over a 2-y period. DESIGN: We recruited 466 adults and 271 adolescents in 1999 on a geographical basis to participate in a longitudinal study. At the initial examination and 2 y later, they answered an EB questionnaire, the Three-Factor Eating Questionnaire-R18, which measured cognitive restraint (CR), uncontrolled eating, and emotional eating. On the same occasions, several measures of adiposity were also obtained: body mass index (BMI; in kg/m2), waist circumference, the sum of 4 skinfold thicknesses, and percentage body fat. Relations between EB and adiposity were tested separately in adults and adolescents by using mixed linear regressions after adjustment for age, sex, and (in adolescents) Tanner pubertal stage. RESULTS: At baseline, CR was positively associated with BMI in normal-weight subjects (mean BMI: 21.4 in the lowest to 23.3 in the highest CR quintile; P < 0.001) but not in overweight adults (P = 0.25). Initial CR did not predict change in adiposity variables (BMI change: P = 0.79 in adults, P = 0.57 in adolescents and young adults). Conversely, a high initial BMI was associated with a larger increase in CR (beta = 20.1, P < 0.0001 in adults; beta = 21.7, P = 0.003 in adolescents and young adults). CONCLUSIONS: Restrained eating is strongly associated with adiposity in normal-weight subjects but not in overweight subjects. However, restrained eating does not promote weight gain.     

Is zinc deficiency a risk factor for atherosclerosis?

The development of atherosclerosis is influenced by genetic, lifestyle and nutritional risk factors. Zn and metallothionein deficiency can enhance oxidative-stress-related signalling processes in endothelial cells, and since changes in available plasma Zn may affect the Zn status of the endothelium, Zn deficiency could be a risk factor for IHD. Although the association of Zn with many proteins is essential for their function, three key signalling processes are highlighted as being principal targets for the effect of Zn deficiency: the activation of NF-kappaB, the activation of caspase enzymes and the signalling of NO. The need to develop a reliable indicator of Zn status is critical to any epidemiological approach for studying the relationship between Zn status and disease incidence. Studies using appropriate animal models and investigating how the plasma Zn pool influences endothelial intracellular labile Zn would be helpful in appreciating the importance of Zn deficiency in atherogenesis.     

Suicide and marital status in the United States, 1991-1996: is widowhood a risk factor?

OBJECTIVES: This study examined whether marital status is associated with suicide rates among various age, sex, and racial groups, in particular with widowhood among young adults of both sexes. METHODS: US national suicide mortality data were compiled for the years 1991-1996, and suicide rates were broken down by race, 5-year age groups, sex, and marital status. RESULTS: Data on suicide rates indicated an approximately 17-fold increase among young widowed White men (aged 20-34 years), a 9-fold increase among young widowed African American men, and lesser increases among young widowed White women compared with their married counterparts. CONCLUSIONS: National data suggest that as many as 1 in 400 White and African American widowed men aged 20-35 years will die by suicide in any given year (compared with 1 in 9000 married men in the general population).     

Is hypercholesterolemia a risk factor and should it be treated in the elderly?

PURPOSE: The 1993 National Cholesterol Education Program guidelines recommend cholesterol screening for elderly patients with and without known coronary heart disease. This review summarizes clinical trial evidence from the medical literature that addresses cholesterol treatment in the elderly. DATA SOURCES: References were obtained from a MEDLINE search, bibliographies, metaanalyses, and review articles. STUDY INCLUSION AND EXCLUSION CRITERIA: Randomized, controlled clinical trials, including all lipid intervention trials with elderly participants or subgroup analyses of the elderly designed to measure major cardiovascular disease endpoints, were selected. DATA EXTRACTION METHODS: A MEDLINE search of all clinical trials using key search terms yielded 1360 references. Journal titles and abstracts were reviewed for all references by one of us (K.M.H.). A full journal review was undertaken for 41 references to clinical trials. Five clinical trials fulfilled all criteria and represented unique data. DATA SYNTHESIS: A MEDLINE search (from 1966 to January 2000) and bibliography reviews yielded five important clinical trials with analyses of elderly participants. Data are presented in text form and a summary table. MAJOR CONCLUSIONS: Clinical trial evidence supports treating hyperlipidemia in elderly persons for secondary prevention of coronary heart disease. Evidence from four secondary prevention trials demonstrated that major coronary heart disease risk decreased by 25% to 30% in elderly subjects treated for 5 years. Unanswered questions include cholesterol treatment for primary prevention in the elderly, gender effect, and benefit of treatment in persons older than 70.