Birth spacing impacts on preterm delivery
RESEARCHERS have advised doctors to counsel women on the importance of optimal spacing of at least 18 months between births after finding that shorter intervals result in decreased pregnancy length, with more deliveries at all gestational ages prior to 39 weeks, and fewer at 40 weeks and beyond. In a US population-based retrospective study of 454 716 normal, singleton live births to multiparous mothers, published in BJOG, researchers found that 87% followed a normal interpregnancy interval (IPI) of 18 months or more, 10.7% had IPI of 12–18 months and 2.2% were less than 12 months. Following the shortest IPI, 53.3% of women delivered before the 39th week of pregnancy compared with 37.5% of women with a normal IPI. The rate of preterm birth (PTB) before 37 weeks in women with an IPI of less than 12 months was 20.1%, compared with 10.2% for 12–18 months, and 7.7% among women with an optimal IPI. The risk of PTB before 37 weeks for short IPI was increased even after adjustment for coexisting risk factors. The researchers wrote that short IPIs were also associated with a variety of other adverse outcomes, yet despite this knowledge more than a third of pregnancies in the US occurred less than 18 months following a preceding birth. They wrote that a “preponderance” of short IPIs were in women with other high risk factors for preterm birth. “Improvements in optimal birth spacing could result in overall reduction in preterm birth across the world, especially when focused on high risk women in whom short interpregnancy intervals occur most frequently”, they wrote.

Obesity fuelling increased knee replacement rates
A US study finding that the number of total knee replacement (TKR) surgeries more than tripled between 1993 and 2009 has been blamed on the increasing number of overweight and obese Americans. The study, published in the Journal of Bone and Joint Surgery, found a doubling in the number of total hip replacements (THR) during the same period. Researchers reviewed national data on TKR and THR volume, length of hospital stay, inhospital mortality, and orthopaedic workforce trends. They found that the more rapid growth in the use of total knee arthroplasty over total hip arthroplasty was in individuals with a body mass index (BMI) of ≥ 25 kg/m2, which accounted for 95% of the differential increase in TKR over THR volumes. They wrote that changes in hospital and physician reimbursement, length of stay and inhospital mortality did not contribute to this differential growth rate. They also found a disproportionate growth in TKR to THR in patients aged 18–64 years compared with those aged 65 years and older. “The results of this study suggest that rising BMIs have played a substantial role in increasing the demand for total knee arthroplasty over total hip arthroplasty, that younger individuals have been affected to a greater degree, and that the surgical community has responded to this added need primarily by increasing per-physician output”, the researchers wrote. They said the study might prove instructive in understanding and planning for future arthroplasty trends, especially if the prevalence of overweight and obesity continued to increase.

Prophylactic ICD increases survival
THE use of a prophylactic implantable cardioverter-defibrillator (ICD) increases survival at 3 years in patients with heart failure who have a left ventricular ejection fraction (LVEF) between 30% and 35% compared to those with no ICD, according to research published in JAMA. The researchers found that patients with an LVEF less than 30% and an ICD also had better survival than patients with no ICD. The authors said the study was important because, while randomised trials of prophylactic ICDs had generally included patients with a LVEF of less than 30%, in practice a large number of these devices were implanted in patients with an LVEF between 30% and 35%. The retrospective cohort study included 3120 patients with an LVEF between 30% and 35% who received an ICD during a heart failure hospitalisation, with 816 matched cohorts, and 4578 with an LVEF less than 30% (2176 matched cohorts). The researchers found the risk of all-cause mortality in patients with an LVEF between 30% and 35% and an ICD was significantly lower than that in matched patients without an ICD (3-year mortality rates: 51.4% v 55.0%; hazard ratio, 0.83 [95% CI, 0.69–0.99]; P = 0.04). “Although the difference in absolute risk by 3 years was not large (3.6% at 3 years), it was significant”, they wrote. In patients with an LVEF less than 30%, the 3-year mortality rates were 45.0% v 57.6%; 634 and 660 total deaths (hazard ratio, 0.72 [95% CI, 0.65–0.81]; P < 0.001). “These findings support guideline recommendations to implant prophylactic ICDs in eligible patients with an LVEF of 35% or less”, the researchers wrote.

Dangers in DEET restrictions
RESEARCHERS have warned that restricting the N,N-diethyl-m-toluamide (DEET) concentration in insect repellents to 15% or less could increase the risk of fatal and debilitating diseases including malaria, dengue fever and yellow fever. In an article published in Parasites & Vectors, the researchers examined methods used in animal testing, observational trials and intervention studies, and information available to determine the safety of DEET in humans. “Animal testing, observational studies and intervention trials have found no evidence of severe adverse events associated with recommended DEET use”, they wrote. “The theoretical risks associated with wearing an insect repellent should be weighed against the reduction or prevention of the risk of fatal or debilitating diseases including malaria, dengue, yellow fever and filariasis.” The researchers wrote that restricting the concentration of DEET in repellents could mean inadequate personal protection for future travellers to regions where vector-borne diseases were a threat, potentially increasing the risk of disease. “DEET is the most effective and widely used insect repellent with an estimated 200 million annual applications worldwide”, they wrote. “Conventional risk assessment methodology leads to a recommendation to reduce the use of higher concentrations of DEET, but fails to recognise the disease avoiding benefits of DEET. A pragmatic approach along with future research to describe toxicity thresholds in humans are the way forward.”

Warning on recurrent Stevens-Johnson syndrome
RESEARCHERS have warned of the potentially high risks of recurrence of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) induced by drug therapy. In a research letter published in JAMA, the researchers said the risk was particularly true for drugs most commonly associated with the development of the frequently fatal conditions. They conducted a 10-year population-based cohort study in Canada based on all hospitalised Ontario residents (> 13 million). They found 567 patients hospitalised with a first episode of SJS and 141 with a first episode of TEN. The patients included 127 children younger than 18 years. Overall, 187 patients (26%) were admitted to critical care or burn units and 127 (17.9%) died in hospital (n = 84) or within 60 days of hospital discharge (n = 43), representing a short-term mortality rate of 23.4% for patients with TEN and 9.0% for SJS. They found 42 patients (7.2%) were hospitalised for a subsequent episode of SJS or TEN — equivalent to an incidence rate of 16 recurrent SJS or TEN episodes per 1000 person-years. Eight patients (1.4%) experienced multiple recurrences. “In light of the reported incidence of SJS and TEN in the general population (1.0–7.2 cases/1 million individuals/year), the observed recurrence risk in our study (> 7%) is several thousand-fold higher than would be expected if subsequent episodes were probabilistically independent of the first SJS or TEN episode”, the researchers wrote. Genetic predisposition had been identified for several medications in association with specific genotypes, such as carbamazepine-induced SJS, and recurrence had also been reported after exposure to structurally dissimilar drugs, such as carbamazepine and zonisamide, they wrote.

Divorce raises obesity risk
CHILDREN of divorced parents have an increased prevalence of general overweight and obesity, and abdominal obesity compared with children of married parents, according to research published in BMJ Open. The research included 3166 children with a mean age of 8.3 years participating in the Norwegian Child Growth Study in 2010. The researchers found children of divorced parents had a 54% higher prevalence of general overweight (including obesity) and 89% higher prevalence of abdominal obesity compared with children of married parents. Children of never-married parents had a similar prevalence to children of married parents. Boys with divorced parents seemed to be particularly affected, with 63% having a higher prevalence of general overweight (including obesity) compared to boys of married parents, with the prevalence of abdominal obesity 104% higher. The same pattern was seen for girls, but the associations were less pronounced and not statistically significant. “One can speculate as to whether the changing structure of daily life has a large effect on the children of divorced parents (living with only one parent or spending half their time with the mother and/or the father)”, the researchers wrote.

Dry eye dangers from prolonged computer use
A SMALL Japanese study of young and middle-aged office workers has found that prolonged periods of computer use and frequency of eye strain increases the risk of dry eye disease (DED). The study, published in JAMA Ophthalmology, investigated the correlation between the duration of visual display terminal (VDT) work, the presence of symptoms and signs of DED, and the concentration of mucin 5AC (MUC5AC) in office workers. The 96 workers (60 men and 36 women, aged 22–62 years) underwent tear and impression cytology sampling. Mean duration of VDT use was 8.2 hours per day for all participants, with 7.7 hours for men and 9.0 hours for women. The proportion of women with DED (13.9%) was two times greater than men (6.7%), with probable DED prevalence 53.3% in men and 63.9% in women. The researchers wrote that previous data had indicated that a decrease in the MUC5AC concentration in tears might be one of the reasons why VDT users develop DED. In their study they found a decrease in MUC5AC concentration in the tears of the definite DED group compared with the tears of the no DED group. There was also a correlation between low MUC5AC concentration and prolonged VDT working hours. “Dry eye disease is an important public health problem that causes ocular discomfort, fatigue, and visual disturbances that may interfere with daily activities”, the researchers wrote. They said their findings “suggest that the MUC5AC concentration in tears might contribute to the stability of the human tear film and the low MUC5AC concentration in tears may increase stress and induce ocular discomfort”.

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