The effect of helmets on the risk of head and neck injuries among skiers and snowboarders: a meta-analysis

Background

The prevention of head injuries in alpine activities has focused on helmets. However, no systematic review has examined the effect of helmets on head and neck injuries among skiers and snowboarders.

Methods

We searched electronic databases, conference proceedings and reference lists using a combination of the key words “head injury or head trauma,” “helmet” and “skiing or snowboarding.” We included studies that used a control group; compared skiers or snowboarders with and without helmets; and measured at least one objectively quantified outcome (e.g., head injury, and neck or cervical injury).

Results

We included 10 case–control, 1 case–control/case-crossover and 1 cohort study in our analysis. The pooled odds ratio (OR) indicated that skiers and snowboarders with a helmet were significantly less likely than those without a helmet to have a head injury (OR 0.65, 95% confidence interval [CI] 0.55–0.79). The result was similar for studies that used controls without an injury (OR 0.61, 95% CI 0.36–0.92), those that used controls with an injury other than a head or neck injury (OR 0.63, 95% CI 0.52–0.80) and studies that included children under the age of 13 years (OR 0.41, 95% CI 0.27–0.59). Helmets were not associated with an increased risk of neck injury (OR 0.89, 95% CI 0.72–1.09).

Interpretation

Our findings show that helmets reduce the risk of head injury among skiers and snowboarders with no evidence of an increased risk of neck injury.Skiing and snowboarding are popular winter activities.¹ Estimates from numerous countries indicate that head injuries account for 9% to 19%, and neck injuries for 1% to 4%, of all injuries reported by ski patrols and emergency departments.^2–11 Rates of head and neck injuries have been reported between 0.09 and 0.46 per 1000 outings.¹² Head and neck injuries are disproportionately represented in cases of severe trauma, and traumatic brain injury is the leading cause of death and serious injury among skiers and snow-boarders.¹³ As far back as 1983, Oh and Schmid recommended mandatory helmet use for children while skiing.¹⁴Many studies of the relation between helmet use and head injuries among skiers and snowboarders have found a protective effect.^15–24 It has been suggested that the use of helmets may increase the risk of neck injury in a crash or fall.²⁵ This may be more evident among children because they have a greater head:body ratio than adults, and the additional size and weight of the helmet may increase the risk of neck injury in an otherwise routine fall.²⁶ We conducted a systematic review of the effect of helmets on head and neck injuries among skiers and snowboarders.     

Effectiveness of bicycle helmets in preventing head injury in children: case-control study.

OBJECTIVE--To examine the risk of injury to the head and the effect of wearing helmets in bicycle accidents among children. DESIGN--Case-control study by questionnaire completed by the children and their carers. SETTING--Two large children''s hospitals in Brisbane, Australia. SUBJECT--445 children presenting with bicycle related injuries during 15 April 1991 to 30 June 1992. The cases comprised 102 children who had sustained injury to the upper head including the skull, forehead and scalp or loss of consciousness. The controls were 278 cyclists presenting with injuries other than to the head or face. A further 65 children with injuries to the face were considered as an extra comparison group. MAIN OUTCOME MEASURES--Cause and type of injury, wearing of helmet. RESULTS--Most children (230) were injured after losing control and falling from their bicycle. Only 31 had contact with another moving vehicle. Children with head injury were significantly more likely to have made contact with a moving vehicle than control children (19 (19%) v 12 (4%), P < 0.001). Head injuries were more likely to occur on paved surfaces than on grass, gravel, or dirt. Wearing a helmet reduced the risk of head injury by 63% (95% confidence interval 34% to 80%) and of loss of consciousness by 86% (62% to 95%). CONCLUSIONS--The risk of head injury in bicycle accidents is reduced among children wearing a helmet. Current helmet design maximises protection in the type of accident most commonly occurring in this study. Legislation enforcing helmet use among children should be considered.     

Migraine and stroke in young women: case-control study

ObjectiveTo investigate the association between migraine and ischaemic or haemorrhagic stroke in young women.DesignHospital based case-control study.SettingFive European centres participating in the World Health Organisation Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception.Subjects291 women aged 20-44 years with ischaemic, haemorrhagic, or unclassified arterial stroke compared with 736 age and hospital matched controls.InterventionQuestionnaire.ResultsAdjusted odds ratios associated with a personal history of migraine were 1.78 (95% confidence intervals, 1.14 to 2.77), 3.54 (1.30 to 9.61), and 1.10 (0.63 to 1.94) for all stroke, ischaemic stroke, and haemorrhagic stroke respectively. Odds ratios for ischaemic stroke were similar for classical migraine (with aura) (3.81, 1.26 to 11.5) and simple migraine (without aura) (2.97, 0.66 to 13.5). A family history of migraine, irrespective of personal history, was also associated with increased odds ratios, not only for ischaemic stroke but also haemorrhagic stroke. In migrainous women, coexistent use of oral contraceptives or a history of high blood pressure or smoking had greater than multiplicative effects on the odds ratios for ischaemic stroke associated with migraine alone. Change in the frequency or type of migraine on using oral contraceptives did not predict subsequent stroke. Between 20% and 40% of strokes in women with migraine seemed to develop directly from a migraine attack.ConclusionsMigraine in women of childbearing age significantly increases the risk of ischaemic but not haemorrhagic stroke. The coexistence of oral contraceptive use, high blood pressure, or smoking seems to exert a greater than multiplicative effect on the risk of ischaemic stroke associated with migraine.

Key messages

• A personal history of migraine was associated with increased risk of ischaemic but not haemorrhagic stroke
• Coexistence of risk factors—use of oral contraceptives, high blood pressure, or smoking had more than multiplicative effects on odds ratios for ischaemic stroke associated with migraine alone
• A family history of migraine, irrespective of a personal migraine history, was associated with increased risk of ischaemic and haemorrhagic stroke
• Up to 40% of strokes in migrainous women develop directly out of a migraine attack—so called migrainous strokes
• A change in type or frequency of migraine with use of oral contraceptives did not predict subsequent stroke

     

Aerodynamic study of time-trial helmets in cycling racing using CFD analysis

The aerodynamic drag of three different time-trial cycling helmets was analyzed numerically for two different cyclist head positions. Computational Fluid Dynamics (CFD) methods were used to investigate the detailed airflow patterns around the cyclist for a constant velocity of 15 m/s without wind. The CFD simulations have focused on the aerodynamic drag effects in terms of wall shear stress maps and pressure coefficient distributions on the cyclist/helmet system. For a given head position, the helmet shape, by itself, obtained a weak effect on a cyclist’s aerodynamic performance (<1.5%). However, by varying head position, a cyclist significantly influences aerodynamic performance; the maximum difference between both positions being about 6.4%. CFD results have also shown that both helmet shape and head position significantly influence drag forces, pressure and wall shear stress distributions on the whole cyclist’s body due to the change in the near-wake behavior and in location of corresponding separation and attachment areas around the cyclist.     

Anticonvulsant use and fracture: a case-control study

Objectives:We aimed to investigate fracture risk associated with anticonvulsant use in a population-based sample of men and women.Methods:Data from 1,458 participants (51.8% women) with a radiologically confirmed incident fracture (cases) were compared to 1,796 participants (46.5% women) without fracture (controls). Lifestyle factors, medication use and medical history were self-reported. Associations between anticonvulsant use and fracture were explored using binary logistic regression following adjustment for confounders.Results:In men, fracture cases and controls differed in age, smoking history, education, alcohol use, and gonadal hormone supplementation. In women, fracture cases and controls differed by previous fracture history, alcohol use, physical activity levels and use of anti-fracture agents. After adjustment for age, pooled anticonvulsant use was associated with a 3.4-fold higher risk of fracture in men and a 1.8-fold higher risk in women. Following further adjustments for confounders these patterns persisted; a 2.8-fold higher fracture risk in men and a 1.8-fold higher fracture risk in women.Conclusions:Anticonvulsant use was associated with increased fracture risk, independent of demographic, lifestyle, medical and medication related factors. While further studies exploring potential underlying mechanisms are warranted, regular monitoring of bone health in anticonvulsant users with risk factors may be useful.     

Benzodiazepines and hip fractures in elderly people: case-control study

ObjectiveTo determine whether benzodiazepines are associated with an increased risk of hip fracture.DesignCase-control study.ParticipantsAll incident cases of hip fracture not related to traffic accidents or cancer in patients over 65 years of age. 245 cases were matched to 817 controls.SettingEmergency department of a university hospital.ResultsThe use of benzodiazepines as determined from questionnaires, medical records, or plasma samples at admission to hospital was not associated with an increased risk of hip fracture (odds ratio 0.9, 95% confidence interval 0.5 to 1.5). Hip fracture was, however, associated with the use of two or more benzodiazepines, as determined from questionnaires or medical records but not from plasma samples. Of the individual drugs, only lorazepam was significantly associated with an increased risk of hip fracture (1.8, 1.1 to 3.1).ConclusionExcept for lorazepam, the presence of benzodiazepines in plasma was not associated with an increased risk of hip fracture. The method used to ascertain exposure could influence the results of case-control studies.

What is already known on this topic

Benzodiazepines increase the risk of elderly people falling in a dose dependent wayTheir role in hip fracture remains disputed, with increased risk sometimes attributed to drugs with a longer half life or those used to induce sleep

What this study adds

Benzodiazepines were not associated with hip fracture either as a group or according to half life or to characterisation as hypnotic or anxiolyticPatients using two or more benzodiazepines may be at higher riskPatients using lorazepam or certain other benzodiazepines may also be at a higher risk of fracture     

Incidence and predictors of severe obstetric morbidity: case-control study

ObjectiveTo estimate the incidence and predictors of severe obstetric morbidity.DesignDevelopment of definitions of severe obstetric morbidity by literature review. Case-control study from a defined delivery population with four randomly selected pregnant women as controls for every case.SettingAll 19 maternity units within the South East Thames region and six neighbouring hospitals caring for pregnant women from the region between 1 March 1997 and 28 February 1998.Participants48 865 women who delivered during the time frame.ResultsThere were 588 cases of severe obstetric morbidity giving an incidence of 12.0/1000 deliveries (95% confidence interval 11.2 to 13.2). During the study there were five maternal deaths attributed to conditions studied. Disease specific morbidities per 1000 deliveries were 6.7 (6.0 to 7.5) for severe haemorrhage, 3.9 (3.3 to 4.5) for severe pre-eclampsia, 0.2 (0.1 to 0.4) for eclampsia, 0.5 (0.3 to 0.8) for HELLP (Haemolysis, Elevated Liver enzymes, and Low Platelets) syndrome, 0.4 (0.2 to 0.6) for severe sepsis, and 0.2 (0.1 to 0.4) for uterine rupture. Age over 34 years, non-white ethnic group, past or current hypertension, previous postpartum haemorrhage, delivery by emergency caesarean section, antenatal admission to hospital, multiple pregnancy, social exclusion, and taking iron or anti-depressants at antenatal booking were all independently associated with morbidity after adjustment.ConclusionSevere obstetric morbidity and its relation to mortality may be more sensitive measures of pregnancy outcome than mortality alone. Most events are related to obstetric haemorrhage and severe pre-eclampsia. Caesarean section quadruples the risk of morbidity. Development and evaluation of ways of predicting and reducing risk are required with particular emphasis paid on the management of haemorrhage and pre-eclampsia.

What is already known on this topic

Maternal mortality is used internationally as a measure of the quality of obstetric intervention, although it is now rare in the developed worldHospital based series estimating the incidence of severe obstetric morbidity have used different definitionsEstimated incidence of severe obstetric morbidity ranges from 0.05 to 1.09

What this study adds

With clear definitions and population based estimates of some severe obstetric morbidities this study estimated the overall incidence of severe obstetric morbidity as 1.2 % of deliveriesTwo thirds of the cases are related to severe haemorrhage, one third to hypertensive disordersRisk factors for severe maternal morbidity include maternal age >34, social exclusion, non-white, hypertension, previous postpartum haemorrhage, induction of labour, and caesarean section     

Risk of testicular cancer in subfertile men: case-control study

ObjectiveTo evaluate the association between subfertility in men and the subsequent risk of testicular cancer.DesignPopulation based case-control study.SettingThe Danish population.ParticipantsCases were identified in the Danish Cancer Registry; controls were randomly selected from the Danish population with the computerised Danish Central Population Register. Men were interviewed by telephone; 514 men with cancer and 720 controls participated.ResultsA reduced risk of testicular cancer was associated with paternity (relative risk 0.63; 95% confidence interval 0.47 to 0.85). In men who before the diagnosis of testicular cancer had a lower number of children than expected on the basis of their age, the relative risk was 1.98 (1.43 to 2.75). There was no corresponding protective effect associated with a higher number of children than expected. The associations were similar for seminoma and non-seminoma and were not influenced by adjustment for potential confounding factors.ConclusionThese data are consistent with the hypothesis that male subfertility and testicular cancer share important aetiological factors.

Key messages

• The incidence of testicular cancer has increased in the past 50 years, and there is some evidence to suggest that sperm quality has decreased in the same period
• It has been hypothesised that common aetiological factors may exist for testicular cancer and for male subfertility
• The association between male subfertility and subsequent risk of testicular cancer is strong and consistent with the hypothesis of a common aetiology
• The association is similar for seminoma and non-seminoma, and it persists when several potentially confounding factors are taken into account

     

Psoriasis and hypertension severity: results from a case-control study

Background

Epidemiologic studies have provided new insights into the association between psoriasis and cardiovascular diseases. Previous population studies have examined hypertension frequency in psoriasis patients. However, the relationship between severity of hypertension and psoriasis has not been characterized.

Objective

We sought to investigate whether patients with psoriasis have more difficult-to-manage hypertension compared to non-psoriatic hypertensive patients.

Approach

We performed a case-control study using the University of California Davis electronic medical records. The cases were defined as patients diagnosed with both psoriasis and hypertension, and controls were defined as patients with hypertension and without psoriasis. In this identified population, 835 cases were matched on age, sex, and body mass index (BMI) to 2418 control patients.

Key Results

Treatment with multiple anti-hypertensives was significantly associated with the presence of psoriasis using univariate (p<0.0001) and multivariable analysis, after adjusting for diabetes, hyperlipidemia, and race (p<0.0001). Compared to hypertensive patients without psoriasis, psoriasis patients with hypertension were 5 times more likely to be on a monotherapy antihypertensive regimen (95% CI 3.607.05), 9.5 times more likely to be on dual antihypertensive therapy (95% CI 6.68–13.65), 16.5 times more likely to be on triple antihypertensive regimen (95% CI 11.01–24.84), and 19.9 times more likely to be on quadruple therapy or centrally-acting agent (95% CI 10.58–37.33) in multivariable analysis after adjusting for traditional cardiac risk factors.

Conclusions

Psoriasis patients appear to have more difficult-to-control hypertension compared to non-psoriatic, hypertensive patients.     

Adverse life events and breast cancer: case-control study.

OBJECTIVE--To investigate the strength of association between past life events and the development of breast cancer. DESIGN--Case-control study. A standardised life events interview and rating was administered before a definitive diagnosis. SETTING--Breast Cancer Screening Assessment Unit and surgical outpatient clinics at King''s College Hospital, London. SUBJECTS--119 consecutive women aged 20-70 who were referred for biopsy of a suspicious breast lesion. MAIN OUTCOME MEASURES--Odds ratio of the risk of developing breast cancer after life events in the preceding five years after adjustment for confounders. RESULTS--41 women were diagnosed as having malignant disease while the remainder had benign conditions. Severe life events increased the risk of breast cancer. The crude odds ratio was 3.2 (95% confidence interval 1.35 to 7.6). After adjustment for age and the menopause and other potential confounders this rose to 11.6 (3.1 to 43.7). Multiple logistic regression analysis showed that all severe events and coping with the stress of adverse events by confronting them and focusing on the problems significantly predicted a diagnosis of breast cancer. Non-severe life events and long term difficulties had no significant association. CONCLUSION--These findings suggest an aetiological association between life stress and breast cancer.     

Plasma fatty acid profiles in autism: A case-control study

Increasing evidence is mounting in support of fatty acid metabolism playing a role in neurodevelopmental disorders such as autism. In order to definitely determine whether fatty acid concentrations were associated with autism, we quantitatively measured 30 fatty acids from seven lipid classes in plasma from a large subset of subjects enrolled in the Childhood Autism Risk from Genetics and the Environment (CHARGE) study. The CHARGE study is a large, population-based case-control study on children aged 2–5 born in California. Our subset consisted of 153 children with autism and 97 developmentally normal controls. Results showed that docosahexaenoic acid (DHA, 22:6n-3) was significantly decreased in phosphatidylethanolamine. Dimethyl acetals were significantly decreased in phosphatidylethanolamine and phosphatidylcholine as well. These results are consistent with the only other study to measure dimethyl acetals in children with autism, and suggest that the function of peroxisomes and the enzymes of the peroxisome involved with fatty acid metabolism may be affected in autism.     

Migraine and risk of ischaemic stroke: a case-control study.

OBJECTIVES--To determine whether migraine is a risk factor for ischaemic stroke. DESIGN--A case-control study. SETTING--Two hospitals in Paris. SUBJECTS--212 patients with stroke (137 men and 75 women) and 212 controls matched for sex, age (to within five years), and history of hypertension. MAIN OUTCOME MEASURES--Ischaemic stroke, confirmed by brain computed tomography or magnetic resonance imaging, and history of headache, recorded with structured questionnaire during interview. RESULTS--Prevalence of migraine did not differ between patients with stroke and controls: 18/137 v 17/137 for men (odds ratio 1.1 (95% confidence interval 0.5 to 2.2), p = 0.86); 23/75 v 17/75 for women (odds ratio 1.6 (0.7 to 3.5), p = 0.24); and 41/212 v 34/212 for both sexes (odds ratio 1.3 (0.8 to 2.3), p = 0.33). When subjects were split into two age groups, however, prevalence of migraine was significantly higher among younger women (aged < 45) with stroke compared with their controls (13/20 v 6/20, odds ratio 4.3 (1.2 to 16.3), p = 0.03). Furthermore, the risk of ischaemic stroke was higher among younger women who smoked (7/20 v 1/20, odds ratio 10.2 (1.1 to 93.3)). CONCLUSIONS--Prevalence of migraine was not different between patients with stroke and matched controls except among women aged < 45, when migraine and stroke were significantly associated.