Daniel Mackay

Smoke-free Legislation and Hospitalizations for Childhood Asthma

BACKGROUND Previous studies have shown that after the adoption of comprehensive smoke-free legislation, there is a reduction in respiratory symptoms among workers in bars. However, it is not known whether respiratory disease is also reduced among people who do not have occupational exposure to environmental tobacco smoke. The aim of our study was to determine whether the ban on smoking in public places in Scotland, which was initiated in March 2006, influenced the rate of hospital admissions for childhood asthma. METHODS Routine hospital administrative data were used to identify all hospital admissions for asthma in Scotland from January 2000 through October 2009 among children younger than 15 years of age. A negative binomial regression model was fitted, with adjustment for age group, sex, quintile of socioeconomic status, urban or rural residence, month, and year. Tests for interactions were also performed. RESULTS Before the legislation was implemented, admissions for asthma were increasing at a mean rate of 5.2% per year (95% confidence interval [CI], 3.9 to 6.6). After implementation of the legislation, there was a mean reduction in the rate of admissions of 18.2% per year relative to the rate on March 26, 2006 (95% CI, 14.7 to 21.8; P<0.001). The reduction was apparent among both preschool and school-age children. There were no significant interactions between hospital admissions for asthma and age group, sex, urban or rural residence, region, or quintile of socioeconomic status. CONCLUSIONS In Scotland, passage of smoke-free legislation in 2006 was associated with a subsequent reduction in the rate of respiratory disease in populations other than those with occupational exposure to environmental tobacco smoke. (Funded by NHS Health Scotland.)

Gestational Age at Delivery and Special Educational Need: Retrospective Cohort Study of 407,503 Schoolchildren

A retrospective cohort study of 407,503 schoolchildren by Jill Pell and colleagues finds that gestational age at delivery has a dose-dependent relationship with the risk of special educational needs that extends across the full gestational range.

Systematic review and meta-analysis of school-based interventions to reduce body mass index

BACKGROUND Childhood obesity predisposes to adult obesity and increases the risk of many diseases. Schools provide a vehicle to deliver public health interventions to all children. METHODS Medline and Embase were used to undertake a systematic review of published studies of school-based interventions aimed at reducing the body mass index (BMI) of children ≤ 18 years. Preferred reporting items for systematic reviews and meta-analyses guidelines were followed, and eligible studies subjected to a random effects meta-analysis. RESULTS Between 1991 and 2010, 43 published studies provided 60 measurements of effect. The pooled effect was a 0.17 (95% CI: 0.08, 0.26, P < 0.001) reduction in BMI. Heterogeneity was high (I(2) = 93.4%) but there was no significant small study bias (Eggers test, P = 0.422) nor significant variation by length of follow-up. The intervention comprised physical activity only in 11 (26%) studies, education only in three (7%), and combinations of these and improved nutrition in the remaining 29 (67%). On stratified analysis, physical activity used in isolation (-0.13, 95% CI: -0.22, -0.04, P = 0.001) or combined with improved nutrition (-0.17, 95% CI: -0.29, -0.06, P < 0.001) was associated with significant improvements in BMI. Interventions targeted at overweight/obese children reduced their BMI by 0.35 (95% CI: 0.12, 0.58, P = 0.003). Those delivered to all children reduced it by 0.16 (95% CI: 0.06, 0.25, P = 0.002). CONCLUSIONS There is growing evidence that school-based interventions that contain a physical activity component may be effective in helping to reduce BMI in children.

Meta-analysis of the effect of comprehensive smoke-free legislation on acute coronary events

Objective To assess the evidence for a reduced risk of acute coronary events following comprehensive smoke-free legislation. Methods Two independent systematic reviews were undertaken using PubMed, Embase and Science Direct with no date restrictions imposed. Meta-analysis was undertaken using a random effects model to obtain a pooled estimate of the relative risk. Linear regression was used to examine possible bias and meta-regression was used to investigate possible causes of heterogeneity. Main outcome measure Acute coronary events. Results The 17 eligible studies (10 from North America, 6 from Europe and 1 from Australasia) provided 35 estimates of effect size. Apart from five subgroup analyses, all of the published results suggested a reduction in the incidence of acute coronary events following the introduction of smoke-free legislation. Meta-analysis produced a pooled estimate of the relative risk of 0.90 (95% CI 0.86 to 0.94). There was significant heterogeneity (overall I2=95.1%, p<0.001) but there was no evidence of small study bias (p=0.714). On univariate random effects meta-regression analysis, studies with longer data collection following legislation produced greater estimates of risk reduction and remained significant after adjustment for other study characteristics (adjusted coefficient −0.005, 95% CI −0.007 to −0.002, multiplicity adjusted p=0.006). Conclusions There is now a large body of evidence supporting a reduction in acute coronary events following the implementation of comprehensive smoke-free legislation, with the effect increasing over time from implementation. Countries that have not yet adopted smoke-free legislation should be encouraged to do so.

Meta‐analysis of the association between body mass index and health‐related quality of life among adults, assessed by the SF‐36

Obesity is associated with impaired overall health‐related quality of life but individual studies suggest the relationship may differ for mental and physical quality of life. A systematic review using Medline, Embase, PsycINFO and ISI Web of Knowledge, and random effects meta‐analysis was undertaken.

Ethnic-Specific Obesity Cutoffs for Diabetes Risk: Cross-sectional Study of 490,288 UK Biobank Participants

OBJECTIVE To compare the relationship between adiposity and prevalent diabetes across ethnic groups in the UK Biobank cohort and to derive ethnic-specific obesity cutoffs that equate to those developed in white populations in terms of diabetes prevalence. RESEARCH DESIGN AND METHODS UK Biobank recruited 502,682 U.K. residents aged 40–69 years. We used baseline data on the 490,288 participants from the four largest ethnic subgroups: 471,174 (96.1%) white, 9,631 (2.0%) South Asian, 7,949 (1.6%) black, and 1,534 (0.3%) Chinese. Regression models were developed for the association between anthropometric measures (BMI, waist circumference, percentage body fat, and waist-to-hip ratio) and prevalent diabetes, stratified by sex and adjusted for age, physical activity, socioeconomic status, and heart disease. RESULTS Nonwhite participants were two- to fourfold more likely to have diabetes. For the equivalent prevalence of diabetes at 30 kg/m2 in white participants, BMI equated to the following: South Asians, 22.0 kg/m2; black, 26.0 kg/m2; Chinese women, 24.0 kg/m2; and Chinese men, 26.0 kg/m2. Among women, a waist circumference of 88 cm in the white subgroup equated to the following: South Asians, 70 cm; black, 79 cm; and Chinese, 74 cm. Among men, a waist circumference of 102 cm equated to 79, 88, and 88 cm for South Asian, black, and Chinese participants, respectively. CONCLUSIONS Obesity should be defined at lower thresholds in nonwhite populations to ensure that interventions are targeted equitably based on equivalent diabetes prevalence. Furthermore, within the Asian population, a substantially lower obesity threshold should be applied to South Asian compared with Chinese groups.

Meta-analysis of the association between preterm delivery and intelligence

BACKGROUND An increasing proportion of infants are born preterm, and their survival has improved. Therefore, their long-term sequelae are of increasing public health importance. METHODS We conducted a systematic review covering a 30 year period (1980-2009). A random effects meta-analysis provided a pooled estimate of the difference in IQ score between individuals born preterm and term. Small-study bias was examined using a funnel plot and Eggers test, and meta-regression was used to investigate possible causes of heterogeneity. Cumulative meta-analysis was used to determine if the magnitude of the association had changed over time. RESULTS The 27 eligible studies covered 7044 individuals; 3504 (50%) delivered preterm and 3540 (50%) at term. They provided 37 estimates of difference in IQ. All demonstrated a reduced IQ among those delivered preterm and all but four reached statistical significance. Overall, IQ score was 11.94 (95% CI: 10.47-13.42, P < 0.001) points lower among children born preterm. There was moderate heterogeneity (overall I(2) 74.2%, P < 0.001), but no significant small-study bias (P = 0.524). The association between preterm delivery and IQ did not change significantly over time. There was a statistically significant, linear association across the gestational age range (adjusted coefficient: -0.91, 95% CI: -1.64, -0.17, P = 0.018). CONCLUSIONS There is a strong and consistent body of evidence suggesting an association between preterm delivery and reduced IQ, with evidence of a dose-response relationship with gestational age.

Prevalence and Characteristics of Probable Major Depression and Bipolar Disorder within UK Biobank: Cross-Sectional Study of 172,751 Participants

Objectives UK Biobank is a landmark cohort of over 500,000 participants which will be used to investigate genetic and non-genetic risk factors for a wide range of adverse health outcomes. This is the first study to systematically assess the prevalence and validity of proposed criteria for probable mood disorders within the cohort (major depression and bipolar disorder). Methods This was a descriptive epidemiological study of 172,751 individuals assessed for a lifetime history of mood disorder in relation to a range of demographic, social, lifestyle, personality and health-related factors. The main outcomes were prevalence of a probable lifetime (single) episode of major depression, probable recurrent major depressive disorder (moderate), probable recurrent major depressive disorder (severe), probable bipolar disorder and no history of mood disorder (comparison group). Outcomes were compared on age, gender, ethnicity, socioeconomic status, educational attainment, functioning, self-reported health status, current depressive symptoms, neuroticism score, smoking status and alcohol use. Results Prevalence rates for probable single lifetime episode of major depression (6.4%), probable recurrent major depression (moderate) (12.2%), probable recurrent major depression (severe) (7.2%) and probable bipolar disorder (1.3%) were comparable to those found in other population studies. The proposed diagnostic criteria have promising validity, with a gradient in evidence from no mood disorder through major depression and probable bipolar disorder in terms of gender distribution, socioeconomic status, self-reported health rating, current depressive symptoms and smoking. Significance The validity of our proposed criteria for probable major depression and probable bipolar disorder within this cohort are supported by these cross-sectional analyses. Our findings are likely to prove useful as a framework for a wide range of future genetic and non-genetic studies.

Apgar score and the risk of cause-specific infant mortality: a population-based cohort study

BACKGROUND The Apgar score has been used worldwide as an index of early neonatal condition for more than 60 years. With advances in health-care service provision, neonatal resuscitation, and infant care, its present relevance is unclear. The aim of the study was to establish the strength of the relation between Apgar score at 5 min and the risk of neonatal and infant mortality, subdivided by specific causes. METHODS We linked routine discharge and mortality data for all births in Scotland, UK between 1992 and 2010. We restricted our analyses to singleton livebirths, in women aged over 10 years, with a gestational age at delivery between 22 and 44 weeks, and excluded deaths due to congenital anomalies or isoimmunisation. We calculated the relative risks (RRs) of neonatal and infant death of neonates with low (0-3) and intermediate (4-6) Apgar scores at 5 min referent to neonates with normal Apgar score (7-10) using binomial log-linear modelling with adjustment for confounders. Analyses were stratified by gestational age at birth because it was a significant effect modifier. Missing covariate data were imputed. FINDINGS Complete data were available for 1,029,207 eligible livebirths. Across all gestational strata, low Apgar score at 5 min was associated with an increased risk of neonatal and infant death. However, the strength of the association (adjusted RR, 95% CI referent to Apgar 7-10) was strongest at term (p<0·0001). A low Apgar (0-3) was associated with an adjusted RR of 359·4 (95% CI 277·3-465·9) for early neonatal death, 30·5 (18·0-51·6) for late neonatal death, and 50·2 (42·8-59·0) for infant death. We noted similar associations of a lower magnitude for intermediate Apgar (4-6). The strongest associations were for deaths attributed to anoxia and low Apgar (0-3) for term infants (RR 961·7, 95% CI 681·3-1357·5) and preterm infants (141·7, 90·1-222·8). No association between Apgar score at 5 min and the risk of sudden infant death syndrome was noted at any gestational age (RR 0·6, 95% CI 0·1-4·6 at term; 1·2, 0·3-4·8 at preterm). INTERPRETATION Low Apgar score at 5 min was strongly associated with the risk of neonatal and infant death. Our findings support its continued usefulness in contemporary practice. FUNDING None.

Meta-analysis of the association between secondhand smoke exposure and stroke

BACKGROUND Active smoking is a recognized risk factor for stroke. We determined the evidence for an association with secondhand smoke exposure. METHODS A systematic review was undertaken according to PRISMA guidelines. Random effects meta-analysis provided a pooled estimate of risk, and heterogeneity quantified using I(2) values. Potential publication and study bias were assessed using a funnel plot and Eggers test. Meta-regression analyses were used to investigate sources of heterogeneity. RESULTS The 20 eligible studies provided 35 estimates of risk derived from 885 307 participants, of whom 5894 (0.7%) suffered a stroke. The pooled estimate of risk was 1.25 (95% CI: 1.12-1.38) with no evidence of significant publication or small-study bias. There was moderate heterogeneity (I(2) = 54.2%, P < 0.001) but no study characteristics were statistically significant in the meta-regression analysis. There was a non-linear dose relationship. The relative risk increased from 1.16 (95% CI: 1.06-1.27) for exposure to 5 cigarettes/day to 1.56 (95% CI: 1.25-1.96) for exposure to 40 cigarettes/day. CONCLUSIONS There is evidence of a strong, consistent and dose-dependent association between exposure to secondhand smoke and risk of stroke, suggestive of a causal relationship, with disproportionately high risk at low levels of exposure suggesting no safe lower limit of exposure.