Introduction The use of movement monitors (accelerometers) for measuring physical activity (PA) in intervention and population-based studies is becoming a standard methodology for the objective measurement of sedentary and active behaviors and for validation of subjective PA self-reports. A vital step in PA measurements is classification of daily time into accelerometer wear and nonwear intervals using its recordings (counts) and an accelerometer-specific algorithm. Purpose To validate and improve a commonly used algorithm for classifying accelerometer wear and nonwear time intervals using objective movement data obtained in the whole-room indirect calorimeter. Methods We conducted a validation study of a wear/nonwear automatic algorithm using data obtained from 49 adults and 76 youth wearing accelerometers during a strictly monitored 24-h stay in a room calorimeter. The accelerometer wear and nonwear time classified by the algorithm was compared with actual wearing time. Potential improvements to the algorithm were examined using the minimum classification error as an optimization target. Results The recommended elements in the new algorithm are: 1) zero-count threshold during a nonwear time interval, 2) 90-min time window for consecutive zero/nonzero counts, and 3) allowance of 2-min interval of nonzero counts with the up/downstream 30-min consecutive zero counts window for detection of artifactual movements. Compared to the true wearing status, improvements to the algorithm decreased nonwear time misclassification during the waking and the 24-h periods (all P < 0.001). Conclusions The accelerometer wear/nonwear time algorithm improvements may lead to more accurate estimation of time spent in sedentary and active behaviors.

Background Prospective data on viral etiology and clinical characteristics of bronchiolitis and upper respiratory illness in infants is limited. Methods This prospective cohort enrolled previously healthy term infants during inpatient or outpatient visits for acute upper respiratory illness (URI) or bronchiolitis during September - May 2004–2008. Illness severity was determined using an ordinal bronchiolitis severity score. Common respiratory viruses were identified by real-time RT-PCR. Results Of 648 infants, 67% were enrolled during inpatient visits and 33% during outpatient visits. Seventy percent had bronchiolitis, 3% croup, and 27% URI. Among infants with bronchiolitis, 76% had RSV, 18% HRV, 10% influenza, 2% coronavirus, 3% HMPV, and 1% PIV. Among infants with croup, 39% had HRV, 28% PIV, 28% RSV, 11% influenza, 6% coronavirus, and none HMPV. Among infants with URI, 46% had HRV, 14% RSV, 12% influenza, 7% coronavirus, 6% PIV, and 4% HMPV. Individual viruses exhibited distinct seasonal, demographic, and clinical expression. Conclusions The most common infections among infants seeking care in unscheduled medical visits for URI or bronchiolitis were RSV and HRV. Demographic differences were observed between patients with different viruses, suggesting that host and viral factors play a role in phenotypic expression of viral illness.

Background-Risk factors for severe human rhinovirus (HRV) associated infant illness are unknown.

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Background Evidence establishing effectiveness of influenza vaccination for prevention of severe illness is limited. The US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) is a multiyear test-negative case-control study initiated in 2015–2016 to estimate effectiveness of vaccine in preventing influenza hospitalization among adults. Methods Adults aged ≥18 years admitted to 8 US hospitals with acute respiratory illness and testing positive for influenza by polymerase chain reaction were cases; those testing negative were controls. Vaccine effectiveness was estimated with logistic regression adjusting for age, comorbidities, and other confounding factors and stratified by frailty, 2-year vaccination history, and clinical presentation. Results We analyzed data from 236 cases and 1231 controls; mean age was 58 years. More than 90% of patients had ≥1 comorbidity elevating risk of influenza complications. Fifty percent of cases and 70% of controls were vaccinated. Vaccination was 51% (95% confidence interval [CI], 29%–65%) and 53% (95% CI, 11%–76%) effective in preventing hospitalization due to influenza A(H1N1)pdm09 and influenza B virus infection, respectively. Vaccine was protective for all age groups. Conclusions During the 2015–2016 US influenza A(H1N1)pdm09–predominant season, we found that vaccination halved the risk of influenza-association hospitalization among adults, most of whom were at increased risk of serious influenza complications due to comorbidity or age.

Background Respiratory syncytial virus (RSV) and rhinovirus infections are the most common significant infant respiratory illnesses and are associated with increased but differential risks of childhood asthma. Objective Determine whether maternal asthma is associated with higher odds of infant respiratory infection with rhinovirus versus RSV and increased infection severity. Methods Mother-infant dyads were enrolled 2004–2008 during an infant respiratory infection (104 rhinovirus, 279 RSV). Mothers were classified into mutually exclusive groups (atopic asthma, non-atopic asthma, no asthma). We determined viral etiology by polymerase chain reaction and severity of infant respiratory infection by bronchiolitis severity score. Adjusted relative odds of maternal asthma with viral etiology were calculated using logistic regression. Proportional odds models assessed the association of maternal asthma and infant infection severity. Results Infants with a mother with atopic asthma compared to infants whose mothers did not have asthma were more likely to have rhinovirus versus RSV infection (adjusted odds ratio 2.42 [95% CI: 1.19–4.90]). Similarly, among infants with rhinovirus, having a mother with atopic asthma was associated with increased infection severity (adjusted odds ratio 3.10, 95% CI 1.21–7.98). This relationship was not seen among infants with RSV. Conclusions Clinically significant rhinovirus infection during infancy was more strongly associated with having a mother with atopic asthma than clinically significant RSV infection. Having a mother with atopic asthma was associated with increased severity of infant rhinovirus, but not RSV infections. Infants with rhinovirus were more likely to have a familial atopic predisposition, which may partly explain subsequent increased asthma risk.

Objective Investigate the association of maternal vitamin D and maternal asthma and infant respiratory infection severity. Study Design Cross-sectional analyses of 340 mother-infant dyads enrolled September-May 2004-2008 during an infant viral respiratory infection. Maternal vitamin D levels were determined from enrollment blood specimens. At enrollment, we determined self-reported maternal asthma and infant respiratory infection severity using a bronchiolitis score. We assessed the association of maternal vitamin D levels and maternal asthma and infant bronchiolitis score in race-stratified multivariable regression models. Results The cohort was 70% White, 19% African-American, and 21% had asthma. Overall, the median maternal vitamin D level was 20 ng/ml (Interquartile range 14,28). Among White women, a 14 ng/ml increase in vitamin D was associated with decreased odds of asthma (AOR 0.54, 95% CI 0.33-0.86). Maternal vitamin D was not associated with infant bronchiolitis score. Conclusions Higher maternal vitamin D levels were associated with decreased odds of asthma.

In a cross-sectional analysis of 629 mother-infants dyads, breastfeeding (ever vs. never) was associated with a decreased relative odds of a lower versus upper respiratory tract infection (AOR: 0.64; 95% CI: 0.42, 0.99). There was not a significant association between breastfeeding and bronchiolitis severity score or length of hospital stay.