Lai-Ming Ho

Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong

Summary Background Health authorities worldwide, especially in the Asia Pacific region, are seeking effective public-health interventions in the continuing epidemic of severe acute respiratory syndrome (SARS). We assessed the epidemiology of SARS in Hong Kong. Methods We included 1425 cases reported up to April 28, 2003. An integrated database was constructed from several sources containing information on epidemiological, demographic, and clinical variables. We estimated the key epidemiological distributions: infection to onset, onset to admission, admission to death, and admission to discharge. We measured associations between the estimated case fatality rate and patients’age and the time from onset to admission. Findings After the initial phase of exponential growth, the rate of confirmed cases fell to less than 20 per day by April 28. Public-health interventions included encouragement to report to hospital rapidly after the onset of clinical symptoms, contact tracing for confirmed and suspected cases, and quarantining, monitoring, and restricting the travel of contacts. The mean incubation period of the disease is estimated to be 6.4 days (95% Cl 5.2–7.7). The mean time from onset of clinical symptoms to admission to hospital varied between 3 and 5 days, with longer times earlier in the epidemic. The estimated case fatality rate was 13.2% (9.8–16.8) for patients younger than 60 years and 43.3% (35.2–52.4) for patients aged 60 years or older assuming a parametric γ distribution. A non-parametric method yielded estimates of 6.8% (4.0–9.6) and 55.0% (45.3–64.7), respectively. Case clusters have played an important part in the course of the epidemic. Interpretation Patients’age was strongly associated with outcome. The time between onset of symptoms and admission to hospital did not alter outcome, but shorter intervals will be important to the wider population by restricting the infectious period before patients are placed in quarantine. Published online May 7, 2003 http://image.thelancet.com/extras/03art4453web.pdf

The infection attack rate and severity of 2009 pandemic H1N1 influenza in Hong Kong

BACKGROUND Serial cross-sectional data on antibody levels to the 2009 pandemic H1N1 influenza A virus from a population can be used to estimate the infection attack rates and immunity against future infection in the community. METHODS From April through December 2009, we obtained 12,217 serum specimens from blood donors (aged 16-59 years), 2520 specimens from hospital outpatients (aged 5-59 years), and 917 specimens from subjects involved in a community pediatric cohort study (aged 5-14 years). We estimated infection attack rates by comparing the proportions of specimens with antibody titers ≥ 1:40 by viral microneutralization before and after the first wave of the pandemic. Estimates were validated using paired serum samples from 324 individuals that spanned the first wave. Combining these estimates with epidemiologic surveillance data, we calculated the proportion of infections that led to hospitalization, admission to the intensive care unit (ICU), and death. RESULTS We found that 3.3% and 14% of persons aged 5-59 years had antibody titers ≥ 1:40 before and after the first wave, respectively. The overall attack rate was 10.7%, with age stratification as follows: 43.4% in persons aged 5-14 years, 15.8% in persons aged 15-19 years, 11.8% in persons aged 20-29 years, and 4%-4.6% in persons aged 30-59 years. Case-hospitalization rates were 0.47%-0.87% among persons aged 5-59 years. Case-ICU rates were 7.9 cases per 100,000 infections in persons aged 5-14 years and 75 cases per 100,000 infections in persons aged 50-59 years, respectively. Case-fatality rates were 0.4 cases per 100,000 infections in persons aged 5-14 years and 26.5 cases per 100,000 infections in persons aged 50-59 years, respectively. CONCLUSIONS Almost half of all school-aged children in Hong Kong were infected during the first wave. Compared with school children aged 5-14 years, older adults aged 50-59 years had 9.5 and 66 times higher risks of ICU admission and death if infected, respectively.

The development and validation of a knowledge, attitude and behaviour questionnaire to assess undergraduate evidence-based practice teaching and learning

Objectives  Most evidence‐based practice (EBP) educational assessment tools evaluated to date have focused on specific knowledge components or technical skills. Other important potential barriers to the adoption of EBP, such as attitudinal, perceptual and behavioural factors, have yet to be studied, especially in the undergraduate setting. Therefore, we developed and validated a knowledge, attitude and behaviour questionnaire designed to evaluate EBP teaching and learning in an undergraduate medical curriculum.

Birth Weight, Infant Growth, and Childhood Body Mass Index: Hong Kong's Children of 1997 Birth Cohort

OBJECTIVE To investigate the association between birth weight, infant growth rate, and childhood adiposity as a proxy for adult metabolic or cardiovascular risk in a Chinese population with a history of recent and rapid economic development. DESIGN Prospective study in a population-representative birth cohort. SETTING Hong Kong Chinese population. PARTICIPANTS Six thousand seventy-five term births (77.5% successful follow-up). Main Exposures Birth weight and growth rate (change in the weight z score) at ages 0 to 3 and 3 to 12 months. Main Outcome Measure Body mass index (BMI) (calculated as the weight in kilograms divided by the height in meters squared) z score at about age 7 years. RESULTS Each unit increase in the weight z score at ages 0 to 3 and 3 to 12 months increased the BMI z score by 0.52 and 0.33, respectively. Children in the highest birth weight and growth rate tertiles had the highest BMI z scores. In the lowest birth weight tertile, increases in the weight z score at ages 0 to 3 months had a larger effect on the BMI z score in boys (mean difference, 0.88; 95% confidence interval 0.69-1.07) than in girls (mean difference, 0.52; 95% confidence interval, 0.33-0.71); these differences by birth weight, growth rate at ages 0 to 3 months, and sex were significant (P = .007). CONCLUSIONS Faster prenatal and postnatal growth were associated with higher childhood BMI in a population with a recent history of rapid economic growth and relatively low birth weight, suggesting that maximal growth may not be optimal for metabolic risk. However, there may be a developmental trade-off between metabolic risk and other outcomes.

Epidemiological Characteristics of 2009 (H1N1) Pandemic Influenza Based on Paired Sera from a Longitudinal Community Cohort Study

Steven Riley and colleagues analyze a community cohort study from the 2009 (H1N1) influenza pandemic in Hong Kong, and found that more children than adults were infected with H1N1, but children were less likely to progress to severe disease than adults.

Breast-feeding and its relation to smoking and mode of delivery.

OBJECTIVE To examine the effects of cesarean and forceps or vacuum delivery and parental smoking habits on the initiation and duration of breast‐feeding. METHODS We conducted a prospective, population‐based birth cohort study in 1997. Data were collected on breast‐feeding history, household smoking habits, method of delivery, and other demographic, obstetric, behavioral, and potential confounding variables via a standardized self‐administered questionnaire. Multivariable logistic regression was used to examine the association between method of birth (cesarean versus forceps or vacuum delivery versus normal vaginal birth) and either not initiating breast‐feeding or doing so for less than 1 month. Among women who breast‐fed for 1 month or more, multivariable survival analysis was employed to study the relationship between method of delivery and breast‐feeding duration. We repeated these analyses to examine the link between parental smoking habits and breast‐feeding initiation and duration. RESULTS A total of 7825 mother‐infant pairs were followed up for 9 months. Cesarean delivery was a risk factor for not initiating breast‐feeding, for breast‐feeding less than 1 month, and remained a significant hazard against breast‐feeding duration. Assisted delivery with forceps or vacuum, although not associated with breast‐feeding initiation, was a significant risk against breast‐feeding duration. Conversely, current parental smoking habits only affected breast‐feeding initiation but were unrelated to breast‐feeding duration. CONCLUSION This study indicates a possible effect of forceps or vacuum delivery on breast‐feeding and of cesarean on long‐term breast‐feeding duration. The findings provide additional evidence in support of the avoidance of unnecessary obstetric interventions.

Excess Mortality Associated With Influenza A and B Virus in Hong Kong, 1998–2009

BACKGROUND Although deaths associated with laboratory-confirmed influenza virus infections are rare, the excess mortality burden of influenza estimated from statistical models may more reliably quantify the impact of influenza in a population. METHODS We applied age-specific multiple linear regression models to all-cause and cause-specific mortality rates in Hong Kong from 1998 through 2009. The differences between estimated mortality rates in the presence or absence of recorded influenza activity were used to estimate influenza-associated excess mortality. RESULTS The annual influenza-associated all-cause excess mortality rate was 11.1 (95% confidence interval [CI], 7.2-14.6) per 100,000 person-years. We estimated an average of 751 (95% CI, 488-990) excess deaths associated with influenza annually from 1998 through 2009, with 95% of the excess deaths occurring in persons aged ≥65 years. Most of the influenza-associated excess deaths were from respiratory (53%) and cardiovascular (18%) causes. Influenza A(H3N2) epidemics were associated with more excess deaths than influenza A(H1N1) or B during the study period. CONCLUSIONS Influenza was associated with a substantial number of excess deaths each year, mainly among the elderly, in Hong Kong in the past decade. The influenza-associated excess mortality rates were generally similar in Hong Kong and the United States.

Cohort Profile: ‘Children of 1997’: a Hong Kong Chinese birth cohort

The basis of this cohort, comprising over 88% of all ethnic Chinese births during April and May of 1997 in Hong Kong, is a large, prospective, populationrepresentative study far-sightedly initiated as the ‘Infant health and lifestyle survey’ by Professor Tai-Hing Lam of the University of Hong Kong and by Dr Gloria Tam of the Government Department of Health. The study was initially designed to examine the effect of primarily second-hand smoke exposure and secondarily breastfeeding on infant health and health-care utilization in the first 18 months of life. The initial study lasted for 18 months, and generated local evidence concerning the detrimental effect of second-hand smoke exposure in utero and in early life on infant health. This local evidence made an important contribution to tobacco control in Hong Kong, including the provision of evidence for the total ban on smoking in indoor workplaces and many public places in Hong Kong since 2007. With the increasing awareness of both intergenerational influences on health, and the value of evidence from non-Western contexts, the study was resurrected and reconceived in 2005 by Professor Gabriel Leung and Dr C Mary Schooling with a focus on life course epidemiology in a non-Western society. The associated fieldwork was facilitated by Drs Shirley Leung and Kwok-Hang Mak of the Department of Health. One of the motivating forces was the simultaneous realization that patterns of non-communicable chronic diseases are different from those in the West with relatively more diabetes but less breast cancer and less ischaemic heart disease (IHD), that growth patterns appeared to be different in this region, and that growth patterns, and/or exposures during growth, may have lifelong effects on health different from those usually seen in the West. Contemporaneous determinants of the noncommunicable chronic diseases (NCDs), which become more common with economic development, such as unhealthy diet, low physical activity and all their corresponding consequences, have been extensively examined and undoubtedly play the same role in nonWestern populations as elsewhere. However, diet and physical activity do not explain why the pattern of NCDs is different in this region. As has long been suggested, non-Western populations may simply be genetically more vulnerable to diabetes and perhaps to haemorrhagic stroke as well as less vulnerable to IHD and hormonally related cancers, although few candidate genes have yet been found. In developed Western settings, poor early life and/or pre-natal environments have increasingly been recognized as relevant to IHD, cardiovascular and metabolic diseases, with underlying mechanisms potentially driven by non-Mendelian inheritance. Nevertheless, these theories with cardiovascular diseases (CVD) and diabetes as a composite group are difficult to relate to disparate secular and geo-ethnic trends, or to non-Western settings where the evidence appears less compelling. Understandably perhaps, because of the lack of relevance to long-term developed populations, the socio-biology of macro-economics on intergenerational growth, development and NCDs has not received nearly as much attention. Given the very recent history of rapid economic development in this region, this gap raises the question as to the biological consequences of a hitherto overlooked aspect of economic development, i.e. upregulation of the major axes controlling growth, so obviously embodied in greater height and earlier Published by Oxford University Press on behalf of the International Epidemiological Association

Mortality associated with passive smoking in Hong Kong.

Passive smoking can cause death from lung cancer and coronary heart disease, but there is little evidence for associations with other causes of death in never smokers. A recent study showed increased all cause mortality with exposure to secondhand smoke at home but did not examine associations with specific causes of death and dose-response relations.1 We have published estimates of the mortality attributable to active smoking in Hong Kong2 and now present the related findings on passive smoking at home. Details of the sample selection and data collection have been reported.2 Each person who reported a death in 1998 at four death registries was given a questionnaire which asked about the lifestyle 10 years earlier of the decedent and of a living person about the same age who was well known to the informant. Passive smoking was identified in the interview with the question, “Ten years ago, in about 1988, excluding the decedent/control, how many persons who lived with the decedent/control smoked?” Decedents or …

Perceptions of parents and adolescent outcomes in Pakistan

The purpose of this study was to examine associations among perceived parenting variables (warmth, parental knowledge of their childs daily activities, shame induction and autonomy-granting), and psychosocial outcomes in Pakistan, a culture about which little information is available in the psychological literature. Participants were early and late adolescent Pakistani boys (N = 156) and girls (N = 148). Girls perceived their parents as being warmer, more knowledgeable about their childs activities and whereabouts, and more autonomy-granting than did boys. Warmth and parental knowledge associated with positive outcomes for girls, but not boys. Autonomy-granting associated with positive outcomes in bivariate and multivariate correlations for both genders. In causal models, perceptions of parents influenced well-being partly through the mediators of selfdenigration, positive self-image and relationship harmony, explaining up to 21% of the variance in outcomes. The results are discussed in the light of Western findings and the social context of middle-class urban Pakistan. The findings provide some support for self-determination theory, which states that autonomy-granting by parents facilitates offspring adjustment through internalization of parental values, even in non-Western cultures.