Andrew Y. Y. Ho

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.

Ten-year risk of osteoporotic fractures in postmenopausal Chinese women according to clinical risk factors and BMD T-scores: a prospective study.

Independent risk factors for osteoporotic fracture were identified for a Southern Chinese postmenopausal population. Clinical risk factor assessment with or without BMD measurement was shown to be an effective predictor of 10‐yr risk of osteoporotic fracture and provides a more accessible tool for patient evaluation.

Estrogen receptor β gene polymorphisms are associated with higher bone mineral density in premenopausal, but not postmenopausal southern Chinese women

Bone mineral density (BMD), the main determining risk factor for osteoporotic fractures, has a strong genetic component. Estrogen and its receptors play a critical role in both skeletal maturity and bone loss. We investigated the association between dinucleotide (cytosine-adenine; CA) repeat polymorphisms located in the flanking region of the estrogen receptor beta gene and bone mineral density (BMD) in 325 healthy southern Chinese women. BMD at the lumbar spine and hip region were measured using dual-energy X-ray absorptiometry (DEXA). The number of the repeats observed in our population ranged from 16 to 28. After adjusting for age, height, weight, and years of estrogen exposure, we observed that premenopausal subjects (n = 120) bearing at least one allele of 20 CA repeats had significantly higher BMD at the L2-4 lumbar spine (1.049 +/- 0.016 vs. 0.984 +/- 0.015; p = 0.01), total hip (0.836 +/- 0.014 vs. 0.813 +/- 0.013; p < 0.02), femoral neck (0.773 +/- 0.014 vs. 0.728 +/- 0.013; p = 0.02), trochanter (0.665 +/- 0.013 vs. 0.614 +/- 0.012; p = 0.01), and Wards triangle (0.715 +/- 0.017 vs. 0.651 +/- 0.016; p = 0.02). There was no difference in the vertebral area of L-3 and femoral neck width in these premenopausal women with or without 20 CA repeats. However, in postmenopausal women (n = 205), Estrogen receptor beta (ER beta) gene polymorphisms were not related to BMD at any skeletal site. We conclude that ER beta gene polymorphisms are associated with higher BMD in premenopausal women, suggesting that the ER beta gene may have a modulatory role in bone metabolism in young adulthood.

Determinants of peak bone mineral density and bone area in young women

Osteoporosis is a disease caused by compromised bone strength, and individuals with a high peak bone mass at a young age are likely to have a high bone mass in old age. To identify the clinical determinants of peak bone mass in young adult women, 418 southern Chinese women, aged 20–39 years, were studied. Low bone mass was defined as areal bone mineral density (aBMD) Z-score < −1 at either the spine or total hip. Within the cohort, 62 (19.0%) and 86 (26.4%) women had low aBMD at the spine and hip, respectively. Regression model analysis revealed that low body weight (<44 kg) was associated with an 8.3-fold (95% CI, 3.7–18.9) and a 6.8-fold (95% CI, 3.0–15.6) risk of having low aBMD at the spine and hip, respectively. Low body weight was also predictive of low volumetric BMD (vBMD) at the spine (odds ratio (OR) 7.8, 95% CI, 3.1–20.1) and femoral neck (OR 3.0, 95% CI, 1.3–7.1). A body height below 153 cm was associated with a 4.8-fold risk in the small L2–4 bone area (95% CI, 2.3–9.8) and a 3.9-fold risk in the small femoral neck area (95% CI, 1.9–8.1). Delayed puberty (onset of menstruation beyond 14 years) was associated with a 2.2-fold (95% CI, 1.0–4.9) increased risk of having low aBMD at the hip. Physical inactivity was associated with a 2.8-fold risk of low spine vBMD (OR 2.8, 95% CI, 1.1–6.7) and a 3.3-fold risk of low hip aBMD (95% CI, 1.0–10.0). Pregnancy protected against low spine aBMD (OR 0.4, 95% CI, 0.1–1.2) and spine vBMD (OR 0.1, 95% CI, 0.0–1.0), low femoral neck vBMD (OR 0.3, 95% CI, 0.1–1.1) and small L2–4 bone area vBMD (OR 0.3, 95% CI, 0.1–1.1). In conclusion, this study identified a number of modifiable determinants of low peak bone mass in young adult women. Maintaining an ideal body weight, engaging in an active lifestyle, and diagnosing late menarche may enable young women to maximize their peak bone mass and so reduce their risk of osteoporosis in later life.

Estimating Infection Attack Rates and Severity in Real Time during an Influenza Pandemic: Analysis of Serial Cross-Sectional Serologic Surveillance Data

This study reports that using serological data coupled with clinical surveillance data can provide real-time estimates of the infection attack rates and severity in an emerging influenza pandemic.

Transforming Growth Factor-β1 Gene Polymorphisms and Bone Turnover, Bone Mineral Density and Fracture Risk in Southern Chinese Women

Genetic contributions play an important role in determining bone mineral density (BMD) and bone turnover. Transforming growth factor-β (TGF-β) is abundant in bone and has been implicated as an important regulator of both bone formation and resorption. Several polymorphisms of the TGF-β1 gene have recently been suggested to be associated with BMD and susceptibility to osteoporotic spine fractures. To determine the relationship between TGF-β1 polymorphisms and BMD in southern Chinese women, three SNPs at C−1348-T, T29-C, and T861-20-C of TGF-β1 gene were analyzed in 237 postmenopausal southern Chinese women by RFLP and direct sequencing. BMD at the lumbar spine and hip region, biochemical markers of bone turnover, as well as serum levels of TGF-β1 were measured. Only the T29-C polymorphism of TGF-β1 gene was associated with BMD and fracture risk. The prevalence of fragility fractures was significantly higher in individuals with TC genotype (P < 0.05). Serum alkaline phosphatase and osteocalcin levels as well as urinary N-telopeptide excretion were significantly higher in women with TC than with TT or CC genotypes, and the difference remained significant after adjusting for age and BMI (all P < 0.05). Women with TC genotype had lower BMD at the trochanteric (P < 0.03) and total hip region (P = 0.05). No difference was observed in the serum TGF-β1 levels among the three genotypes. In conclusion, an association between T29-C polymorphisms of TGF-β1 gene and BMD, bone turnover as well as fragility fractures were demonstrated in postmenopausal southern Chinese women.

Efficacy and tolerability of alendronate once weekly in Asian postmenopausal osteoporotic women.

BACKGROUND: Osteoporosis has become a major health problem worldwide, and the incidence is rising in Asian countries. The aminobisphosphonates are potent inhibitors of bone resorption and are currently the mainstay of treatment for postmenopausal osteoporosis. Dosing frequency will likely affect tolerability and adherence to treatment. OBJECTIVE: To assess the tolerability and efficacy of a once-weekly aminobisphosphonate preparation in improving bone mineral density (BMD) and bone turnover markers in osteoporotic Asian women. METHODS: Chinese postmenopausal women with osteoporosis were randomized to receive either alendronate 70 mg once weekly plus calcium carbonate 500 mg daily (n = 29%) or calcium carbonate 500 mg daily (n = 29%) for one year. BMD was measured by dual energy X-ray absorptiometry. Markers of bone formation and bone resorption included plasma total alkaline phosphatase and urine N-telopeptides. RESULTS: Treatment with alendronate 70 mg once weekly for one year resulted in significant BMD improvement of 6.1% at the spine, 5.6% at the femoral neck, and 3.5% at the total hip. There was no significant change in the BMD values in the calcium group (spine 1.4%, femoral neck −0.2%, total hip 0%). The BMD response in the alendronate group was significantly different from that in the calcium group at all time points, and the difference was detectable as early as after 3 months of treatment (ANOVA p < 0.001%). The changes remained significant after adjusting for age, age at menarche, and years since menopause (p < 0.001%). Similarly, the reductions in bone markers at 12 months were significantly different between the 2 treatment groups (plasma total alkaline phosphatase: alendronate 27.9%, calcium 5.4%; urine N-telopeptide: alendronate 55.6%, calcium 11.2%; both p < 0.001%). The alendronate regimen was well tolerated, without significant adverse events. CONCLUSIONS: The results confirmed that once-weekly alendronate was efficacious in increasing BMD and reducing bone turnover and was well tolerated in Asian women.