Impact of temperature variation between adjacent days on childhood hand, foot and mouth disease during April and July in urban and rural Hefei, China.

Previous studies have found that both high temperature and low temperature increase the risk of childhood hand, foot and mouth disease (HFMD). However, little is known about whether temperature variation between neighboring days has any effects on childhood HFMD. A Poisson generalized linear regression model, combined with a distributed lag non-linear model, was applied to examine the relationship between temperature change and childhood HFMD in Hefei, China, from 1st January 2010 to 31st December 2012. Temperature change was defined as the difference of current day's mean temperature and previous day's mean temperature. Late spring and early summer (April-July) were chosen as the main study period due to it having the highest childhood HFMD incidence. There was a statistical association between temperature change between neighboring days and childhood HFMD. The effects of temperature change on childhood HFMD increased below a temperature change of 0 °C (temperature drop). The temperature change has the greatest adverse effect on childhood HFMD at 7 days lag, with 4 % (95 % confidence interval 2-7 %) increase per 3 °C drop of temperature. Male children and urban children appeared to be more vulnerable to the effects of temperature change. Temperature change between adjacent days might be an alternative temperature indictor for exploring the temperature-HFMD relationship.

Short-term effects of extreme meteorological factors on childhood hand, foot, and mouth disease reinfection in Hefei, China: A distributed lag non-linear analysis.

BACKGROUND: Hand, foot, and mouth disease (HFMD) is a major public health issue in China with a high burden of reinfection. Previous studies presented evidence of the relationship between meteorological factors and HFMD incidence, but no study examined the effects of extreme meteorological factors on HFMD reinfection. METHODS: Daily HFMD reinfection counts and meteorological data of Hefei city were collected from 2011 to 2016. A distributed lag non-linear model was used to quantify the effects of extreme weather (wind speed, sunshine duration, and precipitation) on HFMD reinfection. All effects were presented as relative risk (RR), with 90th or 10th percentiles of meteorological variables compare with their median values. Confounding factors, such as mean temperature, relative humidity, day of week, and long-term trend were controlled. RESULTS: A total of 4873 HFMD reinfection cases aged 0-11 years were reported. Extremely high precipitation, low wind speed, and low sunshine duration increased HFMD reinfection risk. The effect of extremely high precipitation was greatest at 8 days lag (RR = 1.01, 95%CI: 1.00-1.02). Extremely low wind speed and low sunshine increased 19% (RR = 1.19, 95%CI: 1.09-1.32) and 12% (RR = 1.12, 95%CI: 1.00-1.26) risk at lag 0-12 days, respectively. By contrast, extremely high wind speed and high sunshine duration exerted certain protective effects on HFMD reinfection at lag 0-12 days (RR = 0.76, 95%CI: 0.66-0.88; RR = 0.88, 95%CI: 0.79-0.99, respectively). Subgroup analyses showed that nursery children were the most sensitive people to the extreme wind speed and sunshine duration. Children aged 4-11 years appeared to be more susceptible to extreme sunshine duration than children aged <3 years. CONCLUSION: The present study provides evidence that extreme meteorological factors exert delayed effects on HFMD reinfection. Developing an early warning system is necessary for the protection of children from harm due to extreme meteorological factors.

Short-term exposure to sulfur dioxide and the risk of childhood hand, foot, and mouth disease during different seasons in Hefei, China.

BACKGROUND: Sulfur dioxide (SO2) is an important component of air pollution, adversely impacting human health worldwide. This study aimed to examine the association between short-term exposure to SO2 and childhood hand, foot, and mouth disease (HFMD) in Hefei, China. METHODS: A Poisson generalized additive model (GAM) combining the time-series regression analyses was used to fit the SO2-HFMD association. The effect of SO2 was estimated using the single-day lag models (lag0, lag1, lag2) and the moving average lag models (lag01, lag02) We also conducted stratified analyses by season, ages (0-4 years old, 5-14 years old), gender (male, female), childcare patterns (scattered children, kindergarten children) and residence areas (urban, rural). Two-pollutant models were adopted to test the robustness of the results. RESULTS: There was a statistically significant association between SO2 and the risk of childhood HFMD. For total cases, the relative risk (RR) at lag0 was 1.038 (95% confidence interval (CI): 1.018-1.057) in whole-period and 1.088 (95% CI: 1.059-1.118) in cold season. During cold season, we observed significant associations between SO2 and HFMD among all subgroups except for children aged 5-14 years old and the adverse effects occurred on lag0, lag1, lag01, lag02. However, in hot season, SO2 were significant only for females (lag01 with RR = 1.054; 95%CI = 1.007-1.101) and scattered children (lag01 with RR = 1.054; 95%CI = 1.007-1.101). In general, females and scattered children appeared to be more vulnerable to SO2. CONCLUSIONS: This study suggests a significant association between SO2 and HFMD. especially during cold season. Compared with males and kindergarten children, females and scattered children are at higher risk of developing HFMD.

Effects of relative humidity on childhood hand, foot, and mouth disease reinfection in Hefei, China.

BACKGROUND: In recent years, hand, foot, and mouth disease (HFMD) has become a major public health issue in China, and its reinfection rate has been high. Numerous studies have examined the effects of meteorological factors involved in HFMD infection. However, no study has investigated the effects on HFMD reinfection. The present study analyzed the relationship between relative humidity and HFMD reinfection. METHODS: We employed a distributed lag nonlinear model to evaluate the relationship between relative humidity and childhood HFMD reinfection in Hefei, China during 2011-2016. This model controlled confounding factors, including seasonality, long-term trend, day of the week, precipitation, and mean temperature. RESULTS: Childhood HFMD reinfection cases occurred mainly from April to July, and the second peak occurred from October to December. A statistically significant association was observed between relative humidity and HFMD reinfection with delayed effects. The adverse effect of high relative humidity (>75%) appeared later than those of low relative humidity (<75%). Moreover, the highest relative risk (RR 1.08, 95% CI 1.04-1.13) occurred when the relative humidity was 100% and had an 8-day lag. Given the differences between gender and age groups, the effects of extremely high relative humidity on females and those aged ≥4years were higher than those of other groups and caused the highest cumulative relative risks at lag 0-9 or 0-10days (Female: RR 2.00, 95% CI 1.23-3.26; Male: RR 1.55, 95% CI 1.04-2.30; Aged ≥4years: RR 2.31, 95% CI 1.27-4.18; Aged <4years: RR 1.51, 95% CI 1.04-2.20). CONCLUSION: High and low relative humidity were found to cause the elevated risks of HFMD reinfection, and the highest risk was observed at extremely high relative humidity. Early warning systems should be built for the protection of susceptible populations, particularly females and children aged ≥4years.

Nonlinear and Interactive Effects of Temperature and Humidity on Childhood Hand, Foot and Mouth Disease in Hefei, China.

BACKGROUND: Hand, foot and mouth disease (HFMD) is one of the major infectious diseases among children and remains a health threat, especially among Asian countries. Many epidemiologic studies suggested significant association of air temperature and humidity with childhood HFMD; however, evidence on the temperature effects on childhood HFMD in temperate cities is limited, and the interactive effects of temperature and humidity have not been studied yet. METHODS: Daily counts of HFMD in children younger than 15 years of age and daily meteorologic variables during 2010 to 2012 were obtained in Hefei, China. A distributed lag nonlinear model was applied to estimate the potential nonlinear association between temperature and childhood HFMD. The interactive effects between temperature and humidity on childhood HFMD were also investigated. RESULTS: Temperature rise was associated with higher risk of childhood HFMD. Within the incubation period of HFMD, temperature rise appeared to have the acute effects on childhood HFMD, and a 5°C increase of temperature at lag 0-6 days was associated with 24.8% (95% confidence interval: 11.94%-39.10%) increase of childhood HFMD. Females and children of 0-4 years of agewere more vulnerable to temperature rise. Notably, there were obvious combined effects between temperature and humidity on childhood HFMD-the risk of childhood HFMD elevated at higher temperature and humidity level. CONCLUSIONS: This study provides evidence that temperature and humidity may jointly affect childhood HFMD, and such interactive impact needs to be considered when evaluating the temperature-childhood HFMD relationship.

Associations between extreme precipitation and childhood hand, foot and mouth disease in urban and rural areas in Hefei, China.

BACKGROUND: Understanding the relationship between extreme weather events and childhood hand, foot and mouth disease (HFMD) is important in the context of climate change. This study aimed to quantify the relationship between extreme precipitation and childhood HFMD in Hefei, China, and further, to explore whether the association varied across urban and rural areas. METHODS: Daily data on HFMD counts among children aged 0-14 years from 2010 January 1st to 2012 December 31st were retrieved from Hefei Center for Disease Control and Prevention. Daily data on mean temperature, relative humidity and precipitation during the same period were supplied by Hefei Bureau of Meteorology. We used a Poisson linear regression model combined with a distributed lag non-linear model to assess the association between extreme precipitation (≥90th precipitation) and childhood HFMD, controlling for mean temperature, humidity, day of week, and long-term trend. RESULTS: There was a statistically significant association between extreme precipitation and childhood HFMD. The effect of extreme precipitation on childhood HFMD was the greatest at six days lag, with a 5.12% (95% confident interval: 2.7-7.57%) increase of childhood HFMD for an extreme precipitation event versus no precipitation. Notably, urban children and children aged 0-4 years were particularly vulnerable to the effects of extreme precipitation. CONCLUSIONS: Our findings indicate that extreme precipitation may increase the incidence of childhood HFMD in Hefei, highlighting the importance of protecting children from forthcoming extreme precipitation, particularly for those who are young and from urban areas.