Age-related modification effect on the association between body mass index and the risk of hypertension: A Cohort Study on Chinese people living in the rural areas / 中华流行病学杂志

Objective: To study the modification effect of age on the association between body mass index and the risk of hypertension. Methods: People age ≥18 years old were selected by clusters, from a rural area of Henan province. In total, 20 194 people were recruited at baseline during 2007 and 2008, and the follow-up study was completed from 2013 to 2014. Logistic regression model was used to assess the risk of incident hypertension by baseline BMI and age-specific BMI. Results: During the 6-year follow-up period, 1 950 hypertensive persons were detected, including 784 men and 1 166 women, with cumulative incidence rates as 19.96%, 20.51%, and 19.61%, respectively. Compared with those whose BMI<22 kg/m(2), the RRs of hypertension were 1.09 (0.93-1.27), 1.17 (1.01-1.37), 1.34 (1.14-1.58) and 1.31 (1.09-1.56) for participants with BMI as 22-, 24-, 26- and ≥28 kg/m(2), respectively. In young and middle-aged populations, the risk of hypertension gradually increased with the rise of BMI (trend P<0.05). However, in the elderly, the increasing trend on the risk of hypertension risk was not as significantly obvious (trend P>0.05). Conclusion: The effect of BMI on the incidence of hypertension seemed to depend on age. Our findings suggested that a weight reduction program would be more effective on young or middle-aged populations, to prevent the development of hypertension.

A cohort study on body mass index and risk of all-cause mortality among hypertensive population / 中华流行病学杂志

Objective: To investigate the relationship between body mass index (BMI) and all-cause mortality in hypertensive population. Methods: All participants were selected from a prospective cohort study based on a rural population from Henan province, China. Cox proportional hazards regression models were used to estimate the associations of different levels of BMI stratification with all-cause mortality. Restricted cubic spline models were used to detect the dose-response relation. Results: Among the 5 461 hypertensive patients, a total of 31 048.38 person-years follow-up was conducted. The median of follow-up time was 6 years, and 589 deaths occurred during the follow-up period. Compared to normal weight group (18.5 kg/m(2)<BMI<24.0 kg/m(2)) the multivariate-adjusted hazard ratios for all-cause mortality associated with BMI levels (<18.5 kg/m(2), 24-28 kg/m(2), and ≥28 kg/m(2)) were 0.83 (95%CI: 0.37-1.87), 0.81 (95%CI: 0.67-0.97), and 0.72 (95%CI: 0.56-0.91), respectively. The dose-response analysis showed a nonlinear, reverse "S" shaped relationship (non-linearity P<0.001). Conclusion: Overweight or obese might have a protective effect on all-cause mortality in hypertensive population, which supports the "obesity paradox" phenomenon.

Seasonal distribution of patient hospitalization due to asthma exacerbation in 7 geographic areas in China / 中华流行病学杂志

Objective: To understand the seasonal distribution of patient hospitalization due to asthma exacerbation in 7 geographic areas in China. Methods: This was a retrospective study which involved patients hospitalized for asthma exacerbation in 29 hospitals throughout 7 geographic areas in the mainland of China (northeast, north, central, east, south, northwest and southwest). The numbers of asthmatic patients and total inpatients of the respiratory department of each hospital were recorded. The monthly ratio of asthmatic patients to the total inpatients in every area was calculated and compared. Results: During the study period, 6 480 patients were admitted for asthma exacerbation, accounting for 3.14% of all the 206 135 patients admitted to the respiratory departments in the 29 hospitals. The ratio of asthmatic patients to total inpatients in the northeast area (5.61%) was highest, and the ratio in east area was lowest (1.97%). Statistical analysis showed that the difference among different areas was significant (P<0.000 1). In most areas, both the number and proportion of hospitalized asthmatic patients peaked in spring (February-April) and autumn (September-October). In the northeast area, east area and south area, the peaks in spring were more obvious, while in the north area and southwest area, the peaks in autumn were more obvious. In the northwest area the peaks occurred in winter (December-January) and summer (June-August), respectively. The differences in hospitalization due to asthma among different months were significant in the northeast, north, and southwest areas (P<0.005). Conclusion: The number of patients hospitalized for asthma exacerbation fluctuated with season in different areas in China. In most areas, more asthmatic patients were admitted to hospitals in spring and autumn.