[The North-South difference of the relationship between cold spells and mortality risk of cardiovascular diseases in China].

Objective: To analyze the North-South difference of the relationship between cold spells and mortality risk of cardiovascular diseases in China. Methods: The time series analysis method was used to collect the daily counts of cardiovascular mortality data, meteorological data and PM2.5 concentration in the cold season (November to March of the following year) from January 1, 2013 to December 31, 2018 in 280 districts and counties in China. The non-constrained distributed lag linear model was used to analyze the relationship between cold spells and mortality risk of cardiovascular diseases and its North-South difference in China. Results: From 2013 to 2018, the mean of daily average temperature of the cold season in 280 districts and counties was 5.4 ℃. The mean of daily average relative humidity was 64.4%, and the mean of daily average PM2.5 concentration was 73.7 μg/m3. The average cold spell days in each county was 11.7 days per year,the mean of daily average temperature on cold spell days was (-2.4±6.7) ℃, and M (Q1, Q3) was -1.5 (-5.1, 1.1) ℃. The average of daily number of cardiovascular disease deaths in each county/district was (6±5) cases, and M (Q1, Q3) was 5 (2, 8) cases. The percentage change (95%CI) in the South was 4.94% (3.69%, 6.20%) (lag 0 d), higher than that in the North [the percentage change (95%CI) was 1.49% (1.14%-1.84%) (lag 0-7 d)]. In the North, the mortality risk of ≥75 years old was relatively low among three age groups, with a percentage change (95%CI) about 1.63% (1.33%-1.93%) (lag 0-21 d). In the South, the mortality risk of ≥ 75 years old was relatively high among three age groups, with a percentage change (95%CI) about 5.18% (3.78%-6.59%) (lag 0 d). Conclusion: The mortality risk of cardiovascular diseases caused by cold spells in the South is higher than that in the North of China, and the risk peak occurs earlier in the South.目的： 分析寒潮与心血管疾病死亡风险的南北差异。 方法： 使用时间序列的研究方法，收集我国280个区县2013年1月1日至2018年12月31日冷季（11月至次年3月）心血管疾病逐日死亡数据、气象资料及PM2.5浓度，采用非约束分布滞后线性模型，分析寒潮与心血管疾病死亡风险的关联和南北方的差异。 结果： 2013—2018年中国280个区县冷季日均温的均值为5.4 ℃，日均相对湿度为64.4%，日均PM2.5浓度为73.7 μg/m3；平均每个区县的寒潮日为11.7 d/年，寒潮日的日均温为（-2.4±6.7）℃，M（Q1，Q3）为-1.5（-5.1，1.1）℃；每个区县每日心血管疾病死亡例数的均值为（6±5）例，M（Q1，Q3）为5（2，8）例。南方地区寒潮与心血管疾病死亡风险百分比变化值（95%CI）为4.94%（3.69%~6.20%）（滞后 0 d），高于北方地区［百分比变化值（95%CI）为1.49%（1.14%~1.84%）（滞后 0~7 d）］。北方地区≥75岁年龄组的死亡风险较低，百分比变化值（95%CI）为1.63%（1.33%~1.93%）（滞后0~21 d）；南方地区≥75岁年龄组的死亡风险较高，百分比变化值（95%CI）为5.18%（3.78%~6.59%）（滞后0 d）。 结论： 南方地区寒潮所致心血管疾病死亡的风险高于北方地区，且南方地区风险高峰出现得更早。.