Health Effects of Increasing Diurnal Temperature Range in Korea
Lim, Y.-H., Hong, Y.-C. and Kim, H. 2012. Effects of diurnal temperature range on cardiovascular and respiratory hospital admissions in Korea. Science of the Total Environment 417-418: 55-60.
Focusing on the four largest cities of Korea - the populations of which ranged from 2.5 to 9.8 million (Seoul, Incheon, Daegu and Busan) - Lim et al. were able to obtain daily hospital admission information pertaining to them from the countrywide database of the Korea National Health Insurance Corporation, which covers 97% of Korea's population. And based on these data, they assessed the effects of increasing DTR on hospital admissions for the most common cardiovascular and respiratory diseases in those four cities for the period 2003-2006, employing two different statistical approaches: "a Poisson generalized linear model (GLM) and a temperature-matched case-crossover (CC) design (Basu et al., 2005)."
According to the three South Korean researchers, the data showed that "the area-combined effects of DTR on cardiac failure and asthma were statistically significant," and that the DTR effects on asthma admissions were greater for the elderly (75 years or older) than for the non-elderly group. "In particular," as they describe it, "the effects on cardiac failure and asthma were significant with the percentage change of hospital admissions per 1°C increment of DTR at 3.0% and 1.1%, respectively." But what do such findings portend for human health under global warming?
Since it has long been known that the DTR has declined significantly over many parts of the world as mean global air temperature has risen over the past several decades (Easterling et al., 1997), it can be appreciated that the global warming with which the DTR decrease is associated (which is driven by the fact that global warming is predominantly caused by an increase in daily minimum temperature) has likely helped to significantly reduce hospital admissions for cardiac failure and asthma within the larger cities of Korea. In fact, it has likely done so for major cities all around the world, as Lim et al. note that DTR effects on non-accidental, cardiovascular, and respiratory mortality or emergency admissions have been studied in a number of Asian countries, citing the work of Cao et al. (2009), Chen et al. (2007), Kan et al. (2007), Liang et al. (2008), Liang et al. (2009), Lim et al. (2012), Shinkawa et al. (1990), Song et al. (2008) and Tam et al. (2009). And they say that each of these studies "reported a 1 to 2% increase in mortality risk per 1°C increase of DTR."
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