Diurnal Temperature Range and Daily Cardiovascular Mortalities Among the Elderly in Hong Kong

Abstract

The authors aimed to examine the association between diurnal temperature range (DTR) and daily mortalities due to cardiovascular disease among people aged 65 years and older in Hong Kong, China. The authors used a generalized additive model to regress daily mortalities of the elderly due to cardiovascular disease on DTR and daily concentrations of air pollutants from 1997 to 2002. They also tested the effects of different lag days of DTR on mortality. Results indicate significant associations between cardiovascular mortality and DTR at lag day 1 and at lag days 0-1 to 0-5. The largest effect was at lag days 0-3 (relative risks = 1.017; 95% confidence interval = 1.003-1.031). The authors recommend that special attention be paid to the elderly population to protect them from excessive diurnal variations in temperature.

Effects of diurnal variations in temperature on non-accidental mortality among the elderly population of Montreal, Québec, 1984–2007

“…The results of these studies, shown in Table 4, are roughly in the same range, 1.37% to 2.63% change in mortality per 1˚C increase in diurnal temperature range, even if the cause of death was different: non-accidental, cardiovascular or respiratory mortality (Kan et al 2007;Tam et al 2009), chronic obstructive pulmonary disease (COPD) (Song et al 2008), coronary heart disease (CHD) (Cao et al 2009). Of interest is the large 13.9% (95%CI: 0.8 to 28.8%) percentage increase in emergency room admissions for COPD that Liang et al found to be associated to a 1˚C increase in diurnal temperature range above the 9.6 ˚C cut-off point in Taiwan (Liang et al 2009), an effect six orders of magnitude larger than the effect on daily mortality counts.…”

“…A few recent papers support the hypothesis that diurnal variations in temperature may also have a notable impact on mortality, independent of the effect of the mean temperature (Cao et al 2009;Kan et al 2007;Song et al 2008;Tam et al 2009) and robust to adjustment for air pollution (Cao et al 2009;Kan et al 2007;Song et al 2008). In Shanghai, a time-series analysis showed a 1.37% (95% CI 1.08-1.65%) increase in total non-accidental mortality, 1.86% (95% CI 1.40-2.32%) increase in cardiovascular mortality, and a 1.29% (95% CI 0.49-2.09%) increase in respiratory mortality for a 1°C increase in the 3-day moving average for diurnal temperature range (Kan et al 2007).…”

“…In a bidirectional case-crossover analysis, Cao et al (Cao et al 2009) reported a 2.13% (95% CI, 1.04% to 3.22%) increase per 1°C increase in the 2-day lagged diurnal temperature range. In Hong Kong, Tam et al (Tam et al 2009) reported a 1.7% increase in cardiovascular mortality among the elderly per 1°C increase in diurnal temperature range at lag days 0-3, while Liang et al (Liang et al 2009) found in Shanghai a 14% (95% CI, 0.8% to 28.8%) increase in the number of hospital admissions for chronic obstructive pulmonary disease with each 1°C increase in the diurnal temperature range above 9.6°C.…”

“…It has been hypothesized that, in addition to daily changes in temperature, there may be additional effects from short-term variations of temperature within the day (Cao et al 2009;Kan et al 2007;Liang et al 2009;Song et al 2008;Tam et al 2009). One such measure of within-day variability is the diurnal temperature range, which is defined by the US National Weather Service (NOAA National Weather Service 2009) as the temperature difference between the minimum at night and the maximum during the day.…”

“…Despite the burgeoning literature addressing the effects of temperature on human health, there are only a handful of papers in which the short-term effects on health of diurnal variations in temperature have been investigated (Cao et al 2009;Kan et al 2007;Liang et al 2009;Song et al 2008;Tam et al 2009). …”