Escalating climate-related health risks for Hajj pilgrims to Mecca

Abstract

Background: Global temperatures are on the rise, leading to more frequent and severe heatwaves with associated health risks. Heat-related illnesses (HRIs) are an increasing threat for travellers to hot climate destinations. This study was designed to elucidate the interplay between increasing ambient temperatures, incidence of HRIs and the effectiveness of mitigation strategies during the annual Hajj mass gathering over a 40-year period.

Methods: An observational study was conducted utilizing historical records spanning four decades of meteorological data, and the rates of heat stroke (HS) and heat exhaustion (HE) during the Hajj pilgrimage in Mecca, Saudi Arabia. With an annual population exceeding 2 million participants from over 180 countries, the study analysed temporal variations in weather conditions over two distinct Hajj hot cycles and correlated it with the occurrence of HS and HE. The effectiveness of deployed mitigation measures in alleviating health vulnerabilities between the two cycles was also assessed.

Results: Throughout the study period, average dry and wet bulb temperatures in Mecca escalated by 0.4°C (Mann-Kendall P < 0.0001) and 0.2°C (Mann-Kendall P = 0.25) per decade, respectively. Both temperatures were strongly correlated with the incidence of HS and HE (P < 0.001). Despite the intensifying heat, the mitigation strategies including individual, structural and community measures were associated with a substantial 74.6% reduction in HS cases and a 47.6% decrease in case fatality rate.

Conclusion: The study underscores the escalating climate-related health risks in Mecca over the study period. The mitigation measures' efficacy in such a globally representative setting emphasizes the findings' generalizability and the importance of refining public health interventions in the face of rising temperatures.

Keywords: Mass gatherings; ambient temperatures; climate change; health outcomes; heat exhaustion; heat stroke; incidence; mitigation strategies; mortality; public health.

Figure 1

Temperature tends in Mecca (1985–2021). (A) Average monthly air temperatures (T_a) [top] and wet bulb temperatures (T_w) [bottom] in Mecca (1985–2021). Box plots show the median, mean (x), minimum and maximum values, and interquartile range of T_a and T_w. (B) Time series of annual mean air (top) and wet bulb (bottom) temperatures in Mecca (1985–2021) with trendiness, and values represent the average, tow-sided Mann-Kendall P-value and decadal trend.

Figure 2

Trend of average daily air (top) and wet bulb (bottom) temperatures during Hajj (1980–2021). Box plots show the median, mean (x), minimum and maximum values, and interquartile range of air temperatures (T_a) and wet bulb temperatures (T_w) during Hajj. Only average monthly T_a and T_w values were available for years 1980–1984. Shaded area represents the Hajj hot cycles [previous hot cycle (1982–1995), current hot cycle (2015–2019)].

Figure 3

Average daily wet bulb temperature in Hajj and heat stress risk levels during the study period (1980–2019). Average daily wet bulb temperature (T_w) observations during the 5 days of Hajj. Only average T_w values were available for years 1980–84. Bands indicate USNWS heat stress risk level equivalents at 45% relative humidity. Vertical dashed lines indicate bounds of Hajj periods occurring during the hot cycle [previous hot cycle (1982–1995), current hot cycle (2015–2019)].

Figure 4

Incidence of heat stroke (HS) and heat exhaustion (HE) during Hajj (1980–2019). Incidence per 100 000 pilgrims of HS [dashed line] and HE [solid line] during Hajj (1980–2019). Shaded area represents the Hajj hot cycles [previous hot cycle (1982–1995), current hot cycle (2015–2019)]. Incidence of HE for the years 1980 and 1981 were not available.

Figure 5

Case fatality rates (CFR) for heat stroke (HS) among pilgrims during Hajj (1080–2019). Bar chart representing CFR of HS among pilgrims during Hajj. *: Not reported; †: No HS cases during the pilgrimage.