Infectious disease mortality in two Outer Hebridean islands: 2. pulmonary tuberculosis

Area of Science:

• Epidemiology
• Public Health
• Historical Medicine

Background:

• Pulmonary tuberculosis (PTB) has historically impacted populations globally.
• Understanding regional variations in PTB epidemiology is crucial for public health.
• The Outer Hebrides present a unique setting for studying historical disease patterns.

Purpose of the Study:

• To analyze mortality trends of pulmonary tuberculosis (PTB) in the Outer Hebrides (Harris and Barra).
• To compare PTB mortality patterns in the Outer Hebrides with those in Scotland overall.
• To investigate the epidemiological behavior of PTB in a remote island setting.

Main Methods:

• Retrospective analysis of death certificate data for PTB in Harris and Barra (1855-1990).
• Extraction of national PTB mortality data from Scotland's Annual Reports (1855-1990).
• Calculation of proportionate mortality ratios (PMRs) and spectral analysis, divided into pre-antibiotic and antibiotic eras.

Main Results:

• PTB mortality in Harris and Barra increased in the late 19th century, unlike Scotland's steady decline.
• Island PTB mortality patterns resembled an acute infectious disease, particularly in younger age groups.
• No correlation found between PTB mortality and socio-economic deprivation; Harris showed higher mortality in colder, wetter years.

Conclusions:

• PTB was likely uncommon in the Outer Hebrides until the late 19th century.
• The epidemiological behavior of PTB in the Outer Hebrides differed significantly from mainland Scotland.
• Findings support the hypothesis of PTB acting as an acute infectious disease in the islands, contrasting with its endemic nature in Scotland.