Interacting Factors Associated with Adult Male Drowning in New Zealand

Abstract

Objectives: i) to identify factors that contribute to the global trend of the higher incidence of male drowning relative to females, and; ii) to explore relationships between such factors from mortality data in New Zealand.

Methods: Drownings from 1983 to 2012 were examined for: Age, Ethnicity, Site, Activity, Buoyancy and Alcohol. Conditional frequency tables presented as mosaic plots were used to assess the interactions of these factors.

Results: Alcohol was involved in a high proportion of Accidental Immersion drownings (61%) and was highest for males aged 20-24 years. When alcohol was involved there were proportionally more incidences where a life jacket was Available But Not Worn and less incidences where a life jacket was Worn. Many 30-39 year old males drowned during underwater activities (e.g., snorkeling, diving). Older men (aged +55 years old) had a high incidence of drowning while boating. Different ethnicities were over-represented in different age groups (Asian men aged 25-29, and European men aged 65-74) and when involved in different activities.

Conclusions: Numerous interacting factors are responsible for male drownings. In New Zealand, drowning locations and activities differ by age and ethnicity which require targeted intervention strategies.

Fig 1. Age group affects the type of activity that precedes drowning.

The size of a cell represents the frequency of drowning deaths given the factors listed around the edges of the plot (e.g., Activity and Age Group when alcohol was/was not involved). The boundary line of the cells indicate whether the cell is larger (solid line) or smaller (dashed line) than expected if the factors were independent. The size of residuals determines the lightness of a cell: very dark grey for large residuals (> 4, corresponding to α = 0.0001), lighter grey for medium sized residuals (< 4 and > 2), white for small residuals (< 2, corresponding to α = 0.05). For example, the data for 15–19 year olds under the Water Sport / Recreation category has a colour intensity greater than 4 and a boundary line. This indicates that the proportion of cases in this category is greater than expected for this age group.

Fig 2. Most drownings occur following Accidental Immersions (i.e. falling in) and Swimming.

Over 4m refers to powerboats over 4 m in length, Under 4m refers to powerboats under 4 m in length.

Fig 3. Different ethnicities drown while engaged in different activities.

Fig 4. Age group affects the location (freshwater vs. saltwater) that precedes drowning and whether alcohol was involved.

Fig 5. The association of wearing life jackets with alcohol consumption where Power Boats were involved in drowning.