Hip fracture rate increases in winter (subtropical Australia too) – Aug 2019

Seasonality of hip fracture and vitamin D deficiency persists in a sub‐tropical climate

Internal Medicine Journal https://doi.org/10.1111/imj.14391
Sonia E. Lara Alvarez Kate Bell Nicola Ward Cameron Cooke Warrick J. Inder

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Both hip fractures and vitamin D (25‐hydroxyvitamin D (25‐OHD)) deficiency are more common in winter in regions with temperate climates, but few data exist for a sub‐tropical climate. In a South East Queensland tertiary hospital over a 7‐year period, there were significantly more hip fractures in winter than the other three seasons (analysis of variance P = 0.003), with associated higher frequency of 25‐OHD deficiency – 42.5% in winter compared to 28.5% in summer, odds ratio 1.86 (95% confidence interval 1.35–2.56), P = 0.0001. Seasonality of hip fracture and 25‐OHD deficiency occurs even in a sub‐tropical climate.

Osteoporosis and falls are risk factors for fragility fractures, particularly hip fractures in the older population. In Australia, there were over 24 000 hip fractures recorded in 2014; an ageing population and rise in chronic disease may lead to over 30 000 hip fractures per year from 2020 onwards.1 Hip fracture is associated with an increased 1‐year mortality rate of over 25%, with factors such as male sex, age, presence of heart failure and measures of functional independence being important determinants.2

Previous Australian data demonstrated a seasonal pattern for hip fractures in New South Wales3 and Victoria.4 In Geelong, Victoria, a fall in vitamin D (25‐hydroxyvitamin D (25‐OHD)) concentrations in winter was associated with increased levels of parathyroid hormone (PTH), bone resorption, falls and increased incidence of fractures both of the hip and wrist.4 Australia extends from 12 to 43°S and 115 to 151°E situated in a tropical to mild latitude world region,5 with Southeast Queensland located from 27.5°S in a sub‐tropical world region.6