While quitting smoking delivers undeniable health benefits, researchers have found that experiencing a sharp drop in body weight after quitting may significantly increase the risk of hip fractures.
A research team led by Professors Park Ji-won, Seo Dong-hoon, and Hong Jae-young from the Department of Orthopedic Surgery at Korea University Ansan Hospital conducted a large-scale cohort study analyzing 913,805 adults aged 40 and older who underwent National Health Insurance Service (NHIS) health screenings in both 2007 and 2009. The study evaluated the correlation between post-cessation weight changes and subsequent hip fracture risk.
The study population comprised 672,858 non-smokers, 34,143 former smokers, and 206,804 active smokers. Former smokers were divided into three groups based on their weight fluctuations over a two-year period: those with a weight loss exceeding 5% (2,372 people), those who maintained their weight (23,952 people), and those with a weight gain exceeding 5% (7,816 people). Three former smokers were excluded due to missing data. Researchers tracked participants for hip fractures from 2010 through 2018, representing an average follow-up period of 8.1 years.
During the follow-up period, 6,001 participants sustained a hip fracture. After controlling for confounding variables—including age, sex, alcohol consumption, physical activity, income level, diabetes, hypertension, dyslipidemia, and chronic kidney disease—active smokers demonstrated a 1.7-fold higher risk of hip fracture compared to non-smokers.
Among former smokers, steeper weight loss correlated with a progressively higher risk of hip fracture. Compared to non-smokers, individuals who lost more than 5% of their body weight after quitting had a 1.88-fold higher risk of hip fracture. Those whose weight remained within a 5% range showed a 1.46-fold higher risk, while those who gained more than 5% exhibited a 1.61-fold higher risk.
The hip joint plays a vital role in mobility and weight-bearing support for the upper body. A hip fracture can severely impair basic daily functions such as walking or sitting, drastically reducing quality of life. In severe cases, the injury can be fatal, with previous studies indicating that 20% to 30% of hip fracture patients die within one to two years following the injury.
Maintaining a stable weight is critical for preventing hip injuries. The research team noted that weight loss reduces the mechanical stimulus required to preserve bone density, while a reduction in muscle mass impairs balance, thereby heightening the risk of falls and fractures.
The researchers added that insufficient intake of calories, protein, calcium, and vitamin D during weight loss can accelerate bone loss and sarcopenia. "Older adults, who are already at elevated risk for sarcopenia, must exercise caution to avoid rapid weight loss after quitting smoking," said Professor Park Ji-won. "Sustaining a stable weight alongside balanced nutrition is essential."
The findings were published in the international medical journal Osteoporosis International.
