Two Early Life Risk Factors for Hip Osteoarthritis

July 11, 2018

Two newly identified factors may raise the lifetime risk of symptomatic OA that requires total hip arthroplasty.

Low birth weight (LBW) and preterm birth (< 37 completed weeks’ gestation) are potential risk factors for hip osteoarthritis (OA) that requires total hip arthroplasty (THA) in adulthood, according to a recent systematic review.1

Background
Hip OA is common: symptoms develop in one in four persons. End-stage disease is treated by THA, which imposes significant financial burdens on health systems worldwide. In Australia, where this study was conducted, nearly one in eight persons eventually undergoes THA. This number has been rising steadily, with an increase of 65% from 2003 to 2015.

In developed countries, a substantial number of infants are born with LBW. In Australia, 6.2% of infants are born with LBW and 8% are born preterm. In the United States, the prevalence of LBW is 8% and preterm births is 12%. As the average age of mothers in developed countries rises, a steady increase in the number of LBW and preterm infants is also expected, since older mothers are at higher risk for delivering LBW and preterm babies than mothers aged 20 to 34 years. The survival rate of LBW and preterm infants has also increased almost 80% in the past 30 years.

The study
Hussain and colleagues at the School of Public Health and Preventative Medicine at Monash University in Melbourne, Australia, conducted a systematic literature search, which examined the available evidence for an association between OA and LBW or preterm birth. The researchers searched Ovid Medline, CINAHL, and EMBASE databases between January 1947 and August 2017.

The risk of bias was determined using the National Heart Lung and Blood Institute quality assessment tool for observational studies. Researchers then evaluated the potential causation based on the Bradford Hill criteria, commonly used to assess the adequacy of evidence for a causal relationship between an exposure and a consequence. Lastly, an economic evaluation was undertaken to estimate the costs associated with THA that are likely attributable to LBW or preterm birth in Australia.

Please click below for the findings and the implications for physicians.

The findings
Database searches identified 162 articles, but 154 were excluded after title and abstract screening because the studies did not assess hip OA in relation to LBW or preterm birth. Full-text screening was performed for eight articles, excluding three more. The five included studies consisted of two cohort, one case-control, and two cross-sectional studies.

Researchers found evidence for causation with respect to six items of the Bradford Hill criteria (consistency, strength of association, dose-response relationship, specificity, analogy, and temporal relationship), but limited or no evidence for the remaining three criteria (plausibility, reversibility, and coherence). “Overall, this approach suggests that there is modest evidence for a cause-effect relationship,” the authors conclude.

A total of 30,477 THA procedures were performed for hip OA in Australia in 2015. The proportion of study participants undergoing THA who were born with LBW or preterm was 17.3% and 19.0%, respectively. Based on these data, 5273 THA procedures performed for OA were estimated as attributable to LBW and 5791 were estimated as attributable to preterm birth. This equates to a total annual cost of AUD $132,150,222 (approximately US $98,689,786) for the LBW population and AUD $145,136,082 (approximately US $108,387,626) for the preterm population.

Implications for physicians and future research
One major limitation of this systematic review is the overall lack of available studies on this subject, though it is also important to note that research into the development and epidemiology of hip OA is generally limited despite the high burden of disease. Additional research is needed to determine the full influence of LBW and preterm birth in the pathological process of hip OA development.

Nonetheless, these calculations demonstrate a substantial implication for healthcare systems. “The full healthcare costs are likely to be significantly higher,” the authors continue, “given the additional costs of non-surgical management for less severe hip OA including pain medications and physiotherapy.” In addition, these costs will only continue to rise as the number of LBW and preterm births grows internationally with increases in maternal age.

Determining the impact of LBW and preterm birth on the development of hip OA could potentially reduce the overall burden of hip OA. Modifying the hip position of babies through postural support or perhaps “the use of double nappies” (diapers) may be beneficial. Similarly, the resurgence of swaddling in English-speaking countries may force the hips into extension and adduction, predisposing dysplasia, which could be discouraged in LBW and preterm babies. Even in the absence of overt hip changes, LBW and preterm infants could be identified as being at increased risk for hip OA and be considered for preventive strategies as evidence emerges.

References:

1. Hussain SM, Ackerman IN, Wang Y, Zomer E, Cicuttini FM. Could low birth weight and preterm birth be associated with significant burden of hip osteoarthritis? A systematic review.Arthritis Res Ther. 2018;20:121. doi: 10.1186/s13075-018-1627-7.