Low Vitamin D May Raise Bariatric Surgery Complication Risk

Miriam E Tucker

December 31, 2015

Low vitamin D levels in bariatric surgery patients may raise the risk for adverse surgical outcomes, new US research suggests.

The findings were published online December 14 in Obesity Science & Practice by postdoctoral research fellow Leigh A Peterson, PhD, of the Johns Hopkins Center for Bariatric Surgery, Baltimore, Maryland, and colleagues.

Using nationwide inpatient data, investigators found that bariatric surgeries conducted in winter and those performed in the northern half of the country — both proxies for lower vitamin D status — were associated with higher rates of surgical complications, including dehiscence and wound infection, and longer hospital length of stay.

They note that screening patients for vitamin D status is included as part of a preoperative checklist for bariatric surgery in clinical practice guidelines cosponsored by the American Association of Clinical Endocrinologists, Obesity Society, and American Society for Metabolic & Bariatric Surgery.

However, Dr Peterson told Medscape Medical News, "this recommendation has not been widely adopted, perhaps since many surgeons rely on primary-care physicians to perform such testing."

"At our center, we send a letter requesting such labs to each primary-care physician in the hope they will screen and then treat each patient if necessary. The findings of our study strengthen the argument for preoperative screening of serum 25-hydroxyvitamin D [25(OH)D]."

Indeed, prior research by Dr Peterson and colleagues showed that 92.9% of bariatric surgery candidates had insufficient levels of vitamin D (< 30 ng/mL) and 71.4% were vitamin D deficient (< 20 ng/mL).

"We would anticipate most bariatric surgery candidates could benefit from vitamin D supplementation," said Dr Peterson.

She cautioned, however, that it's not yet clear exactly what dose of vitamin D is required to produce ideal blood concentrations (which are also unknown) for optimal outcomes in bariatric surgery.

Vitamin D Proxy Measures Correlate With Surgical Outcome

The population studied included 932,091 bariatric surgeries performed in adults aged 18 to 65 years from 2001 to 2010 in the Nationwide Inpatient Sample, which includes annual all-payer data for inpatient stays at over 1000 US hospitals.

Vitamin D status was indirectly assessed by season — based on the principle that sun exposure (photoproduction) determines the majority of vitamin D status — and by latitude, based on the principle that individuals closer to the equator have more opportunity to photoproduce vitamin D.

Just over half (51%) of the surgeries took place during spring/fall (April to June, October to December), while 26% occurred during summer (July to September) and 23% during winter (January to March). Two-thirds of procedures (64.8%) were performed at hospitals in the northern half of the country, defined as a latitude at or above 37°N (located on the east coast at Virginia Beach, Virginia).

Rates of adverse outcomes ranged from 0.01% for nonhealing wound/wound infections to 39.4% for prolonged length of hospitalization, defined as stays of more than 3 days.

After adjustment for latitude, age, sex, race, Charlson Comorbidity Index, and zip code income quartile, vitamin D seasonality was significantly correlated with suprafascial dehiscence, delayed wound healing, any complication, and prolonged length of stay.

Comparing the highest vitamin D season (summer) to the lowest (winter), odds ratios (OR) were 1.89 for suprafascial dehiscence (P = .019), 2.13 for delayed wound healing (P = .005), 2.07 for any complication (P  < .001), and 1.10 for length of stay (P < .001).

Fascial dehiscence (OR, 1.92; P = .048) was also significantly greater in the winter compared with summer even after adjustment for latitude, age, sex, and race (white vs nonwhite), while there were strong but nonsignificant similar trends for both nonhealing wounds and wound infection.

Suprafascial dehiscence, fascial dehiscence, delayed wound healing, and any complication were all significantly more likely in males. Fascial dehiscence and any complication were significantly more likely in white people.

Primary-Care Education on Need for Vitamin D Screening

Dr Peterson told Medscape Medical News that before a recommendation for presurgical vitamin D supplementation can be made, a prospective study is needed to measure preoperative 25(OH)D concentration to strengthen the case for causality in adverse surgical outcomes and to attempt to determine the desired vitamin D blood concentration required to elicit benefit.

But in the meantime, screening and treatment of vitamin D deficiency is already recommended but not widely followed.

"Education for primary-care physicians may be needed to truly improve screening of bariatric surgery candidates for vitamin D deficiency," she asserted.

Dr Peterson and the other authors had no relevant financial relationships.

Obes Sci Pract. Published online December 14, 2015. Full article

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