Influence of body fatness on the functional status in older patients with postherpetic neuralgia

Although there has been a few studies investigating the impact of increased body mass index on chronic pain disorders, the results are conflicting. In the current study, body composition such as percent body fat (PBF) was quantitatively assessed using bioelectrical impedance analysis. This study aimed to investigate the impact of the extent of body fat on the functional status in older patients with postherpetic neuralgia. Older patients, aged 50 years or above, who was diagnosed with postherpetic neuralgia were enrolled in this study. All participants underwent body composition analysis at their initial visit. Simultaneously, functional status including pain-related interference in activities of daily living (ADL), quality of life (QOL), and the emotional well-being was evaluated by questionnaires. These included the Zoster brief pain inventory, the EuroQoL-5 dimension (EQ-5D), and WHO-5 well-being index. Based on the results of body composition analysis, participants were divided into 2 groups, the normal adiposity (PBF of < 17% for men and < 32% for women) and the high adiposity group (PBF of ≥17% for men and ≥32% for women), and outcome measures were compared between 2 groups. A total of 75 participants (35 in the normal adiposity and 40 in the high adiposity group) were analyzed. Pain intensity evaluated by an 11-point numeric rating scale were comparable between the normal adiposity and the high adiposity group (4.0 [2.0-5.0] vs 4.0 [3.0-6.0], P = .374). However, a total score of Zoster brief pain inventory was higher in the high adiposity group, indicating worse performance in ADL, compared to the normal adiposity group (P = .041 by 2-tailed t-test). And the EQ VAS (0 = the worst health you can imagine, 100 = the best health you can imagine) was 70.7 ± 20.0 and 55.0 ± 23.8 in the normal and the high adiposity groups (P = .008). WHO-5 well-being index was comparable between the 2 groups (P = .082). The results of the study suggest that individuals with higher body fat may experience reduced function in ADL and decreased QoL compared to those with normal body composition, even when the severity of pain is comparable.