Association between Obesity History and Hand Grip Strength in Older Adults-Exploring the Roles of Inflammation and Insulin Resistance as Mediating Factors

Background. To examine the association between obesity history and hand grip strength, and whether the association is partly explained by subclinical inflammation and insulin resistance. Methods. Data are from 2,021 men and women aged 55 years and older participating in the representative population-based Health 2000 Survey in Finland. Body mass and body height, maximal hand grip strength, C-reactive protein, and insulin resistance based on homeostasis model assessment (HOMA-IR) were measured in a health examination. Recalled weight at 20, 30, 40, and 50 years of age were recorded to obtain a hierarchical classification of obesity history. Obesity was defined as body mass index >= 30 kg/m(2). Results. Earlier onset of obesity was associated with lower hand grip strength (p <.001) after controlling for age, sex, education, smoking, alcohol use, physical activity, several chronic diseases, and current body weight. Based on adjusted logistic regression models, the odds (95% confidence interval) for very low relative hand grip strength were 2.76 (1.78-4.28) for currently obese, 5.57 (3.02-10.28) for obese since age 01 50 years, 6.53 (2.98-14.30) for obese since age of 40 years, and 10.36 (3.55-30.24) for obese since age of 30 years compared with never obese participants. The associations remained highly significant even after adjusting for current C-reactive protein and HOMA-IR, but these variables had only minor role in explaining the association between obesity history and hand grip strength. Conclusions. Long-term exposure to obesity is associated with poor hand grip strength later in life. Maintaining healthy body weight throughout the life span may help to maintain adequate muscle strength in old age. Prospective studies with information on prior muscle strength are needed to examine in detail the causal association between obesity history and muscle strength.