{'fraction_non_alphanumeric': 0.05426917510853835, 'fraction_numerical': 0.055716353111432707, 'mean_word_length': 4.626865671641791, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
No association between gout and Alzheimer's disease: results of a case–control study in older people in Taiwan

The evidence shows that uric acid has a free-radical scavenging capacity and possesses an antioxidant effect that may reduce oxidative stress in vivo (Waring et al., 2003). Because oxidative stress is found to be involved in Alzheimer’s disease (Sultana and Butterfield, 2010), it is a plausible hypothesis that there may be a potential link between gout and Alzheimer’s disease. To elucidate this issue, we conducted a case–control study to examine whether there is an association between gout and the risk of Alzheimer’s disease in older people in Taiwan. This case–control study utilized a database from the National Health Insurance program in Taiwan. The insurance program details can be cited in the previous study (Lai et al., 2012). There were 989 subjects aged 65 years or older with newly diagnosed Alzheimer’s disease in 2000–2010 as the case group (451 men, mean age 75.9 years and standard deviation 4.9 years; and 538 women, mean age 75.8 years and standard deviation 5.0 years), according to the International Classification of Diseases 9th Revision Clinical Modification (ICD-9 codes 331.0). The index date for each case was defined as the date of diagnosing Alzheimer’s disease. We randomly selected 3956 subjects aged 65 years or older from those without Alzheimer’s disease as the control group (1804 men, mean age 75.1 years and standard deviation 5.3 years; and 2152 women, mean age 74.8 years and standard deviation 5.3 years). The case and control groups were matched with gender, age (every 5-year span) and index date. Individuals with other dementia (ICD-9 codes 290.0, 290.1, 290.2, 290.3, 290.4 and 294.1), other major psychiatric diseases (ICD-9 codes 291–293 and 295–298) or mental retardation (ICD-9 codes 317–319) were excluded from this study. In men, there were 104 subjects with gout among Alzheimer’s disease cases (23.1%) and 373 subjects with gout among control subjects (20.7%) (P= 0.27). In women, there were 75 subjects with gout among Alzheimer’s disease cases (13.9%) and 238 subjects with gout among control subjects (11.1%) (P= 0.06). After controlling for the covariates, multivariate logistic regression analysis showed that no association was detected between gout and Alzheimer’s disease in both gender (OR 0.96, 95% CI 0.74–1.25, in men; and OR 1.13, 95%CI 0.85–1.52, in women, respectively) (Table 1). As a reference of non-gout group, the sub-analysis displayed that the ORs of Alzheimer’s disease were 1.07 (95% CI 0.77–1.47) in male gouty subjects not using urate-lowering drugs and 0.82 (95% CI 0.55–1.21) in male gouty subjects using urate-lowering drugs. The ORs of Alzheimer’s disease were 1.24 (95% CI 0.87–1.76) in female gouty subjects not using uratelowering drugs and 0.98 (95% CI 0.62-1.56) in female gouty subjects using urate-lowering drugs (table not shown). A cross-sectional study by Ruggiero et al. (2009) in Italy found that patients with dementia had higher level of uric acid (P= 0.001). Another case–control study by Cascalheira et al. (2009) in Portugal found that higher level of uric acid was associated with Alzheimer’s disease (OR 2.42, P< 0.02). Both studies have conveyed the message that high level of uric acid may increase the risk of Alzheimer’s disease. In this present study, we found that no association is detected between gout and Alzheimer’s disease in both gender, whether gouty patients had ever used urate-lowering drugs or not. Because conflicting results exist, further studies are required to confirm the association between gout and Alzheimer’s disease. Some limitations should be addressed. First, because of the nature of this database, no data of uric acid could be used. Therefore, the uric acid level cannot be linked with Alzheimer’s disease in this present study. This indicates a study direction in the future for measuring uric acid when diagnosing Alzheimer’s disease. Second, we did not know what criteria were used to diagnose Alzheimer’s disease. Thus, we could not clarify the stage of Alzheimer’s disease in each patient.