The reasons for these deficiencies include a limited income, difficulty getting to stores, chronic illnesses or medications that interfere with nutrients, problems with chewing or digesting, and poor appetite.
A study published in 2013 by Chapman et al., has reported over 200 symptoms, for example (but not limited to) difficulty sleeping, fatigue, depression, irritability, aggressiveness, cognitive dysfunction, nausea, dizziness, tinnitus, skin irritations, nosebleeds ringing in ears, headaches, lack of concentration, vertigo and sleep disruption [ 12].
Sweat testing is further limited by difficulties in sample recovery (de la Torre and Pichini [2004]).
Even though the country has 30 million internet users, the amount of use is limited by difficulties with Chinese-language interface, a narrow range of online services and China's low per capita income.
Despite their relevance, many mid-size or small distribution companies have problems to install one of these solutions because they are either very expensive, incompatible, or limited by difficulties in data exchange.
Discussion of the success or otherwise of recruitment is usually limited and difficulties rarely expanded on.
Their use is limited with difficulties encountered in standardization and requirement of specially trained personnel.
Rural seniors' nutritional health may face greater challenges due to limited resources, difficulties with transportation, and greater distance to food resources.
Nonetheless, precise knowledge about the neural circuitry involved in tic generation is limited by difficulties de-correlating functional (neuroimaging) activity prior to and during tics (Bohlhalter et al., 2006).
Although one way to address this issue is to isolate subsets of specific cell types (for example, using cytometry or laser capture microdissection) and profile them, such techniques are expensive, time consuming and limited by difficulties in obtaining sufficient purified tissue with adequate RNA, and they may affect cell physiology and gene expression [ 20, 34].
